I know I've seen this same problem posted before, but I can't find it anywhere. Got a 94, and the the climate control system blows only cold air until I set the control to the hottest setting which is 90 degrees. Then, and only then, does it blow hot air. Otherwise I get cold air, although it does seem a little less cold when it is set around 80 to 85, but it's definitely not hot. Maybe a door that is supposed to change the air blend is stuck?? Any help is appreciated.

 

i got EXACT the same probleme. Post me if you got any luck´. I think its my in temp censor ..:/

 

You may have a problem with your temperature door actuator. Many 90-92's have had problems with the clips, a simple part. Others have had problems with debris in the air control unit, blocking the movement of the air or of the door. It is unlikely that the door actuator is bad. I would also suggest that you trace all vacum lines from the control and programmer units. It is also possible that one of the lines has a crack or hole in it, which would make the vacum non-functional until a heavy draw (vacum) was placed on it.

Check the door actuator and rod first, then check the debris, followed by the door actuator motor, and finally the vacum lines.

 

Thanks Bob, and Devilfish, I'll keep you in mind, and let you know what I find out.

 

thanks..

Where are temperature door actuator and the air control unit placed in the car?

 

The temperature door actuator is on the passenger side, under the dash. It is directly opposite of the heating/ a/c air box. The control unit is in the dash (you see the displays) and the programmer is under the driver's side near your brake pedal, attached to the fire wall.

 

thanks

 

I'm baaaack....The car was in the shop today, the tech did all the diagnostic readings, etc. After disconnecting the battery and letting the car power down, he reconnected the battery and the system worked fine...for a short time. Then it suddenly went back to the same behavior as described in my original post. He believes it's a problem with the programmer, so now it's a matter of replacing it to see if that solves the problem., but he says he can't be sure until he tries it.

Somebody out there must have gone through this same headache!! Anybody?

 

didn't you say it does go to the hot position when you set for maximum heat?
if so then your airmix actuator is working.

i believe when you set maximum or minimum the system disregards the various sensor feedback and forces the motor to the extreme positions.

funny that the diagnostics won't tell the story

temperature sensor? airmix motor feedback? programmer?

this was my problem...

...pretty common for my vintage

paul

 

Yessir, I get hot air only when the temp control on the dash is set as high as it goes which is a reading of 90 degrees. Otherwise, I only get cold air.

 

The in side temp censor should be easy to test. Go in to diag mode, spray cooling spray on the temp censor ( passanger side vents ), and read the temp settings. If it is the same, the temp censor is bad. Havent tried this yet, but it should work.

 

During the short time the system was operating properly, temperature readings were taken at the vents and they were pretty close (within a few degrees) to the setting on the temp control, so I don't think that's the problem. As far as I can figure, it seems to be the programmer.

 

If it is the programmer Eckler's has one at a reasonable price
http://www.ecklers.com/product.asp?p...dept%5Fid=1649
and no... to those of you who are wondering, I'm not a rep for eckler's...I've just got a LOT of broken sh_t :lol: :lol: :lol: :lol:

 

89VetteWIP,
ain't it funny how we become parts experts after a few years :chevy

 

Thanks for the Ecklers info, 89VetteWIP.

John

 

