Tip & How-To about Chevrolet 1500

Better fuel mileage in the winter months

To get better gas mileage in the winter,Pop the ole hood,and unplug the ac compressor,or the low side pressure switch so the ac compressor can not come on.Lot of people do not know that when you use your defrost,the ac compressor come s on,and it will cycle on,and off,causing the engine to rev up,and down.Now you most of the time will not notice the reving up ,and down,because of the load of the compressor.The compressor puts a load on the engine there fore using more fuel.Who needs ac in the winter?

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1992 Mercury sable,loud pop then looks like steam coming up out of right side of hood AC stopped cooling blower still works

Sounds like AC line burst or compressor safety release drained system (less likely). Sometimes a AC system is overcharged. There are 2 safety relays to protect the system and one is for low pressure and the other is for high pressure. These prevent the compressor from getting power to the compressor clutch.

The freon gas reacts to outside air temperature. Pressure is relative to temperature. Making up numbers for example a 50 degree temp may have 30psi but a 100 degree temp may climb to 100psi and cause relays to pop.

You need to have the system pressure checked. There are devices called sniffers for leak detection. See a Pro If someone fooled with this AC it may have blown a seal or line.

Jul 11, 2017 | Mercury Sable Cars & Trucks

1 Answer

Location of the Ac low pressure switch 2007 Mkz

The low pressure switch (also known as the AC compressor switch) will be under the hood, it will be located in the low side AC line from the AC compressor, this is the larger of the two lines from the AC compressor. See picture below, looks like it has a three wire connector. Also what is the AC doing that makes you think this switch is defective? Cycling on and off constantly?


Jun 26, 2016 | 2007 Lincoln MKZ

1 Answer

My AC on my 1996 grand Marquis's will not turn on at all

Unfortunately all the reasons for this problem require an AC person.Low gas in the system will cause the low side pressure switch to pop out. No gas in the system will cause the same thing.To much gas will cause the high side pressure switch to cut out.The clutch on your AC compressor may not be engaging.Your compressor itself might be toast.So there is no simple answer to your question and this is not something that your average Joe can fix.You need to have the system checked to see if it has a leak somewhere and then attended to.sorry but I have no easy quick solution for you.You have to take it in somewhere. good luck

Apr 28, 2014 | Cars & Trucks

3 Answers

A/C Compressor not kicking on

The power to run the compressor clutch coil goes from the battery, to the AC Clutch Relay, somewere in the engine compartment fuse box, then it goes to the positive side of the AC compressor clutch coil; goes thru the coil, activating the compressor, and then goes to complete the circuit through another switch (high pressure protection switch) in the back of the AC compressor and finally reaching negative or Ground.

Disconnect the AC compressor clutch connector and using a 12 V bulb with 2 wires (test lamp) check the following:

1.- connect 1 lamp wire to battery neg; with the other check both pins at connector with the AC in the RUN (AC and ignition switch on ) you should have power in one side.

2.- connect 1 lamp wire to battery positive and with the other check both pins at connector, lamp should light getting the ground from the clutch connector thru the high pressure compressor switch to ground.

On the other side what makes the relay close and let the power flow to the clutch works with the low pressure switch, (if the freon pressure is too low it opens and kills the ground to the relay coil and that kills the compressor), that low pressure switch is in the low pressure side of the freon tubing, the fat pipe that comes from inside the firewall into the accumulator/dryer, a big aluminum cylinder sitting on the right side of the engine compartment in GM cars.

To know if the low press switch is the cause you can unplug it and connect both legs with a paper clip for a minute or two, no more, you don't want to damage the compressor. anyway if jumping the switch makes the compressor come alive and kick in, you either have low freon pressure or a bad switch; it's time for the pressure gauges and check how the compressor is pumping and that is better left to a pro.

By the way you said that your system is a R-12 system, have you considered switching to R-134a the new "ozone friendly" freon? to do that you need to evacuate the system with a recycling machine and pull vacuum in your AC, if it holds the vacuum for a while, then you can be sure that there are not leaks and then dump 1.5 or 2 pound (check the labels in the engine compartment) of R-134a into your system. it will be a good idea to put some fluorescent leak detecting dye in the system to check for leaks, just in case..

Jun 13, 2009 | 1992 Oldsmobile 88

1 Answer

AC Problems

If there is no gas in the system it as you pointed out the low pressure switch will shut the power to the clutch in the compressor off. your pressureswitch should be located near the dryer at the front of your Benz. You could try and bridge it to see if the compressor engages, how ever DO NOT try and keep it engaged without gas in the system or you may find yourself having to change the compressor again.

Jul 25, 2008 | 1988 Mercedes-Benz 190

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