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Low pressure high, high pressure low, short cycle

Rover Dog on Mon September 10, 2007 4:17 PM User is offline

Year: 1993
Make: Land Rover
Model: Range Rover
Engine Size: 4.2 L
Refrigerant Type: R-12
Ambient Temp: 89
Pressure Low: 60
Pressure High: 110
Country of Origin: United Kingdom

During the last heat wave on the west coast, I recharged the system until the bubbles in the sight glass disappeared. Now the compressor cycles on and off frequently and naturally there is no cooling since the compressor doesn't run long enough. Does this sound like a thermostat issue more than a compressor issue? I picked up the truck in January, so I didn't have a need to run any A/C back then.

What other issues am I facing at this point? I have yet to bring it in the shop, but wanted to see if I had made any fatal mistakes.

Chick on Mon September 10, 2007 4:33 PM User is offlineView users profile

You have to find and fix the leak..Dids you use "real" R12 to charge the system until the bubbles disappeared?? or an R12 substitute?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Rover Dog on Mon September 10, 2007 6:34 PM User is offline

Prior to me picking up the truck, it must have sat for many months. I just assumed the freon was "lost" over several years. I used real R-12 for recharging the system, but I can't vouch for what was left in the original system, but it wasn't very much.

The clutch comes on and runs the compressor for about 3 seconds and then switches off for about 30 seconds and then it repeats itself. When the truck is moving the front seats get some "cool" air, but there isn't enough to reach the rear seats. The truck is a long wheel base model so the rear passengers are much further away.

Chick on Mon September 10, 2007 6:43 PM User is offlineView users profile

Until you fix the leak, try not to use the AC sysytem. The constant cycling is not good for the compressor, and little oil movement will cause it to destruct... If need be add some UV dye to the system, charge it back up and run it til the dye comes out. Use a UV light and it should be fairly easy to spot..If not, a sniffer will find it..Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Rover Dog on Sun November 18, 2007 2:39 PM User is offline

The update is that the compressor has been replaced with a brand new SD-709 along with a new receiver drier. The shop charged it fully with new R-12. However, the compressor doesn't stay on for more than a few revolutions and shuts off for a minute or so and repeats this cycle. The mechanic suspects it's just an electrical issue, so I'm suspecting it's the thermostatic switch.

If I'm starting with a new compressor, drier and a full system, then where would my issues be?

Thanks in advance for your comments or suggestions.

NickD on Sun November 18, 2007 6:33 PM User is offline

What happens to the pressures if you were to hot wire the compressor clutch, directly to the battery, I like using a remote starter switch for this so I can quickly turn it off if the pressures go out of bounds. If pressures look great and you get fantastic cooling, then you know for sure you have an electrical problem. But if that low side drops down to the floor, switch it off and follow Chick's advice. This will take all but a couple of minutes.

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