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Honda Civic 1995 A/C won't work at hot !!


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jtz54
Novice

Jun 15, 2005, 6:29 PM

Post #1 of 37 (52253 views)
post icon Honda Civic 1995 A/C won't work at hot !! Sign In

This problem has plagued me for a year. My 95 Honda Civic Ex's A/C doesn't work at hot. Bummer in Arizona!!! Had a new compressor and condenser installed about a year ago. System worked fine for a few days then whenever the car was left in the sun the A/C won't work. Replaced clutch and fan relays, swapped in an ECU, bypassed the pressure switch, swapped in an A/C thermostat but STILL have the same problem. In the evening when it's cooled down, system works fine. When left out in the sun is when the problem really shows up. I can short the compressor clutch relay and the system will come on. The car has been back to the dealer a few times but when there it works. The freon pressure is fine and the system doesn't leak. I really thought the ECU or thermostat was the problem but was a waste of time and money. Anyone have any ideas????


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 16, 2005, 3:53 AM

Post #2 of 37 (52183 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

If messing with the clutch relay makes it come on - first just try tapping it, but I would suspect it's at fault. Try a new one. I know you said it was replaced but it could have an attitude when hot.

Can you get and post pressures while it's that hot and you make compressor run? A slight overcharge would put pressures way up when it's real hot and shut system down to protect it by a high side cutout - but would think it would kick on when you get moving along. What temps are you dealing with when parked in the sun?



jtz54
Novice

Jun 16, 2005, 7:26 PM

Post #3 of 37 (52173 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

Tom,

Thanks for replying. I did change out the relays with the same results. The problem seems to be temperature dependent. If the A/C is turned on in the morning it works most of the time. If the car is left out in 95+ degree heat then it almost never works. When it isn't working, I can short the contacts for the relay on the compressor clutch and it will come on. When it isn't working there is 12v. at both sides of the relay coils for the compressor and fan. When it is working on side of the relay coils is grounded therebye energizing the relay coil. This grounded side of the relay comes from the ECU, so the ECU is turning on or off the compressor. I thought the pressure switch might be intermittent but I shorted the contacts and eliminated that as a suspect. I did swap in another ECU and the system acted the same. At this point, I am suspecting the wires from the ECU to the compressor and fan relays. I am open to any suggestions as this car has been to the dealer a couple times but mysteriously works when they look at it (indoors, cool?). Pressure on the low side when the system is working is about 40lbs.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 17, 2005, 1:39 AM

Post #4 of 37 (52167 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

You need gauges that can do both high and low pressures. The high side can indicate problems. The kits that use low side only are NOT enough for this problem. It's only about $100 bucks to get real gauges, even at this site which is cheap in the long run. If you use them two times you are even with what it might cost for that info.

It's important info for A/C, good luck,



shrimphead
New User

Jun 28, 2005, 3:45 PM

Post #5 of 37 (52121 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

My 95 civic EX coupe has the exact same symptom!!! I swapped the ECU too. But the problem persists. I am kind of hopeless now.


motorheadII
User

Jun 28, 2005, 4:43 PM

Post #6 of 37 (52117 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

This is a bit involved, but the wire from the relay to the ECU needs to be checked for continuity at a time when the AC is NOT working. Locate the wire in the ECU harness and touch it with a test light. If the compressor engages, the wire is not at fault. It's possible the ECU is not getting an AC request signal from the HVAC control panel in the dash. Extreme interior temps could cause a switch to act up. Get a diagram and have fun chasing those circuits!
Cool


shrimphead
New User

Jun 29, 2005, 10:22 AM

Post #7 of 37 (52084 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

Thanks for the tip. But all other switches on the HVAC switches are okay during any temperature (eg recirculate, air directions,...). It makes me wonder if only the AC switch on it fails during high cabin temp. Is it possible that the AC light is on, but it actually does not close the circuit??


shrimphead
New User

Jun 30, 2005, 8:23 PM

Post #8 of 37 (52053 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

I finally fixed the problem, although I have wasted $$ to replace the ECU, thermo switch. Too bad that I did not look at the circuit diagram carefully at first. The problem is the AC switch in the HVAC. The swtich's light lights up okay, but in fact the control circuit is open when the cabin temp is high.

