Last year, i bought a used car (Saturn SL1) sedan. Like all used cars, it had a few things wrong. One is the air conditioning-it stays on ALL the time (except when the blower is turned off). I checked the situation, and the A/C compressor clutch is energized by a relay in the main fuse block-it gets energized (relay closes) when the blower is on-even though the A/C switch is turned off. So the engine control module is giving a signal to turn on the relay, even when the dash switch is turned off. To avoid burning the system out, I removed the relay-now no A/C. i was thinking of putting a switch on the dash (bypassing the relay), so i can control it manually. Any idea what might be wrong?
Is the front defroster turned on?
As long as you popped out the relay, go get a new one and put it in. It might just be fused closed.
Nope. The relay is fine-I took the cover off and watch it close-it works fine. As i say, it seems to be getting a signal from the ECC to turn it on-all the time.
One possibility is that the wire that goes from the relay coil to the dashboard switch is shorted to ground. This could be due to cut insulation somewhere. Tracing this down can be very difficult and requires the detailed wiring diagram that is in the manual.
Good luck!
Just to be clear, the relay is what turns the AC on and off, I know you know that, but in the OP, you were talking about putting in a switch to bypass it.
But here, you seem to think that something else is bypassing it already. The EEC is the computer, if your car is designed so the signal from the climate control is routed through the computer first, the computer would still send the on/off signal to the relay, not directly to the compressor.
Anyways, did you make sure the front defroster is turned off. Most/many cars engage the AC when you click that button, even if they don’t turn on the light that tells you the AC is running.
If defrost is off, you might also try turning off recirculate, just for kicks.
I just put the relay back in-as I say A/C is always on-as long as the fan in running. The clutch de-energizes when the fan is off. So i guess there is short somewhere-it stays on in recirculate mode, in defrost, and in cabin air mode. So I guess I’m OK as long as I don’t use the blower. I’ll have to live with it (and take the relay out in winter). I think this is a problem that an A/C shop would charge a lot to fix.
It should turn on when you’re using defrost. Check you’re manual, as it may turn on while in recirculate. Both of these are by design, even while in heating mode, to keep the cabin air dry. Otherwise the windows will fog up due to your breath giving off moisture and the windows being cold.
If you have the windshied defroster off AND it’s set to bring in fresh air from the outside AND the AC button is off AND the AC is still running then you need to start troubleshooting. First, make sure all those settings are, well, set that way.
Like I said before, on many cars, even if the AC is running because something else is calling for it (like the defroster) it won’t necessarily turn the AC light on, leading a lot of people to think something is wrong. I’ve had friends ask me to look at their car with this exact complaint and I know we’ve had threads about it over the years.
ETA, I’m not saying you’re wrong or that something isn’t broken, I just want to make sure we eliminate it working properly in a way you’re not expecting first. Otherwise you’re going to spend a lot of time hunting down a problem that doesn’t exist.
I think Joey is right, understanding the operation is always the first step.
I checked again-the A/C switch light is always illuminated-even when in heat, cabin air, recirculate, or defrost mode. This should not be. The only time it is off is when the fan is off. My main concern is for the longevity of the A/C clutch.
If it won’t shut off in any mode except when the blower is turned off, and the relay is good, the next thing to check is the A/C switch. If it’s stuck on the symptom would be exactly as described.
ETA: Given post #9, I’d bet money it’s a faulty A/C switch.
Either you wrote that wrong or you don’t understand what I’ve been trying to explain.
Does the AC run with defrost, recirculate, AC all turned off?
Also, I’m not sure what you mean when you say ‘cabin air’. Do you mean ‘fresh air’. The one with the picture of air coming in from the outside? The opposite of recirculate?
Yes, the A/C switch is always lit-it has two positions- one where the system automatically turns the A/C on, and one where you manually turn it on-it is always on. Whether I turn the recirculate air on or off, it (the A/C) is on. If I turn the system to fresh air, it remains on-high or low temp., it doesn’t matter. According to the owners manual, it (the A/C) should be off in fresh air mode. This A/C system is pretty simple-it has no outside temp. sensor-it is (I guess) semi-automatic. So I conclude that the ECC is giving a wrong input to the relay, and turning it on. If this is the case, i don’t see how I could fix it.
One oddball problem with a/c I solved on time was where the groundwire for the a/c grounded at the starter. When they changed the starter they hooked it up to a positive post, instead of shorting out it simply ran all the time.
See if you can get a schematic and you may find something that has had human contact at one time or another in the past that may have been reversed.
What year is yours? I think only maybe the very last of the SL1’s would have had a computer controlled HVAC system.
But either way, if the switch is staying illuminated when it’s supposed to be off that pretty strongly suggests the problem is the switch itself.
MY2003. If the switch is shorted, that might explain it. Since the blower motor switch is in series with the A/C switch, this explains why the A/C is off when the blower is off…but still doesn’t explain why the relay is always energized.
If the A/C clutch is disengaging when you turn the blower off, the relay can’t be energized. What makes you think it is? Keep in mind it’ll always have 12v going to one side of it.
I have the same car. Don’t have this problem though. Whenever I’ve had a problem the Saturn fans forum members have been able to pretty much diagnose everything and give me videos and diagrams, etc. I am not a “car guy,” and that might not be necessary for general issues, but for make/model specific issues (for example a couple sensors that always go bad in this model) that has been a lifesaver.
He said the blower motor and AC switch are in series. I don’t know how he knows this but it makes sense. Even with everything working properly, it would make sense that if the blower motor is set to Off, you wouldn’t want the compressor to be able to run. Otherwise the coils would freeze.
An easy way to make that happen would be to feed the AC switch from the blower speed switch.
I doubt you can buy just the switch, but the whole panel looks pretty cheap. The problem is going to be the hours and hours you’re going to spend tearing apart your dash to drop the new one in. But I’m sure you can find plenty of videos on how to do that.
If you really don’t mind putting in your own switch, go ahead. Tear out the old one and just reuse the wires (if you have room to work with them). Keep in mind, it’s going to kill the resale value. Also, if possible, I’d try to put the new switch on the climate control panel (or even just hanging from wires under the dash) so if a new owner does want to fix it, they don’t have a hole in dashboard somewhere.
I think I’m going to just keep the relay in (in the summer) and keep the blower off. I doubt I can get a new switch easily, so i guess I’ll live with it.