FJ60 A/C problems need advice!!

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

J

jpeterson

10 Year
Joined
Mar 15, 2012
Threads
8
Messages
33
Location
San Jose, CA
82 fj60. Has r135a retrofit, done by previous owner.


Fully charged system. a/c will run for about 45 seconds to a minute then trip the breaker. After doing some digging around I figured the clutch was dragging, thus tripping the breaker. Replaced with new clutch. Still same problem. After about a minute, ac breaker trips. During that first minute the ac blows very cold, both high and low side pressures look good on gauges, and its as if its ready to cycle off when the breaker trips. Idle up works. I know It couldn't be a short in the signal wire from the ac amplifier, or it would trip the breaker instantly when ac is turned on.

My thoughts:
Bad ac amplifier? I took it apart, looked for bad solder joints, burnt spots. None that I could see.
Is there a low pressure switch? I couldn't find it visually. Where would it be located if my rig had one (82) and could it cause the breaker to trip?
Evap thermistor?

Any ideas input experience would be greatly appreciated. Thanks in advance!!!

Josh
 
I was told by Cruiser shop that my 87 60 has a low pressure switch. The 36262E FSM (I think it was printed in 86?) shows a pressure switch between the fan and the evaporator box, says to remove the glovebox to access it.

Not sure why it would trip the breaker though? But I don't know how to work on AC.
 
The low pressure switch for the fj60 is in the low pressure side of the a/c system. The purpose of the switch is to disable the a/c system when there is not enough refrigerant in the system, which would damage the compressor.

It sounds like you have just enough pressure to satisfy the low pressure switch when the system is static, but not enough once the compressor gets spinning. Once the compressor gets up to speed, the pressure on the low pressure side will drop, causing the low pressure switch to activate if there is not enough refrigerant in the system.
 
The pressure switch is inside the evaporator box. You could probably test it by probing the AC amplifier but I'm not sure exactly which wire to check since I don't have the FSM here with me.

iETibOH.jpg
 
Thanks all for the help! If I jump the yellow/green wire (which comes form the pressure switch to the amplifier) to ground, would that cut out the pressure switch completely? Just to determine if that is what's tripping my breaker. I can just cut the wire before the amplifier connector. Hope that's making sense.

Could a short in the pressure switch itself be enough to trip the breaker? That's my only question. My understanding is that if the the low pressure switch is functional, and it sees low pressure on the low side, it will just cut power to the clutch, not through the breaker...
 
Judging by the pressures on the a/c machine gauge, i believe the compressor is working correctly, that's why I think it's an electrical fault if some kind.
 
So you have put a set of gauges on it? what exactly are your numbers?
 
Have you tried replacing the breaker? It might have gone bad
 
I have replaced the breaker. I thought it might be weak from the get go. No luck. I do have a set of gauges hooked up to it. I work in a shop where we have the whole evacuate/recharger machine. Low side is around 45, high side is around 150.
 
Have you checked the thermistor to make sure it's reading properly? Seems like it could go bad and shut off the compressor at a higher temperature than it's supposed to.

Also, some AC amps have a temperature control knob, if that's set too high it might cycle the compressor too soon.

Edit: Ah, sorry, just realized the basic AC amp troubleshooting is probably not what you're after since the breaker keeps tripping. Have you checked for a short in the wire that powers the compressor? You might need to check out the schematic for the AC system in the FSM on page AC-9 and test everything in the circuit after the breaker.
 
Last edited:
New development. After testing each circuit to the ac amplifier connector, i was testing it with the fan speed on low. To my surprise it never blew the circuit. So, i tried every speed, and it only blows the circuit on hight speed. So naturally I though blower motor or resistor. Replaced with parts from another 60 at the shop just to see if it either would fix it. No luck, still blows the circuit on high fan speed, only when ac is running. So now I am starting to think either

Ac switch
Blower motor switch

Or

Ac amplifier. I ordered one from sor, coming Monday. Any other thoughts??

Thanks for all your help so far.
 
If you have access to a different blower motor you may want to swap them. It sounds like a high current draw and the motor could be the culprit.
 
I think you're onto it, sounds like either the blower switch or the fan. A bit of contact cleaner on the blower switch to try to clean it up and lower the resistance probably wouldn't hurt, not sure it would make any difference but if you're running out of things to try... contact cleaner on everything.
 
is the rear heater on when it pops. the amp seems to be in the circuit after the 10a fuse so I don't know how it can pop the 30a breaker and not the fuse.

WP_000723.webp
 
Yesterday I thought the fan for sure to as it too. We had a 62 in the shop yesterday, so I swapped the fan motor and the resistor quickly to see if either of them would fix it, neither did.

I have not had the rear heater on when I have been testing, so I don't think that could be it.

Going to take apart the blower switch and ac swith today and inspect and clean. See If I can get lucky.
 
The only reason I suspect the amp is a possibility is that it only happens on high fan speed with the ac on. Ac off, never blows the breaker. I look at the diagram again.
 
In the wiring diagram it looks like power to the blower motor goes through the heater relay. Could be that the relay contacts are worn out and have enough resistance to blow the breaker. If you don't have a spare heater relay, you could probably jumper the wires just to test whether the breaker blows.
 
Hey all. Decided to start again and do some investigating. Just took apart the blower motor, cleaned and installed new brushes. Cleaned heater relay contacts. Cleaned blower motor switch, and ac switch. Still blowing the breaker on high fan speed. A couple weeks ago it started to blow the breaker with the ac not on/high fan speed. So I am begining to think it has nothing to do with the ac. I noticed that the wires at the breaker get very hot then the breaker trips. The wires at the breaker are getting very brittle. Maybe the combination of years of high resistance in that circuit, and a weak breaker now be the cause?
 
Last edited:
You must log in or register to reply here.

Share this page

Back
Top Bottom