I pulled out the HVAC control module and tested the AC switch around sunset. It has no continuity. But when I tested in around midnight, it has continuity. So it explains the intermittent problem.

For my case, both the condenser fan and compressor won't engage duirng hot temp. But the condenser fan's operation does not depend on the ECU. So I made a mistake by swapping in a new ECU.

jtz54, have you checked out the HVAC control module? If not, you may take a look. Although the AC light is on, the connection can be bad.


jtz54
Novice

Jun 30, 2005, 8:33 PM

Post #9 of 37 (52049 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

Finally solved my problem too with the same results. The fan switch grounds the thermoswitch through the A/C switch when the blower is turned on. At hot on my car this wasn't happening. I put a temporary switch which grounded the blue/red wire going to the A/C thermostat switch and has been working fine ever since. The dealer said I could get a fan switch for $10 (special order) but recommends the entire unit (which include the A/C switch) at $120. Since you replaced your entire unit I will probably do the same. Also the dealer has 3 of these in stock so it probably gets replaced regularly. Thanks for your post!


(This post was edited by jtz54 on Jun 30, 2005, 8:35 PM)


rvdave
New User

Aug 2, 2005, 4:44 PM

Post #10 of 37 (51516 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

I want to thank you guys for inadvertenly solving a similar problem on my '92 Civic that has frustrated me for YEARS. Like yours, my A/C worked great except when it got really hot; above 90 deg the compresser clutch wouldn't actuate. While tracing the wires you discussed I noticed the connectors seemed to be very dirty and there was some corrosion. Using a toothbrush and a cup of dissolved baking soda I thouroughly cleaned all the connections, blew them dry and gave each a shot of WD-40 to displace any remaining water. For the first time in years I can hear a decisive "click" when the compresser clutch actuates. The last few days it's been very hot and the A/C has worked perfectly. If anyone else has this problem, you might want to clean the connections before replacing relays, thermostats, switches, etc. Good luck. - Dave


(This post was edited by rvdave on Aug 3, 2005, 9:15 AM)


cphillipsppl
New User

Aug 18, 2005, 11:51 AM

Post #11 of 37 (51192 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

I am also a Honda 1995 Civic owner and having the same issue with the AC not working when the car gets hot. Can you tell me exactly how to get to these wires that run to the HVAC control module so that I can try your solution.

Thanks,

CP


rvdave
New User

Aug 18, 2005, 9:22 PM

Post #12 of 37 (51177 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

CP - I'm not sure who you're directing your question to, but start at the A/C compresser clutch and work backwards. You'll run into connections at two relays and a thermostat. Make sure the connections are clean and free of corrision. I solved my problem without having to go as far as the cabin components in the dash, and hopefully you will too. Good luck. - Dave


(This post was edited by rvdave on Aug 18, 2005, 9:25 PM)


jervill
New User

Sep 5, 2005, 9:50 PM

Post #13 of 37 (50901 views)
post icon Re: Honda Civic 1995 A/C won't work at hot !! Sign In

This is sort of related and I hope someone can help.
When my 1990 Civic DX is left out in the sun ( I live in Las Vegas so temps can easily reach over 100 degrees in the summer) for four or five hours, the car will turn but will not start.
But if the car in in the shade or in the morning after a cool night, it will start with no problem.
Gets enough juice from the battery. Connections all appear to be clean. Looks like to me a resistor problem but I can use some advice so I can review and check out other angles. Hope someone can help. Let me know if you need added info.
Thanks- JV in Las Vegas


motorheadII
User

Sep 7, 2005, 12:39 AM

Post #14 of 37 (50870 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

This could be a tough one. You need to pinpoint the area causing the problem. During a no-start condition, check for fuel pressure, spark, injector control, etc.

