Yompkins

I'm getting a high pitched whistle coming from my evaporator box while driving with the A/C on.

Is this normal?

I have a 1985 toyota pickup dlx longbed 22r 4x4 that did not have ac from the factory.

I recently collected all of the components and installed AC. Got a used toyota evap box, and hard liquid lines. I bought new r134a compressor, condenser, evaporator core, drier, expansion valve and soft lines.

After installation and charging the system the first time the low pressure side was staying between 5 and -5 psi and no cool air. I assumed i had a plug or a bad expansion valve.

After disassembly I found what looks like remnants of one of the rubber vacuum plugs from the condeser used to keep vacuum during shipping stuck in the expansion valve.



I got a new expansion valve and and drier from o'rielly. I dumped the oil from the compressor, re-oiled with 60cc in compressor and 40cc in the drier. System held vacuum for multiple hours so I charged with around 750g of r134a.

Now the system works great. I'm getting temps in the 40's out of the vents even at almost 100 degrees outside.

The problem is that while driving when the compressor kicks on I hear a loud whistling sound constantly coming from the evaporator box.

Is this normal?

Some online searching indicates this may be a sign of plugged or stuck expansion valve. Does anyone else have a whistling noise coming from their evaporator box?

Any help would be appreciated!

Yompkins

Does anyone else's evaporator box make a whistling or whining noise while the A/C is running?