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Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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ghamilton
User
Aug 20, 2013, 9:48 AM
Post #1 of 25
(6108 views)
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Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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My son and I went and bought a truck for him a couple days ago, which is his first vehicle. He is 17 years old and only had $1000 saved up, so what he has now will require some work to get it going the way he would like.
We have a '88 Chevy 1500 Extended cab that the brake lights and turn signal lights do not work on. The front turn signal lights do work, but the rear turn signal lights do not. We have the Hayne's manual for this year of truck, but it looks like the schematics are pretty general looking. We called the seller of the truck and he said to check the brake light switch. From what I can see there is a switch that is supposed to tell when the brake pedal is fully disengaged. It looks like a bumper that the arm for the brake pedal pushes against when it is not being engaged. Then there looks like another switch that attaches via a clip to the arm for the brake pedal and it is kind of a sliding switch if I'm looking at it right. Does anybody have any pointers on the best way to test these switches to see if either or both of them are contributing to our problem with our brake and turn signal lights?
Okay, I found out some more information. For one thing, when you turn on the right turn signal, the dash indicator blinks 2 or 3 times faster than the dash indicator for the left turn signal, not sure what's up with that. Also, each tail light assy has 3 lights on it. Two of them on each side come on when the running lights are turned on and one of them comes on when you put the truck in reverse. None of them do anything when you put your foot on the brake and/or turn the turn signals in either direction. I removed the brake switch and tested it. When you depress the plunger on the switch it creates a short as it should. The weird thing though is that on the plug that connects to the switch, there is no voltage on either lead of the two-pin connector. I read on another forum that if you did not have any voltage to your switch, trace the voltage back to the fuse box and see where you lost it. Does anyone know between the light green and white wires that go to this brake switch, which one of those would be the one with the voltage? Better yet, anybody have suggestions on how I can find specific schematics for this truck or what I can check next and how?
Thanks.
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 20, 2013, 9:54 AM
Post #2 of 25
(6098 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Use a test light and test both sides of all your fuses with the key on.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ghamilton
User
Aug 20, 2013, 10:26 AM
Post #3 of 25
(6085 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Thanks. I don't have a test light, but we used a volt meter and verified all of the fuses in the fuse panel inside the truck are good. I'm not sure yet if there are more fuses under the hood, but I have not found any.
Reading in the Haynes automotive electrical manual regarding brake lights, it says "the brake lights on many vehicles use the same circuit as the rear turn signals". This is the type of circuit that we have from what I can see because each tail light assy on the back, left & right, has only 3 bulbs in each. Two of them, which are housed in red lens, are on solid anytime the running lights are turned on. One of them, which is housed in the white lens of the lens cover, comes on when we put the truck in reverse. Therefore, there are no seperate bulbs for either brakes and/or turn signals on the rear.
The manual goes on to say that "current flows from the brake light switch, through the turn signal switch and then to the brake lights". I am somewhat convinced that the absence of any voltage on either of the two wires that plug into the brake pedal switch is an indication of our problem. I just don't know where that voltage should be coming from, although I am starting to think it probably comes from the turn signal switch in the steering column and from looking at the pictures in the manual, that does not look like a place I want to go unless absolutely necessary.
I am unclear on how exactly the bulbs light up, etc. when the brake lights & turn signals are used. For example, of the two bulbs that come on when we turn the running lights on, I woud assume that one or both of these bulbs would blink when the turn signals are turned on, but really not sure what they would do when the brakes are applied. Would they burn brighter? Also, just out of curiosity, I wonder what they do when you make a turn. I know that I use my brakes sometimes during the actual turn and the turn signal does not turn off till the turn is complete. They use 3057 bulbs in them, which are dual filament bulbs if that helps any.,
Thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 20, 2013, 10:59 AM
Post #4 of 25
(6081 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Get a test light - not expensive. Yes - signals and brake light are same bulb with two filaments one the running lights and the other both brake and signals. Sockets could be messed up or plain bulbs?
Lots of trucks have trailer wiring that can mess things up too over time with inadequate wiring job that could be from a long time ago now.
