A/C questions

[kjhansen]

Any A/C experts out there? I'm running Duracool in my '87 TR and it works great... except it quit working. When I jump the low pressure switch and manually start the compressor, it blows very cold. Could this be a bad switch? Can I replace this without letting all the refrigerant out? Oh, and btw, what should the low-side pressure be? Thanks.
Keith

 

[Nick Micale]

If you are talking about the switch on the dryer, it should have a shrader valve to keep pressure in the system.

In a good system, the compressor should pump down to 25 psi.

 

[kjhansen]

Nick,
Thanks for the prompt reply! I should have guessed it would be you--you've answered many of my questions in the past. Anyway, is the dryer the round canister next to the firewall where you attach the hose when you recharge the system? What I know about AC is limited you might say. I measure the pressure on the low side there, where I would hook up the hose if I were recharging. I have a guage that's just like a tire gauge in shape and function, but it's marked for AC and has the bigger end to fit on the schrader valve. It's a "Sercon A/C check gauge." Its "low side" markings go from 5 to 101.

It's got two "bar graphs" on it--one for low, one for high.

It says for low that 23 to 43 psi is "normal," 43 to 65, is "caution," and 65-200 is "danger." That pretty much matches up with what you said, i.e., the low side being as low as 25.

High side has 0-55 as "low," 55-86 as "normal," 86-101 as "caution," and 101-200 as "danger." Are these about right?

But when do I measure? With the compressor running or not running?

Plus, are you saying that there's another schrader valve on the dryer, i.e., one UNDER the low pressure switch (the switch that turns the compressor off if the low-side pressure is too low)?
Thanks.
Keith

 

[dgreene]

Keith,
The low side numbers are about right. Those high side #'s you posted would only be right if the system wasn't running. Any auto AC system the I have serviced wouldn't blow cold till the high side is up around 210 or so. Now that's talking about a 95 degree day though, on a cooler day the high side preasure would be lower. Anyway, lets say if you were working on it and it's 90 outside, the low side should be around 25-30 and the high around 210 or so. I have spiked one to 300 before but that is just asking for a line to blow or the compressor to lock.

Back to your original question, yes it sounds like your low preasure switch has bit the dust and yes there is a valve under it that permits it's removal and replacement at anytime without losing refidgerant.