I need to recharge the AC on my tractor.

I bought a basic set of gauges and a couple cans of R134.

When I hooked the gauge up to the low pressure side, it showed 50+ pounds, actually in the red zone on the gauge. Question 1: What does that much pressure on the low side indicate?

I've had to have the system recharged every damn Spring since I bought the tractor. Obviously, I have a leak somewhere, and I've had o-rings replaced on the compressor (first year) and on the evaporator (2nd year). The system does seem to work well all Summer, but leaks down over the Winter. According to Dr. Youtube, a complete recharge is well within the skills of your average shade tree mechanic, IF you have the proper equipment, IE a full set of gauges and a vacuum pump. Given shop rates, I'm thinking being able to recharge the system myself makes sense financially. A kit is available on Amazon for $130.

So,

Question 2: Will pulling a vacuum on the system to dry it out also alleviate the overpressure on the low side?

Question 3: How do I know if I need to add oil when recharging?

Question 4: Is R134 with sealing additives a good idea or just snake oil and kicking the can down the road?

Question 5: What else do I not know that I don't know?

quote:

When I hooked the gauge up to the low pressure side, it showed 50+ pounds, actually in the red zone on the gauge. Question 1: What does that much pressure on the low side indicate?

Was this with the engine running and the AC compressor clutch engaged?
Normally with the vehicle not running, and both high side and low side gauges hooked up, the high side and low side pressures are the same.

It has been years since I have performed any automotive AC service but if I recall, 50 PSI static pressure is not too high for R134.

quote:

Originally posted by Patrick-SP2022:

quote:

When I hooked the gauge up to the low pressure side, it showed 50+ pounds, actually in the red zone on the gauge. Question 1: What does that much pressure on the low side indicate?

Was this with the engine running and the AC compressor clutch engaged?
Normally with the vehicle not running, and both high side and low side gauges hooked up, the high side and low side pressures are the same.

It has been years since I have performed any automotive AC service but if I recall, 50 PSI static pressure is not too high for R134.

Tractor running, AC on but compressor clutch not engaging. In the past, this has been because of low refrigerant. At one time I was able to disconnect the low pressure switch and force the compressor to run. I need to re-discover which connector is for the low pressure switch and try that and then re-check pressures.

I’m sure you’ll get better info but here’s my input. Evacuate the system, add UV dye and charge it up. Find your leak and repair that then evacuate and recharge. Don’t ever use sealants, it will cause problems when you have to fix it right.

#1 50PSI would be normal on a low charged non running system, was it operating or was the compressor off? The Low and High side should be in a vacuum (boiling out any moisture) with a pump attached to it.
#3 You add the same that you took out, drain the oil out of the component being replaced.
#4 Sealants are not good, check with parts department and ask them if a compressor warranty is valid if sealer is found in the system.
#5 Old timers don't like using safety glasses and gloves, use them anyway

Generally you need 40-50PSI to trip the low pressure and let the compressor run. Can you check the clutch trigger and see if it is getting the signal to turn on? You can't check pressures unless the compressor is running. With R134A low side should be around 30-50 and the high side is around 150. If the low side is too low, it may be low on freon or the orifice might be clogged.

If you end up evacuating, I would run the pump for about 40 minutes and close the valves. Make sure the vacuum doesn't change over 40+ minutes or you have a leak. Dye definitely helps find leaks. I let mine sit overnight before I was confident to fill it. Also charging by hand takes a long time. You should not tip the can upside down or you might damage your compressor. IIRC it took me about 30 minutes of running the motor to get the unit fully charged. Helps if you have a blow dryer to heat up the cans as they get cold.

Ah. All good info as usual on Sig Forum.

Raining today and no room in the garage so I'll follow all this advice tomorrow and get back to ya.

Thanks!

Motor running and clutch engaged. Refrigeration turned to high.

While adding refrigerant, the gauge will tell you when it is full.

After you get seals fixed, turn on refrigeration occasionally in winter so the seals don't dry out in the future.

the system called for 134?
per a manual ? or the guy in the shop?

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Originally posted by bendable:
the system called for 134?
per a manual ? or the guy in the shop?

R134A specified in owner's manual.

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Tractor running, AC on but compressor clutch not engaging.

That's your problem and is what you need to troubleshoot. 50 psi is roughly normal (it varies considerably with ambient temperature) for a static charge. It is more than enough to close any low pressure switch, which usually cut off in the neighborhood of 15 psi. Either the clutch isn't getting voltage at all, or it is but the clutch is bad.

You’ve already got a lot of good advice but I want to stress that you should find and fix the leak. If a charge lasts you through the summer, you have a very small leak... maybe your valve stems are leaking.