I'll try to make this quick.

I have a 1990 coupe with lt4 hot cam, TPIS headers, and the rest. I'm in Florida, so I need the coldest air conditioning possible. I have c68 a/c.

My a/c in the evaporator box is 38 degrees, system pressures are good with a/c gauges (30 low side, 200 high side) using enviro-safe refrigerant, air flow (blower) is good. Programmer appears to be working well, and the control panel works correctly also. No codes at all on the control panel.

I recently replaced the heater core, with a 1996 blend door motor (on the bottom instead of the top and a perfect fit by the way) and the center vent temp is 60 degrees (marginal) on recirculate, max air.

I've checked for leaks anywhere, sealed the evap box. recirc door operation is working correctly, its all apart but working. I've bypassed the heater core for diagnostics of the blend door, but no change.

The question is this. Where can warm air be getting in from the evap box to the vents. 38 to 60 degrees is a big jump in temps!

I'm starting to wonder if the headers are warming the evap box air beacuse I can't find anything else.

Anybody else ever have this issue?

 

How much air flow might just need to clean the coils would not hurt to put a shield for the headers

 

Forgot to mention, new evaporator, new condenser, new compressor, new orifice tube all flushed and spotless. Wrapped the lines with insulation too.

Might try to wrap the (ceramic coated) headers next. Just getting really frustrated with this.

Thought maybe a pro a/c person might have run into this before. I ripped the car apart and really thought this would be a more obvious problem.

Thanks.

 

Is your blend door working correctly? Assuming you disconnected the battery while doing the work, the HVAC system should have recalibrated it the first time it was powered up.

To check the blend door, remove the blower control module from the evaporator housing and set the HVAC control panel to 60°. The blend door should be in this position:



Set the HVAC control panel to 90°. The blend door should be in this position:

 

Blend door works perfectly, also bypassed the heater core...just for diagnosis.

I really had to check this, as I switched the blend door actuator from the top (1990) to the bottom (from a 1996). seem to work great, by the way.

But.....i'll check it's operation again.....

Thanks Cliff. I'm really at a loss here..

 

I'm no expert at this but I'd 100% plug the outlets and with the fan on slow look for cold air.

Maybe do a smoke test as is done w/an intake leak?

 

Hope you find the problem, no A/C is Florida is brutal.

Rick

 

The header wrap will make the ceramic coating come off. Been here done this.

Try to do a heat shield over the box. there is really not a lot there to block engine heat. Actually nothing. My combo cracked my brake booster open. I made sure my replacement was metal. That is a bit further from the clearance on the passenger side of the car.
Also had my starter give out on me, and I had to heat shield it as well.
I also had to heat shield my fuel pressure sender on me fuel rail.

when I pulled my engine and trans out, I put heat shielding in the trans tunnel. I felt like that made a decent difference, but who really knows.

 

I finally figured it out. Geeeeez.....What a nightmare...

After ripping the whole thing apart and checking everything,...I finally noticed there was a 1" gap between the firewall and the evaporator. The seal was not put in. I guess this allows warm air from the heater side to enter the box. Pulled out the resistor and jammed some insulation foam in there and now its COOOOL!!!!

From to in 15 minutes!!