Testing the evaporator core

[Robert C.]

Guys,

The '67 I'm in the middle of right now supposedly had the evaporator core replaced when the major body-off work was done.

Heater core nipples look new. Evap I'm iffy on. That was just based on the appearance of the insulation, POA valve, Expansion valve.....

I sent out the POA abd expansion valve to Classic to get rebuilt.

I have a new condensor.

Question is testing the evap core without pulling it.

I installed vacuum caps on the small refrig line coming off the POA valve and the lower line to the evap core. I oiled both lines with refrig. oil to get a good seal.

I then slipped a piece of oiled 3/4 heater hose over the top evap lines, inserted another hose and clamped everything together. It's been holding about 20 inches of vacuum for an hour, but I realize this test is a bit
jury-rigged.

Any acceptable way of testing on the car? I heard shops test with nitrogen at 150 psi somewhere, but that assumes you can bring the part in.

I followed the same process with the condeser and it held for over 2 hours just fine.

Evap wouldn't hold at 22 inches of vacuum, but it hit 20 inches and seems to be holding steady.

Any opinions? What have you guys done?

Bob

[Tom K.]

Re: Testing the evaporator core

Bob, I'm not an A/C expert, but the first thing that I do after having a system open is to pull a vaccumn for about an hour and then wait at least another hour to see if it will hold. I think you are on the right track. The other option would be to rent a tank of nitrogen and pressurize the evaporator. But I'm not sure how you would check for leaks without pulling it out. Maybe someone with more experience can offer other suggestions.
Tom
.

[Robert C.]

Re: Testing the evaporator core

Thanks Tom......good point about buying a small tank of nitrogen.

I'm going to start nosing around for AC tools, might be able to pick something up.

Overnight, I went from 20 inches down to 5 inches, but this was with push on seals & hoses.

Bob

[Joe R.]

Re: Testing the evaporator core

Hi Robert:

I'd be careful testing the evaporator at 150 psi. I believe the normal operating pressure for the evaporator is fairly low, like 30 psi or less. It is the lowest pressure point in the system.