C4 AC / heat airflow problem

[Jim S.]

[Ed N.]

Re: C4 AC / heat airflow problem

Jim, I checked the factory service book and It may not be that bad to trouble shoot. It will come down to a few issues:

1. A restriction in a vacuum line to air door actuator

2. A defective air door actuator

3. A binding air door or linkage

I think you have my number. It's best if you call be because there is a lot to discuss. According to the book, the you need to remove the lower LH trim from the instrument panel in order to perform a vacuum actuator test.

[Joe L.]

Re: C4 AC / heat airflow problem

The ’96 convertible did well at Old Town last month and I’mlooking forward to the SE Regional in Bowling Green in April where I’mregistered for PV. The problem is the “actuator”which directs air in the AC/heating system is not functioning correctly. I did lose my first points in operations whenit balked at moving from the footwell, to the dash outlets, and to thedefrost position. At times it seems notto move at all and other times it is just very slow. I know this will be a failure in PV and needto do something about it before we make the trip. This is a very low mileage car and has hadtimes when it sat for more than it should – maybe it just needs to be exercisedmore? The local dealer took a look andis not sure what the problem is and does not really want to tear out the dashto locate the problem and has an additional concern regarding finding partsonce he figures out what is not working right. Long way around saying HELP! Anysuggestions, ideas, or similar experiences you are willing to share will beappreciated.

Jim------


My guess is that it's one of the vacuum actuators. Unfortunately, all of the vacuum actuators in the system are GM-discontinued. I do not know if aftermarket replacements are available.

[Keith B.]

Re: C4 AC / heat airflow problem

Isn't there a vacumn control valve on the intake that controls vacuum flow to the HAVC system that is known to fail on LT1 with the electronic controls

[Joe L.]

Re: C4 AC / heat airflow problem

Isn't there a vacumn control valve on the intake that controls vacuum flow to the HAVC system that is known to fail on LT1 with the electronic controls

Keith-----


The only valve in the system I know of is the one currently known as GM #15733271.

[Ken A.]

Re: C4 AC / heat airflow problem

Jim,
The dash programmer is connected to a module that uses solenoids to control the vacuum ports. On a 96 the hose connection was changed to a rubbery plastic that breaks down over time and blocks the ports. Remove the manifold from the module and clean out the lines & ports.

[Jim T.]

Re: C4 AC / heat airflow problem

Interesting post for me. About two years ago my seldom driven original owner 96 LT4 started an air conditioning air flow problem. I always use MAX air when air conditioning is needed. The problem when the 96 is taken out of the garage after sitting for months the dash vents do not distrubute the cold air conditioning when selected. My 96 has the electronic optional system. The defroster and floor outlets supply the cold air conditioning on startup even though MAX air is selected. After being driven for about say 10 minutes this changes and cold air conditioning stops coming out the defroster duct and floor ducts and correctly flows from the dash vents. I have had my 96's Corvette service manual since the 96 was new and have read the air conditioning section, but have not tried to do any testing since the problem has always corrected.

I have wondered if disconnecting my battery and having no electrical supplied to the car for months could contribute to the problem. When the car is not being used the battery has always been disconnected for months and air conditioning always worked correctly until couple years ago.

[Ed N.]

Re: C4 AC / heat airflow problem

Jim,
The dash programmer is connected to a module that uses solenoids to control the vacuum ports. On a 96 the hose connection was changed to a rubbery plastic that breaks down over time and blocks the ports. Remove the manifold from the module and clean out the lines & ports.

Ken, by manifold, do you mean what plugs into the programmer under the dash?

[Ed N.]

Re: C4 AC / heat airflow problem

Jim, these electronic control systems tend to be inconsistent, They typically work when they want to work. Keeping the battery connected and charged always helps.

[Ken A.]

Re: C4 AC / heat airflow problem

Yes, that's usually 90% of the problem on a 96.

[Cathy S.]

Re: C4 AC / heat airflow problem

Same symptoms here. Mine needed a new controller.

[Joe L.]

Re: C4 AC / heat airflow problem

Same symptoms here. Mine needed a new controller.

Cathy------


Yes, the controller is another strong possibility. These things seem to go "berserk" with some regularity. I didn't want to suggest the controller because it's GM-discontinued and expensive. For just this reason, I bought several of these controllers for my 1992 before GM discontinued them [none for sale]. However, the controllers can be repaired by folks that specialize in ECM and other controller repair.