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A/C & Cooling fan problems in 1995 Cavalier...


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95Cavy
New User

Sep 17, 2007, 4:47 PM

Post #1 of 6 (2332 views)
A/C & Cooling fan problems in 1995 Cavalier... Sign In

....just bought this car for a steal. So now I am trying to diagnose and possibly fix any problems there are.

The cooling fan (electric) and the a/c both do not work. I went so far as to short across the relays for both of them; the cooling fan started right up, and the a/c clutch engaged and the compressor started going. Now, the A/C didn't cool for **** so I know it needs a charge. I also shorted the engine temp sensor that I found on the thermostat housing (I'm pretty sure that is what turns the fan on when the radiator gets to temp, could be wrong tho) the fan did NOT turn on at that point. Also, from what I understand, the cooling fan should turn on and run continuously when the A/C is running, correct? It did not run when the A/C was running either.

Any ideas where to check next (other than an authorized mechanic, on a budget here Tongue)?

Thanks!

Rob


(This post was edited by 95Cavy on Sep 17, 2007, 4:48 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 18, 2007, 5:36 AM

Post #2 of 6 (2327 views)
Re: A/C & Cooling fan problems in 1995 Cavalier... Sign In

The fan for A/C should be on when compressor is on. Compressor will not come on if charge is too low and that's a separate issue but if you can check for even static pressure in the system it would be a start.

Cooling fan for radiator may not need to come on much. It may be fine. Not sure, but I think the temp sensing switch adds ground to make it come on at a given temp. Careful jumping things as you may cause a problem that didn't exist.

Check the pressure in the A/C for now with it just off and note the ambient temp and report back on what to do next about that,

T



95Cavy
New User

Sep 18, 2007, 4:24 PM

Post #3 of 6 (2326 views)
Re: A/C & Cooling fan problems in 1995 Cavalier... Sign In

OK, I did check the pressure (without a gauge) by releasing some pressure from the low side. Barely anything came out. So that may be why the A/C is not coming on. The cooling fan for the radiator is definately a problem because I almost overheat when sitting still and the fan still will not turn on.

Should I get a pressure guage and check the high side of the A/C?

Thanks for the help Tom!

Robert


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 18, 2007, 5:31 PM

Post #4 of 6 (2324 views)
Re: A/C & Cooling fan problems in 1995 Cavalier... Sign In

With A/C off high and low pressure should be the same. If it's not about in psi as the temp in Fahrenheit than there is almost nothing left in it and that's a problem for later and don't mess with that for now until the engine cooling fan works.

The temp switch is usually near thermostat to signal the fan for cooling the engine. Yes - it must go thru a relay to work and either of those could be the problem. Chase that down as there is no point in A/C if the engine gets destroyed overheating.

You know the motor itself works so check the relay and the switch as the most likely right now. Hit back and we can fix up the A/C which can get really involved and you will need some equipment. Avoid those kits you see that claim magic as they are not and can wreck the system when it might be a simple problem,

T



95Cavy
New User

Sep 19, 2007, 1:15 PM

Post #5 of 6 (2318 views)
Re: A/C & Cooling fan problems in 1995 Cavalier... Sign In

OK, now I'm a little confused.

First thing I did was check the voltages and ohms coming to the relay. Pin 30-12V all the time, pin 85-12V when key is on (this is to activate the relay, so the fan will only be on if the key is on), pin 86-2.5ohms, pin 87-0ohms. 30&87 are what i jumped to get the fan to start running. 85&86 are what activate the relay. 2.5ohms is stopping the relay from activating?

Also, checked the wires coming out of the temp switch on the thermostat housing. When the key is off, 0ohms and 2.5ohms. When the key is on, 4vdc shows up???? Am i checking the wrong switch? This is the only thing I can find that would be the temp switch.....am I wrong? It's the only switch by the housing....

I also swapped the cooling fan relay with the heater blower relay (same relay, same part numbers) and the blower in the car worked fine, so apparently the relay is fine....

Thanks for the help Tom!

Robert


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 20, 2007, 4:06 AM

Post #6 of 6 (2316 views)
Re: A/C & Cooling fan problems in 1995 Cavalier... Sign In

Ok: Just read back to when you were jumping relays and got everything working. Bear with me because I don't have the wiring diagrams for all cars which is out there but costs a fortune for the master package. Some have it and will share which would help right now. I have to wing it here from memory that's in my actual hard drive - my head - could be trouble!

What seems to have happened when you jumped the relay is it enabled the A/C which by itself can make the fan come on - ding, ding, ding! That kind of tells me that, that side of what prompts the fan to come on is fine. I'm about certain the A/C will not come on to protect itself as it should because there's a leak and without enough refrigerant it won't come on. Most systems sense the pressure in the A/C system with a low side switch which will be on the low side line (larger one) or the accumulator drier (aluminum can near firewall) and when pressure is below about 26 psi the A/C request will stop power to the compressor AND hence the fan. Side note: That's because even if the A/C was perfect the pressure when cold or if it was so effective it would freeze things up with frost it would cycle off and needs to as the gas (refrigerant) is likely to be a liquid and if liquid makes it to the compressor it will try to compress it and crash!! Not good - trust me. >>>>>>>>>>>>>

For a safe test let's try something....... Find that low pressure switch - it should have a green and a black wire going to it. TWO wire switch only - if more don't touch it. You can unplug that switch which gets power when A/C is requested and if pressure is up enough sends that power on to relay(s) that will engage the compressor and the fan. You can fool that switch by jumping it with like a paper clip and the A/C will think it's just ducky and time to work and I want you to do that if a two wire switch and now the fan should work when you have asked for A/C and the compressor which if for longer than a test should be unplugged as we don't want it to work now - but the system is part of the car and can't be ignored as the car would have different wiring if it was made without A/C in this car because it shares that fan.

If that works you can leave it that way and operate this car with A/C requested (or defrost will enable A/C - even the selection for defrost and floor) and the engine will stay cool and not overheat because of lack of fan. That would buy some time if you need this car to drive right now. Again - don't allow A/C compressor to work as it may be an easy fix for later and we don't want to wreck that chance.

NOW LET'S SEE IF WE CAN FIX THE DAMN FAN THE RIGHT WAY! I think either the temp sensor or the wiring from it to the relay is faulty. It's possible that we are dealing with the wrong temp sensing switch. If this car was in front of me I'd be looking for all possible, logical places an engine temp sensing switch would or could be. Because of the by-pass system of cooling systems for the engine the coolant should be about the same temp throughout so it might be elsewhere.

With that we need to find out. If looking around isn't finding it we need more help. For about $25 you can download a complete repair manual for your car from AllData.com . You and I are both on a budget for this. I don't get paid a penny for the time I spend here. I'm retired and don't work on cars anymore and am not going to spend big bucks to have info for every vehicle ever made. I understand public libraries have this version for you to look at but no doubt can't copy it but could sit there and jot down notes.

Let me know what else you can find out for this fix which is probaby quite simple but so far has escaped just what item and where has failed. Good luck,

Tom







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