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A/c relay and cruise control issues


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Alright, I'm fairly new to the subaru world, so please excuse my ignorance!

 

I was working on my air conditioning system in my '90 legacy (trying to find out why it was not working at all, and the compressor was not coming on!) and I first checked the low pressure switch and it was good, so then I applied 12v to the compressor and 'click' it began to spin, so then I figured that the next step would be to check the relay--- well the under hood relay/fuse compartment shows 4 a/c relays and the manual shows that they arent all just for the a/c-- some are for the fan and other such things, but the manual also shows a "main a/c relay" and i'm not sure where this is.... Could someone please tell me which one to check??? Or where to check? By the way when the car is running and the a/c button is pushed none of the relays in this compartment "click"...

 

One other question-- my cruise control has been working some days and somedays not... I push the cruise control button on the dash and I can hear the relay click and see the light on the switch comes on, but when I try to set the speed with the lever on the steering wheel nothing happens... when it is working I can hear a relay click when the the speed is set, but when it is not I do not hear the relay click... Where are these relays and what common problems do people have with this system? I checked the clutch switch and the brake switch and they appeared fine (visually) but I did not have time to take them out for a continuity test... What do you all think?

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oh yeah, I checked the clutch switch and every time it is pushed in while the cruise is on I hear a relay click under the dash, so I assume it is working properly...

 

You are correct about that. Check the switch for the brake pedal next. It may need adjusting. A common problem. You shouldn't need to remove the switch to check it out. Just measure the voltage across the switch with the igniton on and you should see a voltage change when the pedal is pressed.

 

I think the relay for the compressor is under the hood. You could try swapping relays to see if you can find a problem that way.

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On the AC, i bet you are low on AC pressure. If you have low pressure it wont run. Don't force it to run when its low on pressure as you can kill the compressor.

 

And what he said about the cruise :)

 

 

nipper

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I checked the low pressure switch (for the a/c) with my multi-meter and it showed continuity through the switch... So I think everything is fine there. Out of the four under hood relays which one is the a/c relay, or at least, the one responsible for engaging the compressor?

 

On the cruise control, If the switch on the brake pedal was not adjusted properly would it affect the brake lights-- or is there a separate switch for them?

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Get the haynes manual. The AC circuit is a bit complicated to go through here. You really do need to get pressure gauges on the AC to see what presures you have. It may be ok but you need to know that baseline.

 

Switches have contacts that can get dirty. I do beleive it has its own switch.

 

nipper

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Okay, this is what I found out today about my A/c system...

I checked all four of the relays in the under hood relay compartment (and the fuse in there too) and they all tested good. Then I checked the "air conditioning control relay" that is under the dash on the passenger side, and it tested good. So then I thought I would put a jumper wire accross the low pressure switch terminals and see if the compressor would kick on, but it did not... I did check the compressor yesterday to see if it worked by applying 12v to it and it kicked on, so I know it does work. ---- sooo, my question to you all is-- what would you check next? I don't own any fancy air conditioning tools or gauges, so what would you suggest to the average backyard mechanic to check next? I do own a haynes manual, and was thinking about checking the air conditioning control panel (buttons) to see if they were funtioning properly, but it seemed to me to be a real pain, so, I thought I would ask you all what you thought first!

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I will check tommorrow, it is getting dark now! ----I assume there is only one under the dash, the haynes manual in chapter 3 refers to it as "air conditioning control relay" --- am I correct in assuming this?

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Okay, I Checked that under dash relay for the A/C and when I push the A/C button on the dash the relay does not cick, or activate, or whatever you what to call it! I did however check the relay a couple days ago to see if it worked or not and it tested good. Here's another question-- what about the evaporator thermo-switch? I have read in the forums that alot of people have problems with it... How do you access this switch? I was looking around under the dash and I spotted the wires that go to the switch, but the switch appears to be quite hard to access! On the dash buttons, when I push the A/C button I can hear the fan come on, but none of the A/C relays activate (the main relay, or the under dash one)-- could the problem be with my A/C controls? Worn contacts or something like that? Is this vey common? Or do you Think the evaporator themo-switch would be a more likely cause? It seems like every thing else in the system is working fine- compressor, relays, lowpressure switch are all good.. what should I look at next?

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check your fuses on the fuse panel.

in addition to the fuse panel, the XT6 has a fuse for the a/c system located in the engine bay right by the relays. it's a stand alone fuse, sitting all by itself that is easy to miss or forget about. has a black cover so it doesn't stand out either. says 15A on it (15 amps). see if yours has this fuse and check it as well. i tracked down my non working a/c problem last year and checked fuses and other stuff only to find this fuse was blown...should have checked it first!

 

i would double check the relays. and make sure you didn't ruin them while testing (apply voltage to the wrong terminals).

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My info shows there is a AC relay box with 4 relays and 2 fuses in it. Do you have something like that under the hood? The switch in the evaporator may be the problem. To see if that is the problem you should be able to measure across the leads going to it and see if the switch is closed or not.

 

The AC control circuitry is pretty complicated and it may be easier to purchase a manual that covers the wiring for your car in order to try and solve this problem.

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yes, that is exactly what I have under the hood, 4 relays and 2 fuses -- and they have all been checked and rechecked again! I think that I will check the evaporator switch and then check the A/C switches themselfs and if I don't find the problem there--well, I don't know, everything else seems to be in working order! Thanks for your help, I will keep on tracking this down!

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Keep in mind when checking switches that you don't have to physically get to get to them in order to check them out. All you need to know is what wires tie to them and then use your meter to check the voltage across them. When the switch is closed it will have no voltage across it if it is ok.

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