AC Troubles

It finally has started to warm up outside so I decided to go ahead and test my AC system to see if it needs a refrigerant recharge. I tried to follow the procedure in my Haynes manual to do this. The only trouble is that procedure requires the compressor to engage while the AC is turned on maximum. My compressor doesn't engage at all. My question is whether I should continue with my plans to recharge the refrigerant. I don't want to do any damage or waste money on the recharge if it won't have any effect. Any advice is greatly appreciated.

If the low side pressure, (at the accumulator) is less than approximately 40psi, the clutch cycling switch will not allow the compressor clutch to engage. If the system is low on refrigerant, there is a leak somewhere; Adding refrigerant might allow the compressor clutch to engage, until it leaks out again.

It finally has started to warm up outside so I decided to go ahead and test my AC system to see if it needs a refrigerant recharge. I tried to follow the procedure in my Haynes manual to do this. The only trouble is that procedure requires the compressor to engage while the AC is turned on maximum. My compressor doesn't engage at all. My question is whether I should continue with my plans to recharge the refrigerant. I don't want to do any damage or waste money on the recharge if it won't have any effect. Any advice is greatly appreciated.

What year?
R-134 a or r-12 system.

As old mater said you have to have pressure in system for compresser to turn on.

To do a proper recharge or test system you will need a low and high side AC gauge set up.

Like one of these gauge sets.

http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

The one hose one gauge walmart recharge kit is a no no.

Does you system have any pressure?
If so.
Post back pressure reading.

My 1997 Jimmy has an R-134a AC set-up. I was able to take a few pressure readings this afternoon after attempting to add refrigerant. I jumped the accumulator pressure switch and the compressor was able to engage. I then tried to add a bit of refrigerant but none ever seemed to enter the system. After I attempted to add the refrigerant I removed the jump wire and reinstalled the switch wire. At this point I started the engine with the AC on max and the compressor was engaging on its own with readings from the low side pressure switch. It is about 75 degrees outside right now and I am getting a range of low side pressure readings from 15 psi to 55 psi. The compressor engages at 55 psi then the low side pressure drops to 15 psi at which point the compressor disengages. This seems backward to me but I have little experience with AC systems.

Thanks for the gauge suggestion MT but I need to avoid spending quite that much at the moment if possible. Do the pressure readings I provided help at all?

The clutch cycling switch turns on the compressor at approx 42psi and shuts it off at approx 22psi. The average should be 32psi. If the average is below 32, the evaporator will ice up and there will be no air flow through it. If the average is above 32psi, the air flow will be too warm, (insufficient cooling). On systems with clutch cycling switches, the ONLY way to know how much refrigerant is in the system is to drain, evacuate and recharge it. If the system is not charged with the correct amount of refrigerant, the pressure readings are meaningless.

My 1997 Jimmy has an R-134a AC set-up. I was able to take a few pressure readings this afternoon after attempting to add refrigerant. I jumped the accumulator pressure switch and the compressor was able to engage. I then tried to add a bit of refrigerant but none ever seemed to enter the system. After I attempted to add the refrigerant I removed the jump wire and reinstalled the switch wire. At this point I started the engine with the AC on max and the compressor was engaging on its own with readings from the low side pressure switch. It is about 75 degrees outside right now and I am getting a range of low side pressure readings from 15 psi to 55 psi. The compressor engages at 55 psi then the low side pressure drops to 15 psi at which point the compressor disengages. This seems backward to me but I have little experience with AC systems.

Thanks for the gauge suggestion MT but I need to avoid spending quite that much at the moment if possible. Do the pressure readings I provided help at all?

They only suggest a low charge.
Better to rent or borrow or buy the proper gauges than to mess up your hole AC system .

Check your local parts places for rental or loaner gauges.
And as said them walmart one hose one gauge death kits are a no no.

With compressor running it should suck in R-134a on low side fitting.
If not your low side hose fitting is not opening schrader valve.

But to do a proper and safe charge and to know if proper charge and system is working right you need both low side and high side gauges.

And as old master said it is best to evacuate/pump out and do a set charge.
The S-15 jimmy takes 2 lbs /32 oz of R-134a.
The days of add a can are long gone.
Newer systems 2 -3 oz over or under charge is not good.

Thanks for the advice guys. I'll set up a refrigerant drain at an AC place, find a high side/low side pressure gauge to borrow and check back in.

Thanks for the advice guys. I'll set up a refrigerant drain at an AC place, find a high side/low side pressure gauge to borrow and check back in.

Sounds like a winner.
Good Luck and let us know how it goes.