Another maybe is bed of truck may have weak grounds to frame and worth a look and check if you can with back powered test light or just clean them up anyway at that age,
T
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ghamilton
User
Aug 20, 2013, 12:05 PM
Post #5 of 25
(6074 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Thanks. We will get a test light. Sounds easier to use than our volt meter. We bought a new circuit board insert for the tail light assembly which did not work either, so that covered the sockets. We had the guy at Auto Zone check out the bulbs and they are the 3057 type which is dual filament, so the bulbs are okay. We will check into the trailer wiring thing you talked about. Also, as far as the ground is concerned, there is only one plug that connects to each of the tail light assemblies and I would think that goes all the way back to the main wiring harnesses underneath the steering column, but we will trace them out to make sure a ground wire does not pop out somewhere under the frame and is not making a good connection.
Also, specifically on the wiring harness where it connects to the tail light assemblies,
Each side has a black wire in position A on the plug which I assume is ground. Each sides D position is empty. Each sides C position has a light green wire that never has any voltage on it regardless of the conditions (i.e. brake pedal pushed, turn signals turned on in either direction, truck in reverse, running lights turned on). I think this is the problem. Matter of fact, I would bet this light green wire is the same light green wire at the brake pedal switch. I’m tempted to run 12Vdc to that wire and see what happens. Hopefully I will not blow something up. In the B position, left-side tail light has a yellow wire and right-side assy has a dark green wire. These wires have varying voltage between 2 and 7.5 Vdc when the blinker is turned on. When the brake is applied, it has solid 12 Vdc and 0 V dc when not applied. Each sides E position has a dark brown wire that is solid 12 Vdc when the running lights are turned on and 0 Vdc when they are turned off. Hope this helps. Thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 20, 2013, 12:19 PM
Post #6 of 25
(6068 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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OK - get your light. Wallyworld sells them for ~$6.00 as well as NAPA (other too) to my surprise that low. You need your volt meter too but a "scratch" awl style test light (LED may be better later for something) with a wire a alligator clip and handle lights up.
Lenses on back just come off with Phillip's head screws I think. Just look then test sockets and use bulb grease in there. Even plain WD-40 would be better than nothing - it's old like ME! I drink the stuff
You may have "T" pins around now great for back probing the plug-ins for connections and bulb and tons of things. There's a lot you can test without busting the bank,
T
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ghamilton
User
Aug 20, 2013, 1:41 PM
Post #8 of 25
(6056 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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I'm with you on the test light and WD-40. I'm not really with you on the T-pins though, please explain. Thanks.
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ghamilton
User
Aug 20, 2013, 1:47 PM
Post #9 of 25
(6055 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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In the B position, left-side tail light has a yellow wire and right-side assy has a dark green wire. These wires have varying voltage between 2 and 7.5 Vdc when the blinker is turned on. When the brake is applied, it has solid 12 Vdc and 0 V dc when not applied. I thought you said you had no power at the brake light switch.......... If you have 12v at the light when the brake is applied, there is nothing wrong with the brake light circuit, except maybe a ground, bad socket or bulb.
That's a very good point. Since when we do press on the brake pedal, we do see the yellow or dark green wire transition between 0 Vdc and 12 Vdc, then that means the brake switch works and that it does have voltage going to it. So.....that must mean that either there are two switches associated with the brake pedal as hinted at that possibility in one of my previous posts, or that when I am measuring for dc voltage, maybe it is ac voltage or current that I should be measnuring. But, then again, how could you have current there without voltage? Anyway, going to auto zone to get a test light and going to see if can pay for specific schematics for this truck that I can get in my hands right now. Thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 20, 2013, 2:10 PM
Post #10 of 25
(6052 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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T-Pins ........
Not really an automotive item - more arts, crafts but just a pin. Staples or any place would have them. Plain ones would work just these are all metal so pushed in the back side while an item is attached you can test voltage or just that power or ground is there. I'm just not sure your voltmeter testing at the brake light worked well for you that's all.
You said the switch at the pedal was funky or thought so. If that wasn't pushed in when brake pedal wasn't being touched the lights if working would stay on.
You have a fast blinking signal and a slower one. I can just smell this is at the sockets or grounds or bulbs. BTW your back up light bulbs are there too. One out do it then. That # should end in a "6" just a single filament. So far this whole thing should be small beans but who knows yet?
T
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Hammer Time
Ultimate Carjunky
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Aug 20, 2013, 2:28 PM
Post #11 of 25
(6045 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Stop trying to make this something it isn't. You have power at the socket, The circuit is fine, end of story. Verify you have ground also and if you do, you have a bulb or socket problem..
