where are my AC guys at? Compressor cycling

99 Tacoma, AC compressor comes on for 5-7 seconds, then is off for around 1 minute. Then comes back on for 5-7 seconds, and is off for about a minute. This cycle repeats until I move the knob off Defrost, or turn the AC switch off..


I have tried jumping the AC pressure switch, this leads to the same results.

I know, its winter, but I was trying to track down a squeak from one of the accessory pulleys, and figured if the AC compressor clutch was locked (AC on) the AC Idler pulley bearing would not turn, thus eliminating the noise if it was at fault.

 

Check your refridgerant. Might be low.

 

jumping the pressure switch would have told the AC amp the refrigerant was full.......

 

I'm not saying its super low, its just not filled to proper standards. Thats why the compressor would kick on and off so quickly.

 

Depending on IAT the AC compressor will just engage briefly or engage for an extended period of time

 

and I am saying that I by passed the pressure switch completely. The pressure switch is a switch. It is either On or OFF. Jumping the two electrical pins together would be like the switch being CLOSE aka ON. With the Jumper in, the AC AMP "thinks" there is plenty of pressure/ Freon....

 

What is the reason for bypassing the switch and jumping the plug? If you're trying to trick the compressor on then you accomplished that.

Can we move pass that and to the 'why' you're jumping it?

 

IAT, Intake Air Temp? Im reading 40*~ . Ive never ever had my compressor cycle like this. I am aware of a thermistor that is mounted to the evaporator core. I have not been able to track down diagnostic info yet though.....

 

Correct, I don’t remember the exact spec but it does play a big factor in the engagement. It may be driven of a secondary thermoresistor than IAT...I’ve seen them both ways

 

See attached.

 

the only reason the pressure switch is present in the system is to insure there is refrigerant in the system above a certain pressure... IF there is a leak or the pressure drops below a certain point, the pressure switch opens, and the AC amp will turn off the compressor... by jumping the pressure switch, you are telling the AC amp that there is enough pressure in the lines to run the compressor. jumping the switch is the poor mans way of testing the rest of the AC system. If you jump the switch and the AC compressor runs, but wont run with the switch jumped, then there is not enough freon in the system.. For me, jumping the pressure switch did not change the AC compressor cycling. thus, I must have enough pressure. Also, checking Ohms on the switch, I get .1, meaning, switch closed.....

 

2 more.

 

I think this should all you need.

 

I know what that switch is for, but I want to know why you need to jump it? If the compressor isn't kicking on like it should when you turn on the a/c then you need to get gauges on there to for refridgerant and pressure readings.

 

Not too sure how the taco system operates, but most the vehicles I work on also have a high side switch that will kick off the compressor if you get too high of pressure on the high side. Maybe you're orifice/txv is plugged/restricted and you're getting too high of pressure on the high side.

 

I jumped the pressure switch to see if it changed the cycling. I low freon was the problem, the switch might be opening and closing. by jumping the switch I am simulating a closed pressure switch... I really dont know how else to explain myself..



thank you for the documents though. I will use them.

 

Yeah don't do that, at least you know the compressor is working fine. If you're low might want to inject some dye to locate the leak. Sometimes it could also be the evap being clogged with debri. Check that too.

 

I understand that jumping the switch is not the best for it, but for a few seconds, I dont see what it could hurt. Regardless, jumping the switch DID NOT change the cycling. So, I am ASSUMING I have proper pressure... I left the switch bypassed for about 2 minutes, and the compressor still cycled on for 5 seconds, and off for a minute, and repeat.

when you say clogged, do you mean leafs or something inside the evap.

 

No, there's a couple things that can fail inside where the Freon goes. 1, your compressor, 2. There's a desiccant bag in your accumulator/drier. If the compressor comes apart or that desiccant bag ruptures, it can clog up the funnel point for your system (the orifice tube or txv) this would cause high pressure on the high side

 

Is it possible that the subfreezing temps (10-20*F) are causing the AC system to cycle and my system is actually working fine and I am just crazy?