HVAC problems

Hey I have a 95 Riviera SC that has no heat and no a/c. The interior air temp sensor is working and the blower is working and the car is able to control which vents it blows to and changes speeds everything acts normal. However it only blows air that's it. Cold in the winter hot in the summer. Any ideas why?

Could be a lot of things! Start with the basics. You may indeed have two separate issues.

Sounds like your heater core could be plugged. What shape is your coolant in? If it's brown and muddy (or was) the heater core could be blocked. When the engine is warmed up, do the heater hoses feel hot? Both of them? Low coolant will also do this.

For the A/C - is the compressor running? Are the lines getting cold?

There is also an actuator controlling a blend door. If you change from cold to hot on the HVAC head, is there any change? Can you hear the blend door move? (you can usually hear something move - turn the fan to low)

I have not heard the compressor turn on at all. I do not have any issues with the heater core just got done rebuilding the engine and trans all fluids are new and fresh including the freon in the a/c. I am not certain about the blend door. I don't hear anything when switching from heating to cooling so that very well may be it. The rest of the actuators on the vehicle have had to be replaced as well. Do you know where I could find one of these actuators?

The actuators are all over junkyards and such - a very common GM part. car-part.com has them, if you look up Ed Morad (a used 3800 specialist) his yard tends to have a number of them them in stock too. But you want to make sure that's actually the problem before you go after it.

If the AC compressor isn't running at all, it's probably lost the refrigerant charge. Usually that's from a leaking compressor seal, but again it's not always the case. There are other seals and o-rings, sometimes the condenser gets a hole in it, or anything else could cause the leak. Usually you have the system evacuated and recharged, along with a dye added so they can find the leak later. (don't wait too long for them to look for the dye) It could be very obvious where the leak is when they try to evacuate the system and put a vacuum on it.

Thanks for the help I'll check the actuators and I'll double check the pressure. I have some of the dye for checking lines already so if I have lost the pressure that is next on the list!

Also be aware that the actuators have a plastic gear inside which is prone to breakage. Make sure the replacement is tested and has some kind of guarantee. There are nearly as many broken ones as good ones out there!

JBDA1337 wrote:

Thanks for the help I'll check the actuators and I'll double check the pressure.  I have some of the dye for checking lines already so if I have lost the pressure that is next on the list!

I read the thread. the FIRST place I'd look is at the refrigerant charge. You will need a manifold set and a vac to evac and refill the AC. And don't EVER use the refrigerant with additives on this car with its radial compressor, you will eventually be sorry. very sorry.

Albertj

Problem with HVAC module?
I recently needed a new AC compressor. Had it installed, worked fine for a few days, but then didn't produce cold.
I took it back to the shop. They showed me how they could turn on the system using a remote diagnostic pad of some sort and said the AUTO button wasn't triggering the compressor.

Anyone know the fix? Replace the whole control unit? Or can that button go bad?

I also recently installed a new alternator (rebuilt) from Rock Auto. Turns out the shop discovered it is only putting out at 33%.
Could that affect the AC system?

To answer my own question, yes, the HVAC control box had a problem sending a signal to start the compressor.
Replaced through an eBay vendor. All good now.

Hm, the Auto button itself doesn't trigger the compressor, A/C can work both in Auto and manual modes.
Anyway, glad you fixed your problem.

The diagnostician gave me that, but I believe you
Thanks.