92 Chevy AC trouble shooting.

KARNUT · September 25, 2019

I had my AC converted last year to 134 by a shop I trusted. It did well for a year. A year later it quit cooling. I expected that with the difference in Freon. I bought a can with a gauge. Hooked to low side jump the compressor filled to 40 psi. It took very little cooling well. I unplugged and replugged what I assumed was the low pressure switch. Pulled my jump wire. While driving a week later still cooling well it stopped. The low side reads 40. Jumping the compressor it cools the accumulator gets cold. Doing research it appears the high and low pressure switch are in the compressor. The switch near the accumulator according to auto zone parts list turns on the compressor. I thought originally that was a low pressure switch. I jump those wires it turn on the compressor. Right now I’m too stubborn to take it in. Im thinking that switch is bad. Thoughts?

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Mikebtte · September 25, 2019

If the freon leaked out it could have sucked in air or moisture and you are now running freon and air/water together. Air will not cool well in the system.

You would be best off evacuating the system and locating the leak. Recharge with freon and it should work.

KARNUT · September 25, 2019

It only got warm when the compressor quit cycling

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KARNUT · September 27, 2019

I did replace the switch by the accumulator and it worked. I’m a little worried even though the low side is a 40 ( single gauge can fill) the high side may be too high. I guessing the high pressure switch that’s in the compressor will deal with that. I’ll check that next time I’m at the shop. I’m surprised how cool it gets for a R-12 to 134 conversion.

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SnakeEyeSS · September 29, 2019

You don't need to go to a shop, many parts stores loan out the full guage set.

KARNUT · September 29, 2019

You don't need to go to a shop, many parts stores loan out the full guage set.

It would be my old shop.

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Donstar · September 29, 2019

1 hour ago, KARNUT said:

It would be my old shop.

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Maybe they'd give you a discount....

KARNUT · September 29, 2019

Maybe they'd give you a discount....[emoji16]

I’m still part owner. Actually it’s shops-offices. I’m just going to borrow the gauges. I’ve never needed to mess with ac much before. I didn’t realize there were three pressure switches. There’s also a relay under the glove box. I figured there’d be people on here who knew all this. It seems there’s more opinions here than actual knowledge. Thank goodness for the internet. And auto- lmc parts catalog.

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silveradosid · September 29, 2019

low pressure switch turns the compressor on and off if the pressure is to low. the high pressure switch is to turn off the compressor when the pressure is to high. the other pressure switch is to turn on electric fans if equipped. the relay at the glove box is for turning on the fan at low speed to circulate air through the evaporator to prevent it from freezing

KARNUT · September 29, 2019

low pressure switch turns the compressor on and off if the pressure is to low. the high pressure switch is to turn off the compressor when the pressure is to high. the other pressure switch is to turn on electric fans if equipped. the relay at the glove box is for turning on the fan at low speed to circulate air through the evaporator to prevent it from freezing

No electric fans on this truck. I originally thought it was a low pressure switch. I jump it and the compressor turned on. According to auto zone parts list the low and high pressure switches are in the back of the compressor. I replaced that switch it’s working very well. I can’t see the reason for that switch. Of course most parts list covered multiple years. To get a good view of the compressor I’d have to remove it. Could be there’s just a high pressure switch on it? As long as it’s working I’m good. Thanks for your reply.

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