Also, is the condition caused by sun-load heat only, or can you induce the problem by engine heat alone?


unlvboi
New User

Sep 10, 2005, 6:13 PM

Post #15 of 37 (50760 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

I am having similar problems... I live in vegas and it seems my condenser is not getting cold enough for the ac to work. I have replaced the condensor and expansion valve. and it still doesnt work. The AC WILL work if i manually cool the condesor by spraying hose water on it.... any suggestions PLEASE!!!! could it be the AC pressure switch do you think? please resond... anyone


(This post was edited by unlvboi on Sep 10, 2005, 6:19 PM)


motorheadII
User

Sep 10, 2005, 6:47 PM

Post #16 of 37 (50751 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

There's a high-pressure switch, usually located in the dryer, that prevent ac operation when high-side pressure is too extreme. If the ac works when you cool (lower the pressure) the condenser, then the switch is probably ok. I'd check the cooling fan operation and whether the system is over-charged. Look for a decal under the hood specifying the proper amount of refrigerant.


radloffe
Novice

May 14, 2006, 12:32 AM

Post #17 of 37 (47783 views)
post icon Re: Honda Civic 1995 A/C won't work at hot !! Sign In

I have a 1993 Honda civic that had a similar problem with the A/C. On a hot day, the A/C would work for a few minutes and then stop cooling, or wouldn't cool at all. Upon close inspection of the engine compartment I observed:

* when working, the A/C compressor and condenser fan would cycle on and off together.
* when HOTand NOT working, and A/C compressor would not engage, but the condenser fan would continue to cycle on and off.


I then read the above posts in this thread, and started following the circuit back form the A/C compressor. I cleaned all the contacts I could find all the way back to the firewall. No improvement.

However, I now knew where the A/C relay was. It is the right-side member of a pair of two rubber-coated relays bolted to the frame just to the right (driver's side) of the condenser. I got out some test wires (wires with flat male & female connectors on them) and my trusty electric test meter. Maybe the relay or the a/c clutch was bad, I thought.

To make a long story short, I determined that both the A/C relay and the compressor clutch were GOOD and were not the cause of the problem. The problem was the climate control unit, for some strange reason, stopped sending any signal current to the clutch relay - but only when the car was hot.

Honda quoted it as a $300+ repair. No thanks.

Since the condenser fan relay was still receiving a signal current and cycling on and off normally, I wired in a new homemade circuit that used the power sent to the condenser fan as the signal to trigger the compressor clutch relay. Both the compressor clutch and the condenser fan now cycle on and off together and the A/C is now working great. Cost me about $10 in parts, mainly 14-guage wire, wire nuts, black electrical tape and some crimp-on connectors. It actually cools better now than it ever did before. SWEET!Cool
radloffe (Amateur mechanic for 20 years)

(This post was edited by radloffe on May 14, 2006, 12:35 AM)


dnpeters
New User

May 14, 2006, 7:48 AM

Post #18 of 37 (47772 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

radloffe - I've also tried to tie the condenser fan and compressor together, but it sounds like you've been more successful than me. Did your circuit change entail bridging the two wires from the climate control unit to the two relays , or did you cut the ccu wire going to the compressor relay and connect that relay post to the ccu wire going to the condenser fan relay? Thanks for your help. - Dave


radloffe
Novice

May 14, 2006, 4:39 PM

Post #19 of 37 (47767 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

Believe it or not, I didn't have to cut into any existing wires at all... the crimp-on "standard automotive connectors" I crimped onto the new 14-gauge wires I ran were the perfect size to plug directly into the existing connectors. It was just a matter of making sure I crimped on a male connector (flat blade) or a female connector (flat blade with the ends rolled) where appropriate to match up the connector it is being plugged into.

