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89 Coupe - No heat at all

braeburn22

Member
Joined
Nov 14, 2006
Messages
7
Location
Edinburgh, Scotland
Corvette
1989 Bright Red Coupe
:) Hi

I'm new to the forum and I hope somebody can help.

I have a problem with my 89 Coupe with electronic climate control.

No matter what setting I put on the controller I get very limited heat from the vents, I have used the diagnosic mode on the head unit and this indicated both the internal and external air temperature sensors were faulty, I have replaced both of these but it still blows cold what ever setting it is in.

I have confirmed that I am getting water flow in and out of the heater matrix and the matrix is not leaking.

The only remaining fault that is showing on the diagnosic is the potentiometer position is incorrect, I was wondering if it could be a vacuum fault, the controller was recently replaced with a new unit.

Any help would be greatly appreciated as it is starting to get a bit chilly here in Scotland

Thanks
 

Bobsvette

Well-known member
Joined
May 14, 2006
Messages
204
Location
Enfield, ct
Corvette
2019 Torch Red Grand Sport
I have never had to have it done on a chevy but two different fords that i used to own had the same problem your describing,I usually do alot of work on my cars myself but to get to that blend door you pretty much have to take the dash apart, I won't attempt that. also does the engine seem to be running.hotter? if so i have seen the impeller in the waterpump rot away just enough to really slow down circulation. there's a member that really could help you here at c.a.c. that would be c-4 c-5 specialist.Look him up in the member list and p.m. him
 

3dale1

Well-known member
Joined
Mar 12, 2005
Messages
158
Location
PA
Corvette
65 convertible L-76
Maybe the heater control valve? Worth an easy check to see if the plunger receives amd/or holds vacuum.
 

Corvette95

Well-known member
Joined
Feb 7, 2006
Messages
60
Location
Bham,Alabama
Corvette
89 Conv,another 89 Conv,96 coupe,95 coupe,95 ZR1,
here you go, put the ac on 75. warm the motor up to operating temp. Look in the engine compartment near the firewall in FRONT of where the passenger sits, look on top of the outside heater box near windshield. There will be a plastic plate with a couple of electrical connectors on it. Take a 7mm socket and remove the three screws. gently seperate cover from heater box - may be stuck a little if never been off. After getting it off, take a flashlight and shine into the opening now, you will see the evaporator and heater core and blend door, WITH the motor RUNNING, have an asistant move the temp setting to 90 degrees, you should see the blend door move to one side of the heater box and seal off tightly, after that, have the assistant move the temp to 60 and see if the door opens and moves to the other side of the heater box and again seal off tightly, if the door DOESNT move, GENTLY take your hand or and long screwdriver and GENTLY break it free of stuck postition - only move it the direction it is trying to go to. Then fog up the door and BOTH side of the heater box lightly with WD40 - this fixes 90 percent of the time what you are describing - good luck!
Corvette95
 

braeburn22

Member
Joined
Nov 14, 2006
Messages
7
Location
Edinburgh, Scotland
Corvette
1989 Bright Red Coupe
we have heat again

Thanks to Corvette 95, I have heat again, the actuator is still inoperative but I have freed up the air mix door and moved it into the full heat position.

This will do for now until I can face dismantling the dashboard to get into the vacuum actuator
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,521
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
Thanks to Corvette 95, I have heat again, the actuator is still inoperative but I have freed up the air mix door and moved it into the full heat position.

This will do for now until I can face dismantling the dashboard to get into the vacuum actuator
Before you do anything check this check valve!!!! if it's Bad replace it!!! May be broken or the inside roted out of it,it's supposed to let vacuum flow only 1 way (from the engine)!!!If it's bad or broken this will cause the Problem you have!!! I hope you didn't break the Clip on the Actuator Rod of the air mix door!!!! If so you will still have to take the Dash top off,to replace the clip!!!!((And it's a REEEEL Pain in the Wazoo)) This Check Valve causes 90% of the Heat and A/C problems relating to vent and heat control!!!I replace them all first thing when I'm getting them ready to Resale!! It's less than $6.00 at the parts store!! It's under the Fuel Rail cover on passenger side!!:upthumbs

junk!!P.S. Oh Damn,I didn't notice you were in Scotland!!I don't know How Much or Where you can find one there!!
 

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