PAUL -

I AGREE! WHERE DID SOME OF THE ENGINEERS COME FROM? THAT DAMN SPEEDNUT IS A ROYAL PAIN IN THE foot! MY CLIMATE CONTROL ISN'T WORKING EITHER - I GET VERY LOW BLOWER SPEED ONLY - CHECKED THE VOLTAGE GOING TO THE BLOWER MODULE UNDER THE HOOD BY THE AIRBOX AND THE VOLTAGE DOES NOT CHANGE WHEN YOU VARY THE SETTING ON MY C68 "AUTOMATIC" CLIMATE CONTROL HEAD (STAYS ABOUT 0.8v) - WAS TOLD THE PROBLEM HAD TO BE THE PROGRAMMER - GOT ONE, WENT TO INSTALL IT - THOSE DAMN ENGINEERS STRUCK AGAIN! TOOK THE SEAT OUT, THE ROOF OFF AND DID THE OLD HIGH DIVE INTO THE CAR TO GET UNDER THE DASH, AFTER YOU TAKE OFF THE CARPET UNDERDASH PANEL AND THAT DAMNED ALUMINUM CRUSH THINGIE - THE VACUUM HARNESS DOESN'T HAVE ENOUGH SLACK IN IT TO GET IT OUT FROM UNDER THE DASH, SO YOU FIGHT WITH IT "IN PLACE". COULDN'T THEY HAVE PUT AN 8MM NUT ON THERE INSTEAD OF THAT DAMN SPEEDNUT? ANYWAY, GOT THE PROGRAMMER REPLACED AND THE SYSTEM STILL DOESN'T WORK - GOT ONLY ONE OPTION NOW - FIGURE ITS GOT TO BE THE CONTROL HEAD, EVEN THOUGH IT SEEMS TO BE DISPLAYING OK AND ACTUATING THE REST OF THE VACUUM SYSTEM PROPERLY. IF I DON'T HAVE THAT PROPORTIONAL VOLTAGE TO THE BLOWER RELAY THE BLOWER WON'T WORK - THE VOLTAGE IS SUPPOSED TO COME FROM THE PROGRAMMER, BUT I GUESS IF THE PROGRAMMER ISN'T GETTING THE PROPER SIGNAL FROM THE CONTROL HEAD, THE HEAD MUST BE BAD - WHACHA THINK?

 

This is getting as good as the opti-spark threads.

 

Parts experts indeed (I think if I save all the old parts I can build a TOTALLY broken vette :rolleyes: )

No prob on the eckler's info, still working on mine

And to you opti-spark guys, at least it's only that one piece :lol: so what if it's $1200 every time a drop of water hits it JK JK JK

 

:lol: HaHa

good ones guys...

Homer,
oooooh - hated that speed nut - it currently resides way in the bush somewhere :rolleyes: i used a real nut this time :p:

yours is a '92 i believe, and since it's RPO C68 i'll assume they're the same as '89.
i wonder if you can return your new Programmer? it actually isn't involved in the Blower Fan circuit.

there is a Blower Control Module (front of dash, LH side of evaporator housing) which receives an analog signal from the Heater and A/C Control Assembly (main pushbutton/display in dash).
the Blower Control Module in turn provides an analog signal to the Blower Motor. this signal is also sent back to the Heater and A/C Control Assembly as feedback.
There is a 5 Amp Fuse in this feedback line (purple wire). when this fuse opens, the fan runs Hi speed, non stop.

Blower Control Module - do not measure RESISTANCE (ohms) on any of the C68 electronic devices! zap :eek:

The Blower Motor voltage (purple wire, same cct as feedback) should range from 4 to 12 Volts, relative to ground, depending upon the control setting (1-10)
The signal to the Blower Control Module from the Heater and A/C Control Assembly (brown wire) should range from 2.5 to 7 Volts, relative to ground.

i hope that analysing these two signals may pinpoint your problem

 

Jayvee,
once again, i'm an 89 guy so i'm assuming your system is the equvalent, control wise. though, i'm pretty sure there were physical location changes.

DO NOT measure RESISTANCE (ohms) on any of the electronic devices!
ohmmeters provide their own battery power which can zap electronic components

hmmmm, the Heater and A/C Programmer has very limited responsibility in the motor control, it just does all the hard work;
- 2 resistors and 2 transistors (maybe 2 relays instead of 2 tranistors, but it think not)

i'm pretty sure you can prove it functional or not, by putting a voltmeter across the Air Mix Valve Actuator Motor (Tan/Black and Yellow wires - 1989!)(Heater and A/C Programmer terminals M and N, if you can't get at the Motor itself),
you may then adjust the temperature to the minimum and maximum settings.
if the motor is moving (which is proof enough) you should get between 6 -12 Volts in one direction and negative 6 - 12 Volts in the other.

if you 'pass' this step, you could check the actuator's feedback while you're there;
from the Air Mix Valve Actuator is a signal wire (Green/White) which goes to the Heater and A/C Control Assembly (terminal C12).
this should range between 0 and 5 Volts. it should ramp up and down as the motor trolls back and forth.

that should prove out the Programmer and the Air Mix Valve Actuator

paul