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Any A/C experts?

Master Hack

Master Hack

fixin to break it
Donator
Don't know if this is the right place to ask but it's engine ish. Classic Auto Air started blowing warm. Was fine on Thursday, hot wind on Friday. Already disabled the sketchy electric water valve with a 1/2 full port ball valve, so I know that's off.
Fan blows and compressor still engages the pulley so as I understand that means there is still adequate refrigerant yes? According to CAA website the high/low pressure switch will not allow the compressor to engage if too little or too much refrigerant, so that has me thinking it can't be a leak problem. The website troubleshoot just says if the compressor kicks on, check water valve, and I know that's not it. Any ideas?
 
I suggest getting a set of gauges to see your low and high pressures.

I have Classic Auto Air under dash unit daily driver with a serpentine 508 Sanden compressor.

The ‘65 sits in a non-heated garage during winter…darn cold sometimes too.

The a/c was not working optimally back in April, but I did not have time to mess with it before a road trip to Colorado.

Apparently, I must have lost a minor amount of refrigerant due to extreme cold weather. Did not find any leaks last week while troubleshooting.

My compressor did engage and tried to cool, however there wasn’t enough refrigerant in the system according to the high pressure side gauge…like barely making high pressure.

Used old reference pictures when I did initial 2021 (May).

I did not want to just add more without information to guide me to do so.

I also checked the binary switch and wiring behind the grill too, no issues.

Hope this helps.

Low side ~ 25-50 on R134a scale.
High side ~ 82-100 on R134a scale.
RH center vent = 40F

Expert by no means.
IMG_0885.jpeg

Found this chart online today.

IMG_1093.jpeg
 
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As suggested, get yourself a set of gauges.
It is probably low on refrigerant. It can be a little low and still have enough to trip the pressure switch so it will run, but not enough refrigerant to adequately cool.
If you were closer, I would say bring it over, as I have everything here.
 
Thanks I may just get some gauges and learn how to use them. I may come back after Amazon delivers them this afternoon HA! Any particular brand recommendation? I have an a/c tech buddy who owes me a favor (or 10) because I gave him my 289 for his Falcon project, but the bastid is not answering my text.
 
Master Hack said:
Thanks I may just get some gauges and learn how to use them. I may come back after Amazon delivers them this afternoon HA! Any particular brand recommendation? I have an a/c tech buddy who owes me a favor (or 10) because I gave him my 289 for his Falcon project, but the bastid is not answering my text.
Click to expand...
You can buy refrigent at a parts house with a gauge on it . They work pretty good if your just correcting the charge .
Even if you purchase a set of automotive gauges you might have a problem with a cylinder of refrigerant to use .
 
134 at 72* should be close to 74 lbs with the system off. Off is let it set long enough for everything to stabilize pressure and temp.
At this point both high and low side should read the same. again system off and stabilized.
from my pressure temp chart
76=80
80=86
84=93
88=100
92=108
r12 pressures are slightly lower 1234yf slightly higher
 
Went to Harbor Freight and got something for the new tool thread. Decided not to get the cheapest one. I try not to buy the cheapest anything, it never seems to work out well. The directions say diagnostic with the car at temp, A/C on?
You say I can hook up the gauges with the car off and read static pressure first?
 
Master Hack said:
Went to Harbor Freight and got something for the new tool thread. Decided not to get the cheapest one. I try not to buy the cheapest anything, it never seems to work out well. The directions say diagnostic with the car at temp, A/C on?
You say I can hook up the gauges with the car off and read static pressure first?
Click to expand...
Static pressure will tell you if it is full to the correct amount or over full.
running tells you how the system is working.
you cannot tell how it is working if it is over or under filled
 
I hook up gauges and get static read first. That may tell you enough. Then when you start it watch the pressures.
Freon is a weird chemical. You can look at the pressure, and a chart, and tell exactly the temperature. But if there is not enough Freon in the system, it can not remove enough heat to help.
 
So your're saying with my garage at 92 degrees (probably is) my LOW side should read 108? With the motor off and my garage 90+ they read about 15 psi each
 
Yeah, I think the compressor switch cuts out below 30 or 35 lbs. Remember what I said about pressure and temperature? They set it so low side will not drop below 35 or 38 degrees so evaporator doesn’t freeze up.
 
Master Hack said:
Verified volt to the compressor 1.6 CAA troubleshoot says Low side pressure should be 10-25 psi?
Click to expand...
do you have a vacuum pump
at this point rather put more in either suck it down for 30 min and see if it will hold a vacuum.
for a couple of hours. If it doesnt i made an adaptor to put compressed air in the system and see if you can find the leak that way.
you can put in over 100psi will not hurt anything. If i had nitrogen i would use that but i dont and shop air works as long as it is dry.
 
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