The A/C relay has a female four-flat-blade connector running to it that looks like this:

| | - CCU signal pair. This is the low-current side that operates the relay switch (And it's the bad circuit).
| | - power pair to A/C compressor clutch, this is the high-current side that is switched by the relay. Left connector socket connects to deliver power to the compressor clutch, right is the "hot" power supply wire.

I unplugged the relay from this connector, and then plugged two short, new wires with a male & a female connector (one on each end, that I fabricated w/ crimp-on connectors), into the power pair, and then connected them to the high-current side of the relay (copper connector blades). I didn't use the CCU signal at all... I just taped over the two open sockets remaining in the connector.

THEN... there is a two-prong flat-blade connector on top of the condenser fan shroud that delivers power (hi-current) to the condenser fan. This is the circuit I used as a signal to send to the compressor relay. I unplugged this connector, then I fabricated some more wires - I cut 6 short new 14-gauge wire lengths, stripped the ends, and twisted together two sets of 3 wires with wire nuts. For each set of 3 leads, I then crimped on two female connectors and one male flat-blade connector. The male plugs into the female side of the connector providing hi-current to the condenser fan, one female connects to the male side of the connector providing power to the condenser fan, and one female connector connects to the signal side of the A/C compressor clutch relay (silver-colored connector blades). Once 3-lead set connects the "ground" side of the circuit (black wire) the other connects to the hot side (blue wire).

Tape it all down with black electrical tape so it doesn't become dislodged during normal driving. Start the car and run the A/C. Each time the condenser fan kicks on, the A/C compressor clutch will engage at the same time.

One minor "annoyance" with this setup: when the condensor fan cycles off, there is a 10-second delay before the compressor disengages. This is because as the condenser fan spins down, it's motor produces a "generator" effect that maintains current to the signal side of the Compressor clutch relay until it finishes spinning down. During this time the motor will have a very low idle for about 10 seconds (but it doesn't stall). Just an FYI... it still works fine. (way better than spending $300+, no?)
radloffe (Amateur mechanic for 20 years)


dnpeters
New User

May 14, 2006, 5:22 PM

Post #20 of 37 (47765 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

radloffe - Thanks, your instructions are very clear and match the relays and wiring on my Civic. Hopefully, I'll be able to get to this project in a few days and will report back. BTW - A 10 sec slow idle is a good trade-off for cool air in Southern California! Good luck. - Dave


radloffe
Novice

May 14, 2006, 7:41 PM

Post #21 of 37 (47762 views)
post icon Re: Honda Civic 1995 A/C won't work at hot !! Sign In

Indeed, in Omaha, NE (59 days per year above 90 degrees, 5 above 100) it's a good trade-off as well Wink.

Just be careful to:

(1) not reverse the polarity of the condenser fan... or it will run backwards and blow hot engine compartment air backwards through the condenser, and
(2) do not short any hi-current circuit across a low-current signal supply... or the CCU will be damaged (you'll also have several blown fuses to tell you if this happens)

Good luck!
radloffe (Amateur mechanic for 20 years)


rjinxd
New User

Aug 6, 2006, 4:39 PM

Post #22 of 37 (46686 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

I seem to be having a similar problem to some of the posts that I've seen here. My Civic is a '97 and during the recent onslaught of heat here in Atlanta the compressor does not engage after the car has been sitting in the sun all day, however works just fine in the morning or late evening. I have verified that the AC compressor clutch relay is fine. I shorted the terminals on the relay and the compressor kicks on. I'm guessing that this means the compressor thermal protector, clutch, and compressor itself is ok? This is as far as I have been able to troubleshoot it, the next step in my Haynes manual is to check for continuity at the plug to the compressor, but I cannot get to it from above. Next would be to check the low pressure switch which I cannot seem to get to either. From reading the previous posts though, I am really leaning towards it being the AC switch in the cabin. If anyone has any suggestions on what would be the next logical step I'd appreciate it, thanks. I do have a pair of ramps that I plan to put it onto this coming week to see if I can get a better look at the low pressure switch and compressor plug.