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ghamilton
User
Aug 20, 2013, 4:09 PM
Post #12 of 25
(6037 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Tom, I see what you are talking about. I think I have some very small finishing nails that will do the job. I think the brake pedal switch is working, at least from the checks we have done, it looks like it is working okay, unless there is a second brake pedal switch or something. What you said about the bulbs, I am wondering, what would happen if I had a dual filament bulb in the backup light position? Could it affect whether or not the turn signals or brake lights were working properly?
Hammer Time, I guess it depends on what socket we are talking about. The positions of the connector and the resultant voltages I listed previously were at the plug that plugs into the circuit board insert of the tail light assembly, those were not readings out of the inside of the bulb sockets. When you say verify I have a ground, is it possible that I should have two grounds and that I am missing one? The light green wire in the connector that connects to both my left & right tail light assemblies is the wire I am thinking is missing whatever it is supposed to have. No matter whether the running lights are on, the brake pedal is being pushed, or if the turn signals are turned on, that light green wire never reads anything. Also if you check continuity between the black wire on that same connector to the light green wire, it shows an open. I know that black wire is at least one of the grounds to the circuit.
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 20, 2013, 4:16 PM
Post #13 of 25
(6036 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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You're making this a lot more complicated than it needs to be. You have power up to the light. See if you have it inside the light also. It's common for those light to be bad.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ghamilton
User
Aug 20, 2013, 7:21 PM
Post #14 of 25
(6026 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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That would not surprise me at all. You mean inside the socket, not the bulb, right? Anyway, we used different bulbs and installed a new tail light assy cirquit board/socket assy insert and still same thing.
I did find out a couple things though that might help lead us down the right path. First of all, that light green wire that I was wondering what it did and suspecting was not doing what it was supposed to do, well I found out it is doing what it is supposed to do. It is for the backup lights, or on the schematics B/U Lights. The very small finishing nails shoved in the back of the connectors in all pin positions helped alot in figuring this out (thanks Tom).
I also figured out that with the turn signal flashers turned on and working for the front and on the dashboard display, that when I pushed the hazard light switch, not only did the flashers stop working at all for front & dash, but the hazard lights did not work either. This makes me lean towards the turn signal switch in the steering column since I think the hazard switch is part of that switch.
I also found that the brown wire that goes to each tail light assy, left and right, that even though it measures 12 Vdc when the running lights are on, if I measure the resistance between the black (ground) and this brown wire, I measure a short between the two when we turn the running lights back off. If you look at the schematic, it shows the Left Tail / Stop / Turn Lamp has a yellow, brown and black wire going to it. The Right Tail / Stop / Turn Lamp has a dark green, brown and black wire going to it. The yellow & dark green wires are for the turn signals. The brown wire is for the running lights, and I guess they both share the same ground. For the life of me, I can't figure out why the black wire and brown wire should be shorted to each other when the running lights are off. And yes, we tried the turn signals and brake lights even when the running lights are on or off, they still don't work. Please help, I feel stupid!! Truck two, me and my son zero.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 20, 2013, 8:41 PM
Post #15 of 25
(6017 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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ghamilton: Fine finish nails are fine - whatever works for that.
As HT said don't overthink this too much. It's pretty common for trucks with the bed not grounded as it's on rubber mounts. Sockets for the bulbs common especially on the trucks and already said any especially hacked trailer wiring.
Ground straps are all over vehicles. Most just bar like this from frame metal to body metal.....
Some are covered in insulation some not?
Forget steering wheel for now especially if signal cancel when used and shut off just by turning straight again both directions. Most are/were a silly metal spring and could break. Forget that for now,
T
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ghamilton
User
Aug 21, 2013, 2:01 PM
Post #16 of 25
(6002 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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The truck bed appears to be grounded fine. Matter of fact, I traced the black wire coming out of the harness hanging from underneath the bed that feeds both of the rear tail light assemblies and found that it was just twisted to another black wire (with the union not even insulated or covered) and then that short black piece of wire was connected to the frame via a lug terminal. With the running lights on, I untwisted this junction and the running lights cutoff. Therefore, that shows me the ground for this circuit is doing what it is supposed to be doing.
