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Hi out there...this one comes from sweden...the land of the icebear. I have a 90 coupe and a small problem.
If i ask the EAC to give me 20 degres C, sometimes the air is hot..then its cold...then its hot...and so on. If it is cold outside, let us say it`s 10 degres and i have the roof off and i want warm air blowing araund my feet the AC blows hot air, cold air. and hot again. I want it to blow hot air all the time.
Do you undertsan the problem ??
What could be the problem ???

Welcome to CAC. You may have several things going on at one time here. You could simply have a cracked or broken vacuum supply line from the motor causing the system to not stay on the proper settting.

The actual climate control head (I assume you have automatic climate control) is a sophisticated unit and they often fail. They cost new between $150 - $200.

Finally, the actual temp control door may be sticking.

I don't know a good way to tell you how to diagnose. I would suggest you buy an actual Chevrolet Repair manual for that car including the supplementary electrical manual.

There is a good trouble shooting section there that will help you out. Otherwise we are just shooting in the dark.

One question I do have for you. Does it tend to go to the defrost position when you accelerate hard or climb hills?
No...not as i remember. But during summer it has acted strange. For example, the fan was on high speed but no air coming out. Then suddenly everything works OK, one minute later it blows hot air...and so on.
I have the HINES manual but it does not say much abaut the AC.
We have winter here now so the vette is sleeping in its garage.
But you think it is a vacum problem ???

Does the ac compressor cycle on & off?

Does the AUTO light flash for 60 seconds on the AC controller when you start the car?

Mike..abaut the compressor i do not know. As i remember the AUTO does flash and somtimes one of the other buttons. And wen i drive the car it often turns from MANUAL to AUTO.
At the moment i can not start tha car beacuse the Cluster is in Swizerland for repar.
Hi...here is something nice to look at while you are thinking ....
AC computer testing

Diagnostic Trouble codes

When the AC thinks it's in trouble,
the MODE button you have depressed
( heat, ac, auto, etc.) will flash for one minute when the car is started then go out...


Hold the arrow up & the arrow down buttons for 5 seconds the display will show 00
( to let you know your in )
Hit the Auto button
and is should scroll through the code(s) that you have

00= No problem
01= temp door motor goof
02= temp door motor goof ( different problem )
03= ambient sensor OPENED UP/disconnected
04= ambient sensor Shorted out/ kaboom
05= internal sensor OPENED UP/disconnected
06= internal sensor Shorted out/ kaboom
07= Solar sensor ( in dash ) open
09= Low gas
10= CPU has blow it's mind

After this is done...by pressing the up & down arrows you can pole the different circuts and when you find the one you are looking for
Press AUTO
and it will tell you what it thinks it sees.

To get out of Diag's

Hit defrost..( or any other AC control)

Ta Da
Yes the car is OK....
I have printed the codes, one question.....

Can i have the ignition turned on witout the cluster in place ???


Without the cluster in place.....

You mean the DASH cluster?

or the AC controller?

or both?

And if they are electrically connected but not in the correct mechanical position I think that's ok.

I men the dashcluster, vere the speedomeeter is. I had to send it
to Swizerland for repar. The AC controller is in place.
No speedo

No CCM error codes.I would wait till you get it back!

OK..i will do so. I think it will be back at the end of this week or next week. Thank`s for all your help so far and i will be back with more questions.
I think i understand a litle more abaut the troublecodes now.
I have now the dashcluster back in the car...the folloing hapend.

I turned the ignition on and there was no flashing button on the AC. I run the codes and this is the result
0 00
1 75
2 153
3 113
4 -129
5 154
6 00
7 00
9 00
10 00
11 176
12 00
16 16
17 128
19 128
20 153
21 128
22 25
23 128
24 128
30 31
31 190
34 00
35 00
36 00
37 07

That seems OK to me.

Then i turned the ignition OFF and then ON, now the button AUTO started to flash and the fan started. Wen i went to diagnostic the fan did not stopp and the values from above war complete different.
Does all this mean enything to you ??

Mike....I made a new test wen the button AUTO was flashing.
This is the result
0 02 Temp door motor
04 Ambient sensor
06 In-Vehicle sensor
08 Solar load sensor

The quetion is
Any idea is wellcome.
Try the following

Disconnect the neg side of the batt for 10 min.

This will remove all the AC errors, when you re connect the AC ( and everything else ) will go thru a self test.

Since you have the dash out this will be a good idea, then re read the errors.

Sometimes the doors loose their minds espically if the car has been sitting for a while, there is a varible resistor connected to the door to tell the computer where the doors actual position is.

( think noisy volume control on you stereo)

If the pot is not sending the correct voltage, the motor/door combo will over correct.

Try warming up the car and running thru all the AC modes.

Mike...panik...bad advise....
I disconected the battery for 15-20 minutes and conected again...
NOTHING ON THE AC WORKS, the fan is going on high speed and is not posible to turn off. No light on at eny button. No values in diagnostic. Djust 00 or -- --. I did not start the engine.
What do i do now.
Mike, panik is over. The schip is not sinking. I started the engine for one minit, i can not run it hot, the car is in the garage and has no weels on.
AND EVERYTHING SEEMS OK. I have no flashing buttons, no alarms and no errorcodes. JJJIIIIHHHHHHAAAAAAA
And all this in one evening. I have to go out with my schip untill friday then i will make a better test.
Thank`s for your help
you will hear from me again
Glad to hear that

Forgot to mention you had to start the car.

"Try warming up the car and running thru all the AC modes."

Great News


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