90 Coupe A/C Problem

[DanMoran]

I cannot get the air conditioning to work in this car. When I press the Auto button, it immediately switches to Economy. All of the other climate control functions and lights are operating OK. A mechanic has checked the freon and compressor and they are also fine. I've run through most of the diagnostics in the service manual but stopped short of accessing the ECM connections. I've determined the compressor relay is OK and I can bypass it to engage the compressor clutch, but apparently the relay is not getting the signal to activate the clutch.

Does anyone have any suggestions or advice how to proceed? We really need the A/C here in SC. Also, if it is any help, the car is red ;-)

Thanks in advance,

Dan

[Jim]

Have you cleared the codes?

Turn on the key and on your ECC ( climate control module ) push the "off" and temperature up ( up arrow ) at the same time and hold them until the car goes into the diagnostic mode. You will see all of the lights on the IPC light up and the trouble codes will then be read out where the mileage usually is.

Write down the codes as they go by. They go by pretty fast so write them down quickly and watch for the next. First you will get the engine codes eg. Exxx, then you will get the body codes eg. Bxxx then some IPC codes eg. Rxxx and maybe an SIR code.

If any code has an "h" after it that means it is a code in history and not current. No "h" means it is a current code.

After all the codes have displayed you will get a Ec? this means do you want to diagnose the engine computer. Pressing the Fan down arrow you will be telling the computer no, the fan up arrow means yes.

If you did get any Ec codes and you want to clear them, when you get the Ec? push yes and then it will ask you questions, keep pushing no until it asks if you want to clear the E codes then push yes.

If you have no E codes and/or want to go to the B codes when it asks you Ec? push the fan down button for no and it will then ask you Bc, and you can push yes. It will then ask you questions and you continue pushing no until it ask CLR b code and you push the up fan for yes.

You cannot hurt anything or screw up anything by doing this and if you make a mistake simply turn off the key and start over or push the bi-level button next to the fan switch.

[padgett]

The a/c low pressure flag is persistant. The only way I have found to clear it is to disconnect the battery for 15-20 seconds.

[Guest spongebob]

Jim, i followed you instructions, and now i want to kill myself...

im getting a 448h code and no A/C..im following the diagnosis in the manual..im at:

"check for open in CKT 721" i haver no idea what that is.

also it will tell me to "check for good terminal contact at BCM 3D16"

im confused..

also i replaced the low psi switch and have a new charge of freon..

clutch on compressor will come on, but rarely...relays arnt the problem, fuses Ok..

side note..Eo01 codes say "Hi/Lo then a mileage..

cant seem to erase anything..

[Guest spongebob]

think i found my problem..some time ago i had a code saying 4th gear switch was bad, turned out it was a short in the loom..well i grabbed that same loom and the compressor came on..jigggled it and it went off, jiggled it again and it came back on...so i have some work cut out for me finding that short..

great <img src="http://forums.aaca.org/images/graemlins/smirk.gif" alt="" />

wasnt it a short that knocked out a space mission and 3 astronaunts died?? hmmmm !!

[DanMoran]

Thank you Jim. I didn't know how important it was to clear the codes. That's all it took; the A/C is running fine now. (Boy, do I feel dumb).

I still have an intermittent problem getting into diagnostics mode however. Most of the time, when I press and hold the Off button and the Temp^ button together, the IP lights will flash but not go into diagnostic display. I seem to have more luck when the engine is running or warmed up. It took me several frustrating minutes to get into diagnostics mode before I could clear the error codes. It's probably a flaky connection somewhere. Anyone got an idea what's up there?

Is this a great forum or what!

[Guest spongebob]

Dan heres what i did (and its working so far) theres a bundle of wires

on the drivers side it runs under the teves and connects to a flat

connector on the frame. i pulled the connector apart and sprayed a

electrical spray cleaner into both 1/2s, then followed with a dielectric

grease snapped it back together..the little blue lock on mine wasnt in place

but is now..seems Buick didnt spend alot of the $35k they got for the car

on quality wiring..the wireing loom goes away also and the thin wires can rub through

to ground..

[Guest spyhunter2k]

My car is doing this as we speak! This thread just saved me the time of searching through old posts.

The problem actually first occurred about a month ago. "Service A/C" light came on, would automatically switch to Economy setting. The mechanics advised that codes just needed to be cleared.

Now it's happened again. I don't mind clearing the codes myself--it seems pretty simple. But what is making the light/error message trip in the first place? There has to be something causing this, right? Clearing the codes seems to be bypassing the symptom without addressing whatever the underlying problem is. Shouldn't this be found instead of clearing the codes only?

[Guest spongebob]

i never got a "service a/c" light, my a/c just would quit on its own and then

start back up..i did go to the codes to see if anything was there and there was,

448h...

<img src="http://forums.aaca.org/images/graemlins/smirk.gif" alt="" />

[Guest spyhunter2k]

After I clear the code, the normal A/C comes on for about 15 seconds and then the code trips again--B448c, and it switches to Economy. Anyone know what this is off the top of their head or do I need to research? Thx.

[padgett]

448 is low pressure in a/c system. According to the book that is the low side drawing down under 50 psi. I believe the low side can be monitored at BD-28 on the display but will be in degrees C not psi.

Best is to hook up a set of gauges.

[mrpushbutton]

I had an Olds Toranado Trofeo (same platform/body shell/gear) and the only problem I had with that car was the A/C. I found out that the evaporator core has poor drainage built in, the design of the box keeps the bootom of the core in its own water, which in my case (and surely in others) corroded the core and caused all of the coolant to escape. What a nightmare to replace!

[Guest spyhunter2k]

Thanks Padgett. That's what will be done.

The mechanics insisted when I took in in last time (as it seems Reattae usually require a "team approach" at most shops <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" />)that all was charged up. I'm wondering if this low pressure switch is just bad, or the BCM...

We'll see. It goes in next Thursday. 'Till then, guess I'm sweating it in the GA/FL heat.