jbcampbell21

I have an '88 4runner SR5. My A/C has quit working. When i push the A/C button the light doesn't come on anymore and the air is hot. I checked the fuse behind the glovebox and it was blown. I replaced it and it didn't last 5 minutes. I'm not sure if it is related but the first two fan levels have quit working in the last year leaving me with only the highest two fan levels to circulate air. I am not sure where to start.
Also, I have been having problems with starting my truck with the A/C on. I have to turn it off in order for it to crank bt I have had no problems since the fuse has blown. This doesn't seem like a coincidence but maybe I am wrong

myyota

The resistor for the blower is bad, that`s why you only have the high settings, you need to replace the blower resistor and you will get the lower speeds back.

For the a/c, its possible that the compressor clutch is bad or locked up causing the starting problems and the a/c not to work.

Hadmatt54

The blower motor is connected to a resistor bank that drops the voltage in the circuit and allows you to have several fan speeds. On low speed the total resistance of the bank is in the circuit. on the 2nd. speed only 2/3 of the resistance is in the circuit, the 3rd. speed only 1/3 of the resistance is in the circuit and on high none of the resistance is in the circuit and the blower is operating on a full 12 volts.
Resistors can fail two ways, they can burn open or they can short.
You lost the lower two fan speeds because the blower resistor that is in the circuit opened between the 2nd. and 3rd. terminals of the resistor.
I am assuming that the fuse you replaced was the 20a. heater fuse and not the 10a, A/C fuse, if so then I suspect the resistor has failed completely now and shorted to ground.
Once you lost your blower circuit your A/C will not work as the 10a. A/C fuse, switch and amplifier are powered up with the closing of the heater relay.
Other than a short dropping the system voltage not allowing a start I don't know why your starting problem would be related to the A/C system.
I've been looking at the wiring diagrams & if it is the heater fuse that you are blowing, and the resistor is shorted then any of the first three speeds will blow the fuse if you attempt to turn on the blower. Also if the problem was in the A/C then you would blow the 10a. A/C fuse, so try this: Turn you blower control to high replace the 20a. Heater fuse and turn the key to the on (run) position. If the problem is the resistor, the blower motor should be working on high. If it doesn't then the problem is in the relay or the wiring from the relay to the blower switch or blower motor circuit. If the blower works, try starting the vehicle with the blower still on high, if the vehicle starts, push the A/C button, your A/C should work. If this works then your resistor is the culprit and you only need to replace that.

808nickh

im not sure how old this forum is or if anyone uses it at all but i just recently had a a/c problem my a/c was working perfect and then today it just blew hot air im not sure what the problem is but the compressor is not turning on, but my a/c light still lights up green i have no idea were to start looking i have never had an a/c problem before

Hadmatt54

808nickh:
You don't say what year your truck is and sometimes A/C systems may change components between years. I could give you the whole write-up of how the A/C system works, but without knowing what truck you have what I give you might not apply and without a wiring diagram to follow what I'm saying, I'd lose you at terminal 6 of the A/C amplifier.
What I do know from what you said is that the A/C fuse, the switch and light are working the way they are supposed to. Assuming that none of the big components are toast (the A/C signal section of the ECU, A/C amplifier, magnetic clutch on the compressor) there are two smaller components that will prevent your A/C from working.(A/C low pressure switch and the A/C thermistor). If the refrigerant pressure is low in your system or if your pressure switch is faulty your A/C will not come on. If your thermistor picks up that the evaporator temperature is low (37 degrees or less) or if it is faulty the system will not come on and the amplifier receives a signal from your ignition coil and ignitor, if engine speed is low (600rpm. or less) your system will not come on. That would most likely be a wiring issue as your truck would not start if your coil and ignitor were faulty. I'm no expert in A/C systems, but it seems to me that loss of refrigerant is the main cause of problems so that would be the first place that I would look. Go to an A/C shop and verify that the pressure in your system is ok (30 psi. or greater), if it is then you will have to start looking at the sensors.

808nickh

sorry its an 85 toyota 4runner sr5 22re thanks for the advice i havent double cheaked my a/c fuse but as far as i know if the fuse was blown my a/c light on my dash wouldnt come on, also my truck idles at about 750 and when i turn my a/c on the idle goes up to compinsate for the extra pull on the motor well that is not happening eather but ill cheak into the pressure in my system that sounds like a good idea

BMcEL

I know this is an old thread but I'm having similar issues...figured I'd post here since there is some good info above. I checked the low side pressure, topped the system off, and it worked fine for about 10 minutes before the AC light turned off and the compressor clutch released. My AC fuse popped so I put a 30a in because it was all I had left, and it fried a circuit in the amplifier (couldn't withstand 30 amps I guess). I soldered the circuit in the amplifier back together so now I'm back to where I started. System is charged, the thermistor, heater relay, AC cutoff relay, and pressure switches are good. Now, I know that the first blower switch position (lowest setting) is dead, so my question is could the blower switch cause the AC fuse to blow? I'm still in the process of troubleshooting and haven't tried to repair the blower switch or checked the circuit between the amplifier and compressor yet, but any input would be greatly appreciated.

*Edit* Just checked the compressor circuit where it comes through the firewall and I'm getting 48.3 ohms to ground. I can't seem to locate any resistance specs for the stator/clutch...anyone have a clue what they are?

BMcEL

*Update* Just found a short to ground in the compressor circuit. It was grounding on the power steering pump. Works like a champ again. Yeehaw.