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!

 

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

 

I was able to tear everything back apart and found some dye around the expansion valve signaling a leak (the pag oil I used for the compressor had neon yellow dye). After reinstalling everything, flushing the evaporator and blowing out all lines, I drained and refilled the compressor, replaced the dryer, reassembled and charged the system.

Overall, the system still makes a hissing/whistling sound when its running. I don't know if this is normal. If anyone can report that their evaporator box makes noise while running, I may just leave it and put the dash back on. Otherwise I may rip it apart again and see if there are any leaks in the evap box.

Can anyone confirm or deny if their evap box make a hissing/whistling noise while running. I'd rather not break open the system and recharge again if I don't need to.

 

My '85 does not whistle or hiss. Good luck

 

Thanks Sourdough. My worry about the noise was compounded by the fact that my low pressure gauge was never getting above 20psi. (2000 rpm, 85degF, 40% humidity, A/C on max). After running the truck for a day and taking another measurement under the same conditions, now my low pressure reading is up between 28-32psi as I would expect. I'm not sure what changed but I'm gonna do one more test today and then put her back together.

 

DIY is a pain but cheap. Hang in there and enjoy your efforts. I replaced everything during conversion to 134a. Works but heat valve was frozen and loosened that up to make sure it was closed. Just ordered an idle up adjustment valve because mine doesn't do anything and don't be surprised if yours is dried out too. Toyota Part 88606-32010 will be upside down but work. Fred Hass Toyota $42.33 delivered

 

I'll have to check that out. I currently don't have any kind of an idle up valve as my truck didn't originally have a/c. Thanks!