AC Trouble Shooting Need Help

[JDMMA70]

So yesterday i charged the AC system after replacing the compressor with a new unit and a new reciever. The compressor would not kick on even after reaching 35psi on the low side. I charged the first can in liquid with the car off through the high side. On my second can after i started the car as stated earlier compressor would not kick on and with my crappy can tap that was leaking a tad bit i jumped the compressor manually cycