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need help troubleshooting '93 a/c

10434 Views 5 Replies 5 Participants Last post by  94PrizmDD
the car has 182k. one day it just stopped blowing cold air. its not hot air, but its nowhere near cool or cold. it seems to blow a little cooler air at night when the outside temperature is not so hot but nothing like "a/c" cold. not sure if that has anything to do with it since im not pulling the outside air in. i figured i should start at recharging it, but i wanted to see if there might be something specific to look at, or get so i do not have to do trial and error so much.

im also going to need some help locating these parts and all that since the a/c units are not my forte.

thanks guys!
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You should be able to get a bottle of refrigerant with compressor oil in it and a handy pressure gauge for a refill on the low side line (left of the intake manifold, right up by the firewall, pretty hard to miss)...this is about $20 at Walmart, R-12 or R-134 whichever you have. If that doesn't do the trick for you, get some leak-test dye and get it in the same low-pressure side, then try to run the AC for a while. If you see fluorescent yellow around anything, you've got a leak...if you don't see anything and you still don't have AC, go get it professionally drained/recharged, should run you ~$100 at a good shop.
Do you hear the compressor kicking in when u turn the ac on? Make sure your a/c fan is turning. Happend to me everything was fine but no cold a/c. Until i replaced the fan. It was such a relief, Miami weather is brutal. Those are free diagnosis. If you got some gauges or a friend with a gauge, see what pressure you have. Im not sure what the correct level is. Im sure someone can help u with that here.
For A/C help from experts, try the forum at Do not add refrigerant without a real gauge set. And never add refrigerant oil without having identified a reason/need (known loss or part replacement) for it. Just like you wouldn't just throw a quart of oil into you engine when it doesn't feel right.

And never add refrigerant with "sealer".

A/C pros call the kits with sealer "death kits" because they'll pretty much ensure your a/c system is dead by the time you're done. And more expensive to fix, to clean out the crap "sealer".
#1 If the green a/c light on your switch is flashing go striaght to #1 If the light does not turn green check the fuses and switch.

Note on checking pressure, the static pressure can be checked on either the low or high side and can be checked with a cheap low side charge kit gage. If any charging is required i highly recomend using a set of gages to keep an eye on the HIGH side pressure. this pressure on the high side should never exceed 400 psi and usualy runs between 150-350 depending on operating temps inside and outside of veh. This can be dangerous and can cuase harm to you or your system. You should also NEVER touch the high side lines( the small diam line) while the system is running as these can become VERY HOT. That being said proceed at your own risk and stop if your not sure what your doing.

2nd thing to do is check the system pressure, check this with the a/c off first, your base pressure should be atleast 50-60 psi depending on how hot the ambiant temp is ( the hotter it is the higher that static pressure should be) 90 outside should = to around 90 psi static pressure, if so go to #1, if however the pressure is low like 10-30 psi or so, go to #2, If your system is empty 0 psi go to #3

#1 Next turn on a/c and look to see if the clutch on the compessor is engaged and spinning at the same speed and the drive pully on the compressor, if its not spinning you need to check the clutch relay ( remove and swap with your horn relay and recheck) Make sure to cycle a/c off and back on, Next check Magnetic clutch and power and grounds at relay. Remove relay and with a circuit tester ( i use a low impendance led test light, all other should be thrown in the trash and should not be used on comuter controled circuits). If you look at the relay it will have 4 prongs, 2 gold 2 silver, the silver side is the control the gold is the load side. match these to the slots in the relay and we will test voltage and grounds here. On the silver side there should be a constant battery voltage on one termial and with the a/c on a ground (signal from a/c amp) on the other side. On the load side (gold) there should be battery voltage on one side and the othe should be a Ground, this is going to the magnetic clutch, if it is grounded and you add power here the compressor should engage if you hear a click when you do this but the clutch doesnt turn the clutch disk is worn out, If there is no ground here you either have an open circuit in the magnet for clutch or in the wiring going to the clutch or the ground side of the clutch. If this is all good go to #4

#2 You have a leak, it may be a small leak or normal system leakage over time. start with one can of freon with oil added might as well get it with the die added as well as this may help find a future leak. Hook up to low service port open valve and start veh and turn on a/c, clutch should come on and may cycle on and off untill low pressure is up high enof. Next check air at vent to see if its cold, if it is you may need to add one more can of freon ( NO OIL or die in this can as this would be too much), check sight glass and stop adding when boubles are gone. and see #6.

#3 STOP, You may have a big leak and may not want to just dump 20-40$ of freon right into the air. You should vacume check your system and check for a leak. IF the vacume does not drop you should next continue with the evacuation for 30 min, this removes any moisture in your system and recharge as stated in #2, if its fixxed see #6. If there is a leak go to #5 or find the leak.

#4 If the pressure is good on the low side and your clutch is engaged check cooling fan and air flow through condensor. Next check the air mix door and cable under the pass side dash( this sometimes comes uncliped and lets hot air from the heater core to enter).If you found the problem see #6. If thats all good you are going to need a set of full gages to read low and high side pressures, you may have a bad expansion valve or a clogged system see #7

#5 I would remove the shrader valve from one of the service ports and get an air gun with a rubber tip and add pressure to the system and stop and listen for an air leak. If you found the leak see # 6. If you cant find the leak see #7

#6 GREAT JOB :clap:

#7 Your gonna need to fork out some cash for help :headbang:
Other things to check could be a bad low pressure switch, bad compressor lock up sensor, open or short circuit in the wiring, bad inputs into the amplifier (ECU) or a bad amp.

Sorry this got so long, someone may wana sticky this as it aplies to most Toyota's
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