Need help on heater and ac problems
Thread Starter
Burning Brakes
Joined: May 2005
Posts: 1,247
Likes: 1
From: SHREVEPORT LA
Need help on heater and ac problems
Heater wouldn't warm up this morning, but then tried ac and cold air comes out underneath and through the defroster vent, not through main vents, switches cycle, lights change, fan changes speeds, can hear compressor come on and off, but no warm air on heat and ac comes out of the bottom 
Any ideas? TIA
Any ideas? TIA
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Air only through the defroster and heater is generally a vacuum problem. I don't know the source location on the ZR1, but follow the vacuum diagram labeled HVAC. It will pass through a check valve near the firewall. One side will tee off and go to cruise and the vacuum tank; the other side goes through the firewall to the rear of the Programmer. Check valve is often the culprit.
No heat can be a plugged core or a temp door that fails to move - sometimes because the plastic link connecting it to the motor that operates it has broken. To observe the door, remove the Blower Control Module on the left side of the Evaporator Case and look inside. Door should move as the controls are cycled between 60 and 90. Access to the linkage and motor are from the passenger's compartment. Remove the hush panel.
If vacuum is good and the door linkage is intact, best to troubleshoot the system with a Tech 1. It will mimic the control panel through the CCM connection and if it all works, the control panel is faulty or there is an open in the serial data line. If it doesn't work, the Programmer is bad.
No heat can be a plugged core or a temp door that fails to move - sometimes because the plastic link connecting it to the motor that operates it has broken. To observe the door, remove the Blower Control Module on the left side of the Evaporator Case and look inside. Door should move as the controls are cycled between 60 and 90. Access to the linkage and motor are from the passenger's compartment. Remove the hush panel.
If vacuum is good and the door linkage is intact, best to troubleshoot the system with a Tech 1. It will mimic the control panel through the CCM connection and if it all works, the control panel is faulty or there is an open in the serial data line. If it doesn't work, the Programmer is bad.
Thread Starter
Burning Brakes
Joined: May 2005
Posts: 1,247
Likes: 1
From: SHREVEPORT LA
I have been told there is no vaccuum on my system since it is the auto climate model. Does this mean it is the programmer probably? Are they expensive or could there be other modules that could be causing this since it is electronic? Thanks for any help.
Advanced
Joined: Mar 2003
Posts: 60
Likes: 0
From: Honolulu HI
I don't know if your a/c system is the same as my '96 auto a/c system, but the problem you described is the default condition on my vette when there is no vacuum to the programmer. The vacuum feeder line is on the passenger side of engine. This vacuum line goes into the passenger compartment and is connected to a fitting that connects to the programmer (above the gas/brake pedals). The solution to my problem was a bad connection between the connector and the programmer. I just played with the connection with the a/c on with the engine running (needed to get a vacuum) and when I made a good connection the air came out of the main vents. Another possible cause for a vacuum leak at the programmer is the rubber nipples on the programmer could be cracked and leaking. I also found this problem when I took the programmer out to inspect it. I hope this helps.
Advanced
Joined: Feb 2004
Posts: 72
Likes: 0
From: Huntsville Alabama
Originally Posted by dbriana
Heater wouldn't warm up this morning, but then tried ac and cold air comes out underneath and through the defroster vent, not through main vents, switches cycle, lights change, fan changes speeds, can hear compressor come on and off, but no warm air on heat and ac comes out of the bottom Any ideas? TIA
Any ideas? TIA
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Just to clarify - Electronic Air does rely on vacuum to move the heater, vent, defroster and outside air doors. The Programmer switches ports based on inputs from the Control panel. The temperature door, which determines heat or a/c or a mix of the two, is controlled by an electric motor. It's movement is also controlled by the Programmer based on Control Panel settings and inputs from outside and inside temp sensors.
