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Discussion Starter #1
So my Ac was working excellent and last month i ihad replaced the hi speed blower relay so all my speeds were working. well last nite i went out and the hi speed is not working and the ac clutch is not engaging. Any thing i should check?
 

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The high speed blower relay is fed from fusable link A.
As for the clutch, the pressure switch controls it. You may have lost the charge. Throw a voltmeter on the clutch. Check for 12v with a/c on.
 

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Bird, Good morning, is it possible the AC relay coudlve gone?
It's possible. My schematic does not show pin #s. I can tell you the black and orange is the coil. Check for continuity across there with the harness disconnected. The dark blu to purple should show continuity. When 12 volts is applied, red to purple should show continuity. Hope this helps.

The high speed relay and the clutch circuit only commonality is the fuse. 25A.

If the blower runs at all, they are un-related.
 

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Once you get the blower running on all the speeds, you can also check for low charge in the system- there's a 2 wire connector on the dryer, check for power there, and then you can jump the 2 terminals and see if the clutch comes on. Don't run it for very long. Just a quick jump and see if it does start. If it does, either the system is low or the pressure switch died. Use a meter and check the switch, it should have continuity if it's OK and the system is charged. If there's no circuit thru the switch, it can be changed without dischatging the system. There's a schrader valve under it. Unscrew the old one and install a new one..
 

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AS I RECALL, up to M/Year 78 anyway....the HS relay is fed by a heavy orange wire coming off a white fuse clip near the horn relay on the driver's fender liner.....about 3" long....it's a very famous failure item on all GM cars of the era...so much so I replace it and it's 30 amp fuse with a small spade fuse connector, and kiss the problem good bye......new white fuse connectors that look stock are no damn good....
 

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Discussion Starter #9
seems like it was the low pressure switch because i jumped it and surely enough the clutch engaged.. Thanks alot guys.. DC is truly freakin amazing .. cheers:cheers:
 

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Discussion Starter #10
i was checking the gas pressure and it is low.. Now my question is i was charging it and while the clutch is engaged it seems the gas level is low now when it disengages, the pressure goes up to a little above filled... this is after i recharged it..... so do i check the pressure with the clutch engaged or disengaged?
 

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The clutch HAS to be engaged to check pressure, but with the system full the pressure will be up and down, cycling with the clutch. Usually, the lo side will be between 26 and 35 psig, and the hi side will be 2-1/2 times the outside air temp. That's with R-12, but I suspect R-134 will be somewhere in the 'hood.

:cheers:
 

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To simulate road conditions:

Run ac with hood open
Controls set to max ac with windows open (simulates road conditions with heat load and prevents under hood air from entering evaporator)
Run for 5 minutes and get hi and low pressures, ambient temp and center vent temp.
Your compressor should not cycle much unless you are properly full of refrigerant.

Post what you got and what refrigerant you're using.
 

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Discussion Starter #13
i have R-143 and when it engages, psi goes to 5 and then when it disengages it shoots higher like if it was over filled a bit.. Im goin to take it in because i found a leak
 

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That was my next step.:laughing:

Get yourself some 134, not 143:D ,with some dye in it and put it in until the low side is above 30psi. It's pretty cheap. Depending on the age of the components, you may well have more than 1leak and since you have the gauges, you may consider repairing it yourself.
So you press switch was good after all.

Where is the leak you found?
 

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Discussion Starter #15
yea switch was okay. its leaky on the low side fittin which enters the compressor and the high side has another leak
 

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Get a pack of replacement orings and go for it.

At most a shop will just have to suck it down and charge it for you if you don't have a vacuum pump.
 
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