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fan blower motor speed control not working
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jackx
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May 18, 2015, 2:10 PM
Post #1 of 10
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fan blower motor speed control not working
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I got a 1997 blazer. The blower fan switch does not work. It stopped working when I started it up today but after driving it about 10 miles the fan came on. I let it run a while then adjusted the fan speed to slow it down and it quit again. I pulled the dash apart and I used my voltage meter to check and it is getting power. I checked around and I believe it can either be the switch itself or the switch resistors that apparently are mounted under the hood in the fire wall next to the blower motor. How do you determine what needs to be replaced?
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Hammer Time
Ultimate Carjunky
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May 18, 2015, 4:57 PM
Post #2 of 10
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Re: fan blower motor speed control not working
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Is the motor getting a ground signal? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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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jackx
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May 18, 2015, 6:05 PM
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Re: fan blower motor speed control not working
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how do I determine if its getting a ground signal
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Hammer Time
Ultimate Carjunky
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May 18, 2015, 6:08 PM
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Re: fan blower motor speed control not working
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You can use a regular test light if you clip the wire to a power source.They make test lights that will identify either power or ground. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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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jackx
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May 19, 2015, 6:57 AM
Post #5 of 10
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Re: fan blower motor speed control not working
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I checked the ground wire to the fan with a test light and the light lite up so I guess the ground is ok. I switched it on and the fan is working now. Its been raining everyday for a week and maybe the humidity is causing the switch to act up. If it does it again I will switch the horn relay with another relay and see if the fan works then. If it does I'll get a new relay. If that doesn't fix it I will be back because I'll need some advice as to how determine what is causing the problem. If I have to replace the switch I'll need advice. I looked at it and I have no idea how its attached to the a/c switch mount housing. I do know you can buy the switch itself and you don't have to buy the entire ac switch mount. The fan sound ok but who knows. I don't have the electrical testing equipment to monitor the wave. I know its difficult to replace. You have to cut the plastic housing covering it. That's the last thing I want to do. I put some dialectic grease on the switch prongs and put the dash back together. I'm guessing if it works for a week it will be ok for a while. Thanks for the advice
(This post was edited by jackx on May 19, 2015, 7:19 AM)
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Hammer Time
Ultimate Carjunky
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May 19, 2015, 7:21 AM
Post #6 of 10
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Re: fan blower motor speed control not working
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If you want to waste a bunch of money, go ahead and use that method. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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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Discretesignals
Ultimate Carjunky
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May 19, 2015, 7:58 AM
Post #7 of 10
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Re: fan blower motor speed control not working
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Little tip.. next time the blower stops working. With the switch on high take something and smack on the blower motor. If the blower take off when you do that, you probably have a faulty blower motor. Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
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May 19, 2015, 8:01 AM
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Re: fan blower motor speed control not working
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Sport - where did you check for ground that tested good then this thing worked? Dielectric grease lasts AGES not days and both doesn't conduct electricity on its own plus it almost 100% waterproof - used for underwater things - hopefully not cars! To dry a wet connection of water the name sake WD-40 = Water Displacing FYI. With a wet (if that's real) connection that is fussy, one then the other to finish. Where you checked probably pulled on a connection or ground that IS the spot? It would test OK while working of course but whatever you wish now - leave it alone as fixed as you might have or wiggle test away where you were to cause it happen and focus on that area. Now working I doubt you need a new anything, T
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jackx
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May 19, 2015, 9:58 AM
Post #9 of 10
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Re: fan blower motor speed control not working
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I did exactly what Hammer time suggested I do and I don't plan to do anything more that will cost me cash until I figure out what is broke. The only thing that may cost money will be the switch replacement or replacing the resisters mounted in the firewall or the fan. I won't do that unless I know they are the problem. I think the suggestion from Descrete will be difficult but I will try it if the possible "free fix" of swapping the relays doesn't fix the problem if the fan stops again. The fan is covered in plastic though and I will have to carve out the plastic cover to get to the fan. Like I said I may have to do that but its the last thing I really want to do. That plastic is old and brittle and I fear it will all just crumble away. But what the heck you do what you have to do. I suspect the fan motor is the culprit. In the big picture it runs all the time. the truck has over a quarter million miles on it and its never been replaced. I'm betting if I bang on it when its not running it will come one. If so I will know it needs to be replaced As I have said I do not have the electrical equipment to test the wave so banging on it is the only way to determine if its the problem. I think I will bare the wires and test the wires to the fan first before I cut out the plastic because if its getting the right voltage the fan should run. If its getting the voltage and not running then I will know the fan is bad. Thanks for you advice I will get back if I it the fan stops running again if I need more advice.
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Hammer Time
Ultimate Carjunky
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May 19, 2015, 3:26 PM
Post #10 of 10
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Re: fan blower motor speed control not working
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If you actually did those tests correctly, then you don't need any switches or relays. You're eliminated everything but the motor if it's receiving power and ground. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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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