AC Compressor Test?
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Cross-Country
Joined: Feb 2021
Posts: 95
Likes: 7
AC Compressor Test?
Welp, a 16 year old pulled out in front of me Saturday night. Luckily we are all OK.
The Mazda B truck still drives but it'll need some body work before it can go back to being my daily.
In the mean time I will be driving my 88' F250.
It's been in the 90s and near 100% humidity in good ole East TN, so I want to fix my A/C in the truck. I'm sweating like a dog out here!!
Here's what I got:
Its been R134a converted.
I replaced the valves, and charged the system, but can't get the compressor to kick on. Odd note--The system read 0psi when I plugged in my gage, and quickly charged up to 40psi with not much refrigerant at all.
I can rotate the compressor by hand. As far as I can tell, it's not seized.
I have no blown fuses, and the connector is securely fastened.
The "AC" button on my center console lights up and is operational.
Is there any "force on" test I can do with the compressor? Or do I need to pull it and take it to get tested?
I have little to no experience working on AC systems. So, any help is much appreciated!
The Mazda B truck still drives but it'll need some body work before it can go back to being my daily.
In the mean time I will be driving my 88' F250.
It's been in the 90s and near 100% humidity in good ole East TN, so I want to fix my A/C in the truck. I'm sweating like a dog out here!!
Here's what I got:
Its been R134a converted.
I replaced the valves, and charged the system, but can't get the compressor to kick on. Odd note--The system read 0psi when I plugged in my gage, and quickly charged up to 40psi with not much refrigerant at all.
I can rotate the compressor by hand. As far as I can tell, it's not seized.
I have no blown fuses, and the connector is securely fastened.
The "AC" button on my center console lights up and is operational.
Is there any "force on" test I can do with the compressor? Or do I need to pull it and take it to get tested?
I have little to no experience working on AC systems. So, any help is much appreciated!
Lead Driver
Joined: Feb 2002
Posts: 7,966
Likes: 595
From: Greater Austin, Texas
There is a switch on the accumulator that will not allow the compressor to come on if the charge is low. You could jump it to make the compressor run, but it sounds like you don't have much refrigerant in the system. If you have 40 psi sitting still with the compressor not running, that is almost nothing.
Thread Starter
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Cross-Country
Joined: Feb 2021
Posts: 95
Likes: 7
There is a switch on the accumulator that will not allow the compressor to come on if the charge is low. You could jump it to make the compressor run, but it sounds like you don't have much refrigerant in the system. If you have 40 psi sitting still with the compressor not running, that is almost nothing.
I had a leak at the high-side valve. So, I assume the system is practically empty.
Cargo Master
Joined: Nov 2009
Posts: 2,190
Likes: 620
I can almost guarantee you'll need to jumper the switch for the first part of your fill. I've never had one of these trucks that would get the compressor running on it's own, from a freshly evacuated state. My method is typically to hook up my gauges, and get the first can flowing, and then manually bump the compressor on and off with the jumper wire. In my experience, once you get the first full small can of R134a (I always seem to end up with the smaller cans, for whatever reason), you can generally hook the pressure switch back up, and fill normally.
Lead Driver
Joined: Feb 2002
Posts: 7,966
Likes: 595
From: Greater Austin, Texas
I can almost guarantee you'll need to jumper the switch for the first part of your fill. I've never had one of these trucks that would get the compressor running on it's own, from a freshly evacuated state. My method is typically to hook up my gauges, and get the first can flowing, and then manually bump the compressor on and off with the jumper wire. In my experience, once you get the first full small can of R134a (I always seem to end up with the smaller cans, for whatever reason), you can generally hook the pressure switch back up, and fill normally.
You can avoid this if you will put the 1st can in thru the high side after your vacuum step without the truck running. This will "preload" some refrigerant in so that, when you start up the truck and turn on the a/c, the compressor will engage. It may cycle until you get the 2nd can in.
Cargo Master
Joined: Nov 2009
Posts: 2,190
Likes: 620
You can avoid this if you will put the 1st can in thru the high side after your vacuum step without the truck running. This will "preload" some refrigerant in so that, when you start up the truck and turn on the a/c, the compressor will engage. It may cycle until you get the 2nd can in.
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Hotshot
Joined: Jun 2015
Posts: 12,871
Likes: 2,445
Maybe I’ve been lucky but with a good vacuum on the system it should pull enough into the system to trigger the low pressure cycling switch.
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Cargo Master
Joined: Nov 2009
Posts: 2,190
Likes: 620
Thread Starter
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Cross-Country
Joined: Feb 2021
Posts: 95
Likes: 7
Worst case I wasted $20 in refrigerant. I'm pretty sure I found the leak at the high side Schrader valve.
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