SpencerT

Had this question in another thread but I found this video from another user and had to make a thread for it myself.

When I turn my ac on the compressor will turn on and off rapidly 5 or 6 times before coming on completely, causing the rpms to bounce dramatically.


I have the exact same problem.
another user suggested the freon was low and caused the compressor to kick on and off to build pressure?

Any Ideas?

pmesfun

I checked the low side pressure and it was in spec. Then I cleaned the throttle body and removed the neg. cable for a couple minutes. That fixed it, at least for now. Throttle response improved as well.




www.youtube.com/watch?v=M4kiUvf1V2A

SpencerT

yea that was your video I hijacked.

But I doubt you fixed it in that second video. I bet both yours and mine do the exact same thing again tomorrow.

I havent checked any pressures yet but my ac has always been super cold so I really dont suspect a low freon level.

fixmiester

LOL, sorry. You're both in denial. An undercharged system can actually get too cold, and freeze up. You cannot go by outlet temperature; superheat, high-side pressure and Temp difference across the expansion valve/orifice tube are important measurements. Or not, your choice.

pmesfun

A.K.A. take it to a mechanic. I'll do that next weekend.

SpencerT

I ran an AC diagnostic today.
With the car off hold the Auto and Rec. buttons on the ac then start the car and release the buttons.
The only codes I got were 21 and 24. Both of wich I believe are solar sensors so this was no help to me.
May be of use to somebody though.

Anyways I disconnected my battery for a few seconds and that seems to have fixed the problem for now.

pmesfun, if you do take it to a shop, will you let me know the results?

GS4_Fiend

iTrader: (22)

Can you elaborate how does under charge causes what to freeze up and why?

fixmiester

I can't go into a full tutorial here on the thermodynamics of AC systems, Lexus, or otherwise. Suffice it to say that the heat flow dynamics of freon phase state changes are complex, and the systems are specifically engineered for a range of heat transfer capabilities ( i.e. BTU/hr). The ambient and cabin temps, the delivery rate of condensed (hi pressure) freon, the flash pool size and air flow across the evap are all variables that the system has to deal with, so it will not perform well outside the design tolerances. The amount of freon in the system has a design tolerance; too little will not generate a flash pool in the right area of the evaporator, and could develop frost on the coils that could block air flow. Too much freon can develop extremely high pressures, and temperatures, that would damage the system. There are simple DIY kits out there that, while not professional, do allow the average guy to at least determine if the system is low on charge, and remedy it. Beyond that, take it to a shop.

Steve