Climate Control

Compressor Functions Intermittently

Compressor Functions Intermittently

Rex McIntosh wrote:
> Can someone tell me where the temp switch is that cuases the compressor to cycle
> on and off?
> Every thing else in the chain seems to be fine, but some times the airson
> compressor just will not go!

After having my TB tensioned by the dealer last Spring, my A/C compressor would not engage. The same week I attended a Tech session sponsored by Potomac PCA, and the master mechanic for the sponsoring dealership identified the culprit; a bad connection at the male(red wire)/female(black wire) plugs for the compressor circuit found in front of engine on passenger side (in front of cover for TB). The mechnaic explained that this is fairly common after a TB tension/replacement. If you've had a recent tensioning, I'd give this connection a look. You might want to check it anyway for corrosion.

Joe Rausa '89S4

The diagnostic for this runs from testing at the connector to the clutch itself, through the connector at the side/top of the radiator sheet, then at the pressure switch on the dryer.

The temp switch is located at the top of engine compartment, under the plastic "rain shield" at the base of the windscreen. On my '89, the switch is retained by an aluminum angle bracket right about the center of the car, has two spade connectors, and has the probe capillary tube running to the left (american driver's side) a few inches before it drops into the evaporator housing.

FWIW, I went through a similar diagnosis on mine early last summer. Low freon gas level will sometimes cause erratic operation of the compressor, and is related to ambient air temp as much as anything if the level is just right.

My gas level was OK, and the problem ended up being a defective relay on the climate control module in the center console. The relay on the controller from the factory is underspec'd for the clutch coil's load. I did a little 'field engineering change' that adds an external relay. If you find that the coil voltage is OK when the coil is not attached, yet drops when the coil is plugged in, check for that same symptom when measuing at the terminals on the thermal freeze switch. If you have low voltage under load at that switch, you are a candidate for a new console controller or the dr's external relay fix.

Here is a downloadable diagram of the modification, with instructions. You can view it and print it out using Adobe's Acrobat Reader. If you do not have this common program installed on your computer you can get a free copy directly from Adobe

dr bob

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