why does the a/c engage with heat?

[omeara7]

Anybody know why the A/C compressor kicks on when the heat (90 degrees max heat) is turned on? Is it needed to adjust the temp to exactly 90 degrees? I pulled the A/C fuse last winter and the heat worked fine without the A/C ever kicking on. Will not having the R-134-A moving once in a while effect the a/c system at all? Thanks.

 

[SHOtimer]

The AC Compressor will run in any setting (or temp.) except "off, floor, and vent". So, if you have it on any other setting no matter what the temp the AC will run. It does this to keep the air dry and comfortable. Yes, it will dry out the system to have it just sit. An AC system should be run at least once a month....

Doug

 

[omeara7]

Thanks. That's good to know. Why would the A/C not run with flloor and vent? I thought that when I hit vent, the a/c still kicked on though???

 

[DHMag]

warm and cool air is essential for window defrosting.

 

[SHOtimer]

Thanks. That's good to know. Why would the A/C not run with flloor and vent? I thought that when I hit vent, the a/c still kicked on though???

If it is on vent and you hit "Automatic" then the AC will run. It doesn't run in those two positions so that you can have air coming in without the AC on...

Doug

 

[omeara7]

good to know-thanks. I hit vent and floor and you're right, the a/c didnt kick on. Thanks for the info.

 

[SHOtimer]

good to know-thanks. I hit vent and floor and you're right, the a/c didnt kick on. Thanks for the info.

If you do want it to turn on in one of those settings just hit the "Automatic" button.....

Doug

 

[625]

If only my climate control would do what I tell it. It prefers to send everything through the defroster vents. I have to hit the floor button, then vent, then A/C just to get the A/C to blow out of the vents. I'm guessing this has something to do with the blend door? Not too concerned about it now since I have oil leaks to fix and rod bearings to replace first. Ah, the life of the SHO owner.

Hey omeara7,
Where in Philly are you? I'm in Plymouth Meeting now. Maybe you could come over and help me with my oil leaks. Just kidding.

 

[SHOtimer]

If only my climate control would do what I tell it. It prefers to send everything through the defroster vents. I have to hit the floor button, then vent, then A/C just to get the A/C to blow out of the vents. I'm guessing this has something to do with the blend door? Not too concerned about it now since I have oil leaks to fix and rod bearings to replace first. Ah, the life of the SHO owner.

Hey omeara7,
Where in Philly are you? I'm in Plymouth Meeting now. Maybe you could come over and help me with my oil leaks. Just kidding.

The blend door IIRC has to do with the temperature of the air coming out. I think you have a vacuum issue if the air won't come out of the right place. I would run the self-test on the climate control unit and see what it tells you.

Doug

 

[DHMag]

EATC will default to defrost when vacuum is lost. ever notice that at WOT air doesnt blow thru the vents ?

 

[omeara7]

I live in Roxborough which meets Plymouth Meeting. Thats like right down the street (Ridge ave)

 

[Shoaz]

The a/c also does the job of a dehumidifier, so in any mode that a defrost function is needed it'll turn the a/c on, even when it's adding heat to the cabin.

 

[artsho]

Exactly....The AC System has a dryer...which is used to dehumidify the air.

 

[Rockledge]

The blend door IIRC has to do with the temperature of the air coming out. I think you have a vacuum issue if the air won't come out of the right place. I would run the self-test on the climate control unit and see what it tells you.

Doug

I agree with Doug about it being a vacuum issue and not a blend door/BDA issue.

The EATC test is worth running for almost any problem involving the climate control system, although in this case it may not identify the problem, since the test is really only a test of the electronics of the system, while the vacuum issue could be a mechanical one.

FWIW, I recently had the opportunity to pull the #5 fuse on my SHO which, among other things, is used for powering the EATC headunit. Sure enough, while the fuse was pulled, the climate control system would only blow warm air out the defrost vents, nothing else. That's because, as DHMag stated, when the climate control system encounters a problem, it will default to directing warm air to the defrost vents (for safety purposes).

 

[omeara7]

and like I was saying before, if you pull the a/c compressor fuse (not sure what # it is) you get heat all winter without it ever using the a/c, b/c the compressor can't get current, and heat will come out of all vents. I guess this is only a good idea if your copmressor is shot (my 92's compressor kept kicking on and off, putting major drag on the engine so I pulled the fuse and that solved my problem) But now that my 95's compressor works, I'll stick to using the vent and floor buttons to keep the compressor off, except to occasionally circulate the refrigerant/oil.

 

[Shoaz]

It's a good idea to run the a/c compressor once in a while during the winter to keep it lubed. That'll keep the compressor happier than if it sits in one position all winter.

 

[625]

EATC will default to defrost when vacuum is lost. ever notice that at WOT air doesnt blow thru the vents ?

Now that you mention it, yes. It likes to switch back to the defrost vent when the car is idling sometimes too (when vacuum is high).

Thanks everyone for the info!

(my 92's compressor kept kicking on and off, putting major drag on the engine so I pulled the fuse and that solved my problem)

That sounds like the freon is low and the low pressure switch is kicking off the compressor.

I live in Roxborough which meets Plymouth Meeting. Thats like right down the street (Ridge ave)

Hey, right down the street from me. I could hit the Plymouth Meeting mall with my bb gun from my house. (not that I would)

 

[omeara7]

That sounds like the freon is low and the low pressure switch is kicking off the compressor.QUOTE]

Yea it was but after recharging the system, the a/c still wouldn't stay on but I did get cold air and then one day....only hot air so the compressor's completely shot. I only pulled the fuse when it was still semi-working and it was winter. Not that it matters b/c the 92's sitting in my driveway now with a blown diff-pin

 

[imlosthere]

If you search the forum you can test the compressor clutch for wear. As the car gets older the clutch material wears away and creates to much of an air gap.
If you're just curious, turn on the a/c and wait for the compressor to stop. then with a long screwdriver (some people say a broom stick) tap the clutch. If it pops on it was due to the air gap. You can take off the clutch and remove one of the shims as needed.

Just FYI...

 

[omeara7]

Yea, I've read all about the air gap and how you can remove one of the spacers but the car's out of commission anyway so I'm not too worried about it. Plus its the older r-12 compressor and my 95 has r-134-a so I'm not really interested in fixing the 92's compressor. Thanks though.