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40th Anniversary Want heat, but AC seems to be on all of the time. Plus temp gauge not working?

1993 40th Anniversary Corvette Topic

silverstreek

Member
Joined
Dec 8, 2015
Messages
7
Location
Huntingtown
Corvette
1993 Anniversary edition, Red
A recently purchased 93 Corvette has a few issues I've been trying to resolve. One issue is when turning the heat on, I've noticed cold air blowing. I've also noticed the AC compressor is running. I did disconnect the compressor to see if this was the case where the AC was over-riding the demand for heat. I also checked the heater hoses to make sure I had flow, and to also make sure there were no blockages. They both seem to be hot, but still no heat coming from the floor, defroster, or vent duct work. I'm wondering if anyone has run into this problem before?

I also have an issue with the coolant temperature gauge not working. The signal to the instrument cluster showing the coolant temperature in degrees works fine. While researching this I did read where some of the earlier coolant temperature sending units were defective after a while because they leaked internally causing a gauge malfunction. Has anyone heard of this before?

What I don't want to do is throw parts at any of these problems. That gets expensive, and sometimes you don't know what the original problem was, or why it happened in the first place.


Any help or suggestions would be greatly appreciated!
Silverstreek ;)
 

VETTETECH

Member
Joined
Dec 2, 2015
Messages
24
Location
Chantilly, VA.
Corvette
1987 base
A recently purchased 93 Corvette has a few issues I've been trying to resolve. One issue is when turning the heat on, I've noticed cold air blowing. I've also noticed the AC compressor is running. I did disconnect the compressor to see if this was the case where the AC was over-riding the demand for heat. I also checked the heater hoses to make sure I had flow, and to also make sure there were no blockages. They both seem to be hot, but still no heat coming from the floor, defroster, or vent duct work. I'm wondering if anyone has run into this problem before?

I also have an issue with the coolant temperature gauge not working. The signal to the instrument cluster showing the coolant temperature in degrees works fine. While researching this I did read where some of the earlier coolant temperature sending units were defective after a while because they leaked internally causing a gauge malfunction. Has anyone heard of this before?

What I don't want to do is throw parts at any of these problems. That gets expensive, and sometimes you don't know what the original problem was, or why it happened in the first place.


Any help or suggestions would be greatly appreciated!
Silverstreek ;)

Most likely the temperature door control motor is inoperative OR the linkage from the door to the motor has disconnected...Not an easy repair..Requires interior and exterior HVAC box removal....Not for the novice to tackle..
 

silverstreek

Member
Joined
Dec 8, 2015
Messages
7
Location
Huntingtown
Corvette
1993 Anniversary edition, Red
Most likely the temperature door control motor is inoperative OR the linkage from the door to the motor has disconnected...Not an easy repair..Requires interior and exterior HVAC box removal....Not for the novice to tackle..

Unfortunately I've tackled a few of these repairs on different vehicles having to remove the HVAC box attached to the firewall. I know they're not for the faint of heart.:ugh It seems GM and many other manufacturers must believe their suppliers based on the lowest bids don't believe their parts will ever go bad in such an inaccessible area? If that ain't a joke! I would venture to say if these engineers who designed and wedged some of these pieces and parts into areas only someone who was a HUMAN PRETZEL could access. I'd say if they had to repair their own vehicles? Things would quickly change for the better, and they'd make the lives of those who turn wrenches for a living that much easier! Apparently that's too easy......

Right now I'm am in the process of getting the GM Corvette manuals I've recently ordered. I want to see what troubleshooting ideas they have trying those first. Being an optimist, I hope this fix is something simple? THIS TIME :chuckle


I appreciate your suggestions and will keep you informed once I start getting into this little problem.
Thanks again!

Silverstreek
 

Nojamin54

New member
Joined
Jul 27, 2016
Messages
1
Location
Hollywood, Florida
Corvette
1993 40th Anniversary
Box at Firewall

I could not agree more about the engineering staff working on their own cars!
Here's my dilemma;
On my 1993 40th Anniversary the HVAC head unit was a pretty straight forward removal and now I have the program box off the firewall and would like to know if there is a way to remove the vacuum block and power plug from the unit before I go yanking on the 23 year old vacuum lines.
I'm 62 years old, 6'0" and over 200 lbs. wedging myself under the dash isn't as easy as it used to be, any hints would be greatly appreciated.

Nojamin
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
I could not agree more about the engineering staff working on their own cars!
Here's my dilemma;
On my 1993 40th Anniversary the HVAC head unit was a pretty straight forward removal and now I have the program box off the firewall and would like to know if there is a way to remove the vacuum block and power plug from the unit before I go yanking on the 23 year old vacuum lines.
I'm 62 years old, 6'0" and over 200 lbs. wedging myself under the dash isn't as easy as it used to be, any hints would be greatly appreciated.

Nojamin

Very rare for a 93 HVAC programmer to cause a problem.
If the air is coming from the wrong vents the vacuum check valve is usually the problem.
Does the cruise control work? It shares the same vacuum source as the HVAC programmer.

Remove the passenger side fuel rail cover. You should see a valve this?
Input is the vacuum source and there are two outputs from the valve.
One goes to the cruise control black plastic round Vacuum reservoir.
The other hose to the HVAC programmer.

 

DonB

Well-known member
Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
I could not agree more about the engineering staff working on their own cars!
Here's my dilemma;
On my 1993 40th Anniversary the HVAC head unit was a pretty straight forward removal and now I have the program box off the firewall and would like to know if there is a way to remove the vacuum block and power plug from the unit before I go yanking on the 23 year old vacuum lines.
I'm 62 years old, 6'0" and over 200 lbs. wedging myself under the dash isn't as easy as it used to be, any hints would be greatly appreciated.

Nojamin

Nojamin, I couldn't agree with you more about the engineers getting their A$$es under there. I'm also 62 years young and 5'10, 210 myself. I get a neck-ache just thinking about it. I had my whole dash apart last year tracing a short. Even though it takes a bit more time, I remove the seat(s) first. It's also easier(I found) if you have the car up on stands too.
 

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