hi everyone. just joined yotatech. i have a 98 4runner 3.4 (just bought in november) and am having a a/c problem. tried searching everything and still cant get a good answer. my a/c is not working, green light on button comes on, but the clutch does not engage. able to spin clutch by hand (engine off of course) so the compressor is not seized. there is some pressure in the low pressure line, but i don't think you can get an accurate reading until the compressor is running, correct? so i think its either the relay or low pressure switch. i believe the heater relay controls the a/c as well, correct? what are some ways to test? run a jumper straight to the compressor? how is that done? (dont want to break something, myself included) i consider myself a pretty good mechanic but i have never been very good with troubleshooting electrical problems and am not very good with a/c. thanks for any help.

 

i just fixed mine, it didnt work even after lots of friends and trusted toyota mech's looked at it, i took it to a local and found out the cooling fan was not receiving a negative charge from the battery through the normal relay in the fuse box, so we hooked up another relay and fixed it.

now i dont know if the 3rd gen A/C is the same in any way to the 2nd gen A/C but that is what my problem was. and it all sounds the same...hope it helps

 

dont know about your issue but mine was blowing hot and 1034$ later.... ICE cold

 

York conversion. For a trail rig onboard air outweighs the need for A/C.

 

Welcome to Yotatech. I lived in Spokane before I moved to Norcal a few years ago. I miss the area up there!

 

Spinning the clutch by hand just spins the clutch, you can't tell if the compressor is seized. Try jumping a wire from the +ve battery terminal to the compressor clutch wire. With the engine off you should hear the clutch engaging. If it does do the same with the engine running, if the compressor is seized the belt will start smoking. If the compressor runs than the refrigerant could just be low. Don't run the compressor very long like this, if the refrigerant level is low you can damage it.

 

update. so i jumped the compressor and it worked so that allowed me to start filling with r134. it was lower then i thought it was. while filling it started to blow nice and cool. so i hooked the compressor back the way it was supposed to and when i turned on the a/c button the compressor kicked on like it should but after running for 15 or twenty seconds it kicked back off and continued to cycle itself off and on. i tried to idle up the engine but that didn't make any difference. so is this the low pressure sensor saying their still isn't quite enough coolant? at least i know that most everything works almost perfect. thanks for any help.

 

Couple things.
1. Massive leak somewhere. An above post commented about needing a certian psi for it to run.. so when you get below it; its turning itself off. If your filling it up, its work for a bit and then not.. you have a blow seal or leak somewhere.

2. Less possible, I have a 2nd gen and had this issue where when the A/C was on, it ran like a dream. Nice old school r-12a, cold. But getting it to actually turn on was kinda off and on. Figured out the rpm shutoff was messed up. I have no idea how it is on the 3rds, but on the 2nd theres a specific rpm limit to it. Below that and the pressure of the engine running the a/c would bog it down so it cuts the compressor off. I switched out the circuit and now it works great.



My first bet though, LEAK. Take it to a prof. and have them look for leaks. They will do a nifty vacumn test to let you know.

 

A few of you need to study up on your AC systems....

Yes, you have a leak somewhere. That is why you had low refridgerant.

However, the system is designed to kick on and off. It should never stay engaged the entire time. Its perfectly normal (unles the button is turning on and off, thats not right. But if just the clutch is engaging and disengaging, that IS right)

Take it to a shop and have a leak test performed, and they will be able to tell you where the leak(s) are.

 

Mine has a leak. I don't know why but I never fixed it. It has been broken over a year now and I am finally getting the right hose to fix it... Needless to say, I will be very thankful when I do.

My seat probably has so much sweat in it. I live in the desert and last summer it was 113 Degrees for like a week! I almost passed out one day from heat exhaustion while driving. My senses started slowing down and it was really freaky...

 

Thats gross, and I know from experience. My first car was an 89' subaru station wagon without A/C. I lived down in the south with normal 98-110 summer days plus humidity. Rough! ROUGH!

 

Fast cycling is an indication of an overcharge. If the low side pressure exceeds ~50psi it will open the pressure switch and cause your symptoms. Low side pressure should be between ~40 - 50 depending on ambient temp.

If the low side pressure jumps to a vacuum that is an indication of icing caused by moisture but I'd bet on overcharge.

 

I don't think it is overcharged cause my hand held guage says that it was fine and if anything could have still used some more. i never got a reading on the pressure gauge that indicated it was overcharged. the highest i got the pressure (according to the gauge on the fill hose and my hand held gauge) was around 26psi which is still a little low. i will double check again though just to make sure. the pressure must have been really low right from the start so i might take it to a shop and have it vacuum tested for any leaks.

 

When I topped mine up with one of those cans of R124a I went until the guage was at the top of the green section, almost into the red. It's worked fine for almost 2 years since then.
Like DeathCougar said all A/C systems cycle on and off, though mine doesn't do it as oftern as 15-20 seconds.

 

new problem! the a/c is now working except for the fact it seems to be cycling on and off faster then it should. but now the a/c will run even when the a/c switch is not on. the fan has to be on but not the a/c dash switch. what the hell! does that sound like a dash switch problem or a relay problem. is the a/c relay the one that is labeled as heater? cause i don't see an a/c specific one. i am going to have it all leak tested at a shop but i want to know everything else works the way it should first so i don't get screwed somehow. thanks for any help.

 

There you go... Low pressure cutoff is 28psi.

 

its supposed to operate even without the switch pushed. It keeps the air in the vehicle dry, thus eliminating the fog problem.

Your truck is NORMAL.

Get the leak fixed, and you will be golden.

 

the a/c cycling off and on (quite a bit) is normal? i have never heard of that. it does make some sense though but it seems like it would hurt the EPA fuel mileage rating. it still seems to me like the whole thing has a mind of its own. i could tell the a/c was running (through the cold air) all the way home from work yesterday and the switch wasn't turned on once. also when i actually turn on the a/c it doesn't act any differently then when i don't have it on, as long as the fan is on the a/c is running intermittently as it wishes. even with the a/c switch taken out of the dash (to insure the switch isn't the problem) it still acts the same. ????? thanks for any help.

 

If you are using your defroster, this will happen. The defroster uses the AC to take the moisture out of the air. If not, then it sounds like yo might have a frozen contact in the system somewhere. As for the cycling, that is normal. Once the refrigerant is cool enough, it will cycle on and off to keep it at pressure and temp. This allows the system to be "on" but not putting the drag on the engine and KILLING your MPG. If anything, sounds like you have a leak. But thats a best guess from far away.

 

dude just take it to a shop! you are trying to fix it without the proper tools and by asking people that have not seen your truck. You have a leak, freon does not disapear or disolve or wear out. Your system needs to be checked for leaks, have gauges on both and high side. Not to mention vacummed for moisture.