-=Jeff=-

I knew the compressor was smaller, but did not know how much smaller it was.. Also having a black car does not help either.

-=Jeff=-

I think I found another potential problem.

There are 2 vacuum doors for the floor vents ( front and rear) when in Recirc or AC, they both should be closed. When I was checking some things yesterday I noticed cool air through the floor in AC mode (vents only). It seems like one of the floor vents is not moving. I need to troubleshoot it more in depth but have a feeling the one door is not closing when it should, this would help with the volume of air through the vents.. due to the one floor door being open..

ddahlgren

It is 25 years old no matter how few miles it my have. I have this theory that like there are dog years there are car years and to me 3 to 1 seems right. So your asking a 75 year old to work like new on a 88 degree day. I know if I had to pull the whole heater box apart there would be a new heater core going in LOL. FWIW my 91 works better in recirc mode as it is not cooling air that is hot as outside air. I did the 134a conversion worst mistake I ever made don't even think it. The best I can get is 50 degree air.

Tom400CFI

Sorry but that theory is no good. It's not a living entity and "years" should only degrade rubber and foam. At any rate, it should all be diagnosable and chalking up poor performance to "age" is a sure way to never get it fixed. With well functioning parts, it should perform like new. OP is making head way w/the Blend doors.

-=Jeff=-

Yeah.. Hopefully I can get back to it this weekend

ddahlgren

Gaskets shrink hoses rot plastic cracks because it gets brittle moving parts wear bushings rot springs fatigue wire corrode the list is very long actually and this is just partial. The real problem is finding a replacement that fits properly and in new condition.

-=Jeff=-

Yes I am.. I am looking for ideas on what to look for.. I know the car is old, piece break and some need to be replaced..

It does not have to work like new, but has to be decent at best.. the system is good now I need to work on the flow.... I think if I find the root to the lower door, it might fix the issue I hav with volume from the blower

ddahlgren

There might be something to checking amp draw on blower motor though can't think of a good way to see if it comes fully up to speed. Would there be any benefit to connecting the heater core hoses together to get adding heat out of the loop? A ton of C4's have window tint as well to cut AC load. Simple question has it ever worked well while you have owned it? It was 90 here today with a bright sky and felt like an easy 98 with the high humidity. I let the thought of driving my 91 completely pass and drove the Pontiac. Tomorrow is supposed to be just as brutal.

-=Jeff=-

Yeah I thought of that too.. I replaced the blower a few years back. I am going to try again though (they are cheap enough)

I thought of this too, but I have decided against it, if I am going that route, I will install the valve like the older C4s have that bypasses it, but keeps everything connected

Yes I have mine tinted as well, but cannot go any darker since i decided to keep this car legal

Nope.. It had no refrigerant.. I have replaced several components and recharged r12

I drove my Malibu SS today for the same reasons

bill mcdonald

The vent issues sounds like a vacuum related failure.

I went though this on the C5. It would send air into a default setting. which was through all vents. This greatly reduced air flow.

I trouble shot this thing to hell and back. Build new vacuum hoses etc... turned out my AC controller was shot (electronic). replaced and everything worked. Never read about anyone having this issue. It was always vacuum line problems for everyone else...

I have a 90 as well, and the system IMHo sucks!

I replaced the ac controller, the fan motor, and cracked open the box and cleaned the inside out. there was nothing in there. There was a screen on it and I pulled that out hoping for more air flow.

It sucks so bad that I removed the AC. It was useless. It was actually in my way of working on the car.

My car is black, with black interior, and a modded engine. Thing did not work worth a damn.

If you can get the vents working, you will get better flow, but don't count on it being too good.

-=Jeff=-

I won't but IF I can get it working better at least out of the vents I am on the right track..

I also am tempted to add a heat shield on the Evap box on the motor side, I think that will help a bit too

ddahlgren

Assuming the air comes in at the base of the windshield does it work any better driving compared to sitting still? If you know anyone in the HVAC most all have a pressure probe used to balance ductwork and most people that have a Corvette knows a few other people that do to. Maybe a comparison test to see if it really is flow related. The HVAC guy would know how to compare inlet to outlet and all that jazz. I do realize all of them could be just as bad as well.

If the flow compares and the outlet air is a reasonable temp could the heat load be greater than the system can deal with? Add insulation maybe to lower the load.

mtwoolford

just a question, is the air flow adequate when the HVAC is in the "heat" mode, but less in the "cool" mode? if so, your evaporator could be clogged with who knows what

mtwoolford

another thought; there's a speed control that sets down inside the air plenum accessible from the engine side; there could be an issue there preventing your fan from coming up to full speed; at least (on my 96), it's easy to get to

-=Jeff=-

No both are the same.. I am guessing it is the one door I have yet to look into and troubleshoot

Mine is very basic since I have C60.. but I did replace it

Cliff Harris

The air ALWAYS goes through the evaporator. The temperature blend door either lets it go straight through into the ducts or diverts the air through the heater core.

If you pull out the resistor module (C60) or blower control module (C68) from the evaporator housing, you will see this when the blend door is in the 90° (C68) or max heat (C60) position:



The evaporator is at the left edge of the picture and the heater core is between the evaporator and the rusty blend door. When the HVAC controls are set for 60° (C68) or max cool, the blend door covers the heater core:

mtwoolford

As they say, one picture is worth a thousand words; for what its worth, I just had the dash apart in my in ford pickup and the blend door blocked off the fan discharge through either the heater core or the evap, so thanks for the clarification.

-=Jeff=-

Another thing I think I might see if it is feasible to wrap the HVAC duct work in the dash

I know that should also improve some cooling.

another is to add a heat shield on the Evap box near the motor

desertmike1

Jeff, do I understand you correctly, that the floor discharge doors react differently under the same Command? if so this is a huge Clue, you need to look at the FSM for a Vacuum diagram of the HVAC system. This may be as simple as a Bad Dash Pod (Vacuum Motor) at one of the Discharge Doors..

-=Jeff=-

Right. I need to look at it.. but I don't want to tear the car too far apart..

Maybe this weekend