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Most older systems have seperate low and high presure switches. Most newer systems have pressure senders and a computer makes the same decisions as the switches did in the good old days. These can be tested following the below proceedures but you will need to use extra care as computer cars run the fan at variable speeds. CHRYSLER PRODUCTS DO NOT CYCLE ON THE LOW SWITCH, THEY USE A DIFERENT CONTROL SYSTEM!
Conect your AC guages and check the pressure in the system, and check the switch to see if it is open or closed. I will assume for this example that with the engine off and a 70 F day the pressure will be over 15 psi (Way over) and the switch should be "closed" or on.
Start the vehicle and operate the AC with the inside fan set to low, watch the low pressure guage. The low pressure switch should "Open" or turn off when the pressure drops below the specified level. Most systems off @ about 15 to 17 psi, on about 20 to 25 psi.
The high pressure switch is a little more dificult as there are as many as three of these annoyng things.
1st Fan control low speed or only fan control switch. Run the car, watch your high side guage a single speed fan should start of the higgh pressure switch at the specified pressure 125 PSI to 175 PSi depending on the car. My old Pontiac does not use this switch at all, it just runs the cooling fan when the AC is on.
To test the high and over pressure switches you may have to unplug the cooling fan or use a blanket to cover the radiator. DO NOT OVERHEAT THE ENGINE!
2nd High speed fan same as low speed usualy set between 175 and 225 psi.
3rd Over Pressure switch or emergency switch usually set at 275 to psi.
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Freon leaking through the high pressure switch why?
Switch could be bad or the schraeder valvee the switch screws into could be bad
Oil pressure is reading high on corvette but oil is at correct level. Does this indicate a bad sensor switch?
High oil pressure is good....
Will a bad oil pressure switch cause high oil pressure in a 91 jeep warngler?
It could cause a high reading on the gauge.
How do you check if the low pressure switch on a corvette 1977 is working?
Of which low pressure switch are you speaking? Engine oil pressure switch? If you're checking that, remove the oil pressure sending unit and temporarily put in an oil pressure gauge. If you're checking the AC low pressure switch, pull the switch from the AC low pressure line, Jumper the switch socket and see if the AC compressor comes on. If it does, you either have low refrigerant pressure or a bad switch. If you KNOW the pressure is up and everything else works, you have a bad switch.
Why won't new well pump stop running?
There are several possible reasons. One would be the Pressure Switch being set too high. Another could be a plugged Jet, or Impeller.
Bad oil pressure switch?
Either replace with a known good switch or with a manual oil pressure gauge
What happens when an oil pressure switch goes bad in a 1999 Chevy Tahoe?
Usually you will not get an accurate oil pressure reading either too high or too low. Occasionally they will leak and pump oil through the switch
Air condition clutch won't engage 2000 Chevrolet Silverado?
The most common problem on these trucks will be a bad pressure switch along with a bad pressure switch pigtail.........
Why will your Husky Air Comp not shut off after it is up to pressure?
You have a bad final pressure switch you can buy just the switch at Grainger.
Can a bad engine oil pressure switch make your car run bad?
No, if the oil pressure switch is bad it will just give you a false reading of your oil pressure.
Why is there no power going to the fuel pump in your 94 ford club wagon?
There are a few sensors that will shut off the fuel pump. . Inertia Switch designed to shut down fuel pumps in an accident. aged wiring at switch, overly sensitive switch (age?) etc. . Oil Pressure switch. I believe there is also a low oil pressure switch that will kill the voltage to the pump too if oil pressure is low or if switch or wiring to/from goes bad. orrrrrr... . you got a blown fuse(s) . bad fuel Pumps. There are two (low pressure pump in tank and High pressure elsewhere) or three if you have two fuel tanks. (2 lows in each tank and high elsewhere . dual tank switch issues
How can you tell if the oil pressure sensor is bad or if the oil pump is on a 2002 Dodge Dakota 4.7L?
Remove the oil sending unit and install a mechanical gauge. Start the engine cold and let it warm up to normal operating temperature. It the oil pressure is correct then replace the oil pressure switch.