dnpeters
New User

Aug 6, 2006, 6:29 PM

Post #23 of 37 (46680 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

While preparing to make the above suggested wiring change, I disconnected and reconnected one of the relays (right side of radiator) and the A/C clutch actuated. I swapped the two relays (fan, clutch) and the problem was intermittent, probably because there is some common wiring that these 2 relays share. I ordered 2 new relays from hondazone.com ($60) and the problem was 90% solved, which tells me there may be more than one cause. We just got over 19 straight days of 100+ temps, and there were 3 or 4 times when the A/C wouldn't start immediately when the car was hot, but it did eventually. In my case the relays were obviously a big part of the problem. Hope this helps. Good luck. - Dave


rjinxd
New User

Aug 7, 2006, 6:48 AM

Post #24 of 37 (46680 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In

Last night I took apart my dash to get at the A/C control switch and it was extremely warm while the temperature last night was in the low 80's. I can only imagine how hot it will be this afternoon when I get in my car. According to a previous post the part costs around $110 so I am obviously a little hesitant to just change it hoping that it fixes it. When I leave work today, if it will not work I am going to try to blast the switch with cold air from a can of compressed air, if the clutch engages then I will go ahead and swap out the A/C control switch... I'll post the results later.


rodrigoscf
User

Nov 3, 2007, 6:29 AM

Post #25 of 37 (41623 views)
Re: Honda Civic 1995 A/C won't work at hot !! Sign In


In Reply To
This problem has plagued me for a year. My 95 Honda Civic Ex's A/C doesn't work at hot. Bummer in Arizona!!! Had a new compressor and condenser installed about a year ago. System worked fine for a few days then whenever the car was left in the sun the A/C won't work. Replaced clutch and fan relays, swapped in an ECU, bypassed the pressure switch, swapped in an A/C thermostat but STILL have the same problem. In the evening when it's cooled down, system works fine. When left out in the sun is when the problem really shows up. I can short the compressor clutch relay and the system will come on. The car has been back to the dealer a few times but when there it works. The freon pressure is fine and the system doesn't leak. I really thought the ECU or thermostat was the problem but was a waste of time and money. Anyone have any ideas????


Civic 93 A/C doenst cool in Idle. With 2000 RPM cool a little. The compressor clutch and system is ON! Im sure 1. Refrigerant Pressures: LOW = 45 Psi, HIGH = a bit more than 200 psi in idle.
2. Pressures below that, the A/C doesnt cool at all.
3. Dryer filter new.
4. When the car is Idle no cooling. (even in cold days)
5. When engine is at 2K RPM or above, cool a little. (cool well in cold days)
6. With the car moving around 30 MPH or above, cool a little better.(cool very well in cold days)
7. All above if I turn my A/C on with the car in low temperature and NEXT I go to a hot, sunny place.
8. If I turn my a/c on after the car was parket in sun, no cooling for a long time.
9. THe compressor clutch is engaged. The system in ON. THe car is less powerful (means the A/C compressor is ON).
10. Idle RPM from 700 to 800.
11. I put 65 psi of refrigerant... started to cool a little better, but weak yet. With 65 psi I cant accel... THe compressor goes off.
12. With 65 psi I can feel the alumunium conector freezing and with water...
13. I turned the pressure back to 45 psi. If not, the compressor would go off every second. I'm sure that the system is ON. When I push the button A/C, the green light appears, I can hear a sound of clutch engaging, I go to the engine compartment and I can see the clutch spinning, and I can feel in cold days that the system works in IDLE, but very weak. So when I have a hotter day, no cooling at all at IDLE. I'll tighten up my belt this weekend. But, beside that, Has anyone else some idea of the problem it could be? Thanks!






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