I'm with you on holding off for now on the steering wheel. That is not a place I want to go unless absolutely necessary. From everything I can see, the wiring harness that feeds both rear tail light assemblies is getting exactly what it should in terms of voltage or lack thereof on each wire. Therefore, in my opinion, the obvious conclusion is that it is a problem with the bulbs or the sockets the bulbs plug into. We have verified that all of the bulbs are the dual filament 3057 bulbs and we bought a new insert for the right tail light assembly which is basically a circuit board with bulb sockets soldered onto it. When we installed this new insert, we had the same syptoms. When we turn on the running lights, they work. When we put the truck in reverse, the backup lights work. When we turn on the turn signals in either direction, whether with running lights on or off, the turn signals do not work on the rear, although they do work on the front and dash indicators. When we put on the brakes, whether the running lights are on or off, there is no indication of us pushing the brake pedal when looking at the rear of the vehicle.
Even though we have verified that all of the bulbs are dual filament bulbs and that they turn on (i.e. they work when put in the running lights positions and we turn on the running lights), I think we need to buy all new bulbs (all 6 of them), hose them down with WD-40 and insert them sternly into their sockets.
It seems like an easy problem to fix, but we are having a time of it finding what that problem is.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 21, 2013, 3:04 PM
Post #17 of 25
(5995 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Something just looking good doesn't mean it is. Ground may be inadequate and look good or weak in a wire. Bulb itself uses little for running light and 3057s are about 27 watts each so could drag down available ground.
Test those bulbs with jumper clips and force them to light. This is becoming more work than it should be IMO,
T
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Hammer Time
Ultimate Carjunky
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Aug 21, 2013, 3:19 PM
Post #18 of 25
(5991 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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You're still determined to turn this into a project that it isn't.
Will you just check for power in the bulb socket with the brake applied and we can put this whole project to rest.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ghamilton
User
Aug 21, 2013, 9:35 PM
Post #19 of 25
(5983 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Sounds like I'm wearing both of you guys out. Sorry about that. I will not post anything else till I fix it and I will let you all and the other 120 viewers know what that was. I agree it is probably easier than I am making it, but the more this goes on, it is almost getting humiliating reading the responses. Thanks.
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Tom Greenleaf
Ultimate Carjunky
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Aug 22, 2013, 2:06 AM
Post #20 of 25
(5977 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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I apologize if I've confused anything for you. Didn't re-read whole thread again.
If you have power and ground where it belongs and a bulb test good but when put in it's socket doesn't work that's where the problem is.
If no power or ground there chase that back to where it drops out - that's about it. Pretty much the back lighting on about this vintage truck is trailer wiring - that's it. If all things pass basic checks then you may need better test equipment,
T
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ghamilton
User
Aug 22, 2013, 2:24 AM
Post #21 of 25
(5969 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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I appreciate it. I will probably have to hold off till the weekend and get back into it. Thanks.
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ghamilton
User
Aug 22, 2013, 6:28 AM
Post #22 of 25
(5960 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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I took the bulb out on the right side tail light assembly, hosed it down with WD-40 and firmly re-inserted it into its socket and it started working. I tried the same thing on the left side with no success. I looked in there and although I could see 4 tabs that correspond to the leads on the bulbs, one of them was smashed in where it was not making good contact. Checking with my voltmeter, I found that the tab that was smashed in was also the one that had the pulsating voltage for the turn signals. I pried this tab out about the same distance as the other three using my DVM lead and put the bulb in there and it worked. We verified again running lights, backup lights, brake lights, turn signal lights, everything worked. Awesome!! You guys rock!!
I still don't have an explanation for why when we installed a brand new insert for the tail light assembly, it did not work, but oh well. Also, if I mentioned previously that the right-side dash indicator for the turn signals was blinking much faster than the left-side dash indicator, well now that the rear tail lights are working in all aspects, the dash board indicators are working normally now too.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 22, 2013, 7:34 AM
Post #23 of 25
(5958 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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CONGRATUALTIONS! Sorry it was a pest for you to find. Those slim contact of bulb seem inadequate to me from the get go never mind for ones that could be exposed.
Don't mess with it now working but if there again or any bulb use "bulb" grease or dialectic grease for bulbs keeping it away from the glass of course as it will last longer,
Tom
(leave this for a while but thread should be locked soon as solved and prevents spamming it or hijacking later)
(This post was edited by Tom Greenleaf on Aug 22, 2013, 7:53 AM)
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ghamilton
User
Aug 22, 2013, 2:27 PM
Post #24 of 25
(5947 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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Thanks. Will do on the dielectric grease in the future. Thanks again to you and HT for all the help.
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 22, 2013, 2:34 PM
Post #25 of 25
(5947 views)
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Re: Brake Lights & Turn Signals Do Not Work - 1988 Chevy Extended Cab Truck
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You're welcome
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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