ke4mns

hi, all just got a 91 c4 its in decent space but has its 20 yo problem i need to fix them one at a time, 1st thing i want to tackle is the heater ac problem,the heater works great but the temp of the heat dont modulate,the digital read out does not show the correct os air temp,and when ya turn it to 60 it does not kick on the ac so can ya help me with this problem ,mark

CorvetteMike2024

r u texting this message i realy dont like 2 respond to texting messages when they r writen in texting format its hard 4 me to understand what u r sayin.

Since you are new, Welcome. Try the search function here. It has lots of good info. Its hard for me to understand whats going on with your car. Sounds like you might have issues with your blend door. If you have the C68 electronic HVAC controls, you may be able to pull the trouble codes from the unit its self. Maybe someone else will chime in with more help.

Good Luck

Mike

ke4mns

no i wasnt writing txt and it dont look like txt,but would it be the door if ya turned it to 60 and the ac wont come on im thinkin the controller mite be having a problem but i dont know thats why im askin

CorvetteMike2024

looks like texting 2 me im done here good luck maybe someone who likes 2 txt can help u

DavePlum

Please explain what you have done to troubleshoot this problem so far. And like Mike said, you'll likely get a better response if you don't write in a texting manner. Some people don't understand or care for texting on a forum. I for one am confused as to how the heater could be working great but the temp of the heat doesn't (modulate) change?

If your planning on keeping this car the best advice I can give you is to get a FSM and let the fun begin! Good luck.

ke4mns

I dont know what your talking about txt manner?what is it i just dont have all the periods and comma in the proper place?What i mean but heater working good is that the heat is coming out all vents fine.Its cold here so its working fine, One thing i noticed last nite was the lites on the postions were blinking,

NebCorvette94

Take a pic if you could, on the radator are two fans. I beleve the one on the left, when your seated, is always on, and the one on the right kicks on when you use the AC, or the vettes temp gets to high. Does the fan turn on, when you turn on AC.

FSM
http://www.helminc.com/helm/homepage...x=&startPage=1



"the digital read out does not show the correct os air temp" How far off is the outside air temp.

ke4mns

The car isnt over heating.Ok the heater control works as long as its in heat mode but if ya turn down the control to like 70 degrees the temp of the air coming out will not cool down its like its not closing the heater control valve on the engine.Then when i turn it down to 60 degrees which should kick the ac on the heat still come out the vents,now it will completely shut off when the off button is depressed .what im thinking is that its the delco control on the dash but if its like the control valve i dont want to buy a 250 control when it could be a 30 dollar valve

ke4mns

Oh and the outside air temp is all over the plce but its reading 50-60 degrees and its in the 20s around here

NebCorvette94

Does the second fan click on, when your lowering the temp.

CorvetteMike2024

u really should buy a fsm it will stop the guessin and wil tel u whats going on with ya car. u can find them on ebay money we spend i have a 89 fsm and if you can use proper writing techniques i will scan my fsm 4 u the pages delaing with your diagnosing your hvac control head.
Mike

ke4mns

i just got the car on tues i will get a fsm,just want to deal with this while every body will be out of our shop and i can work on it,just needed some ideas so i could start trouble shooting tom.
Mark

NebCorvette94

Think your outside temp sensor is disconnected or damaged, It should be, right side of engine, top right corner of radiator. You can check it with a multi meter.


http://forums.corvetteforum.com/c4-g...o-the-rad.html

mtwoolford

In the past, many members with similiar issues have found the little heater / A/C control module, mounted on the inside of the firewall above the gas pedal to be the source of their problems; it routes vacumn to the various heater and A/C functions and over time the small nipples that the various hoses mount onto soften and deform (amongst other problems) leading to loss of function and / or erratic operation.

While it is never wrong to ask a question, I cannot over state the value of the search function on this forum; rather than expecting members to reinvent the wheel with each new thread, the problem (whatever it may be) almost certainly has been addressed multiple times before, often by very knowledgeable people who, besides discussing the issue in depth, also posted pictures and schematics.

ke4mns

well i did search but nothing really doin what mines is doin,ok see if ya guys agree with my synopsis.If my outside air is feeding the control module a reading of 50-60 degrees if i turn it to 60 to kick it on it wont because its thinks its satisfied and wont turn the ac on would i be correct in my thinking
Mark

CorvetteMike2024

Here you go. Sorry it took so long. My house got flooded yesterday from the S. Cal rainstorms This is from my 89 FSM

ke4mns

thanks mike i found the outside air temp sensor is bad but still got to test it.one more stupid question what is the pump behind the driver seat in the trunk floor

CorvetteMike2024

That has to do with your anti lock brakes.

ke4mns

ok thanks,and thanks for all the help,ill order fsm after holidays merry xmas,ill put up some pics of my vette and harley when it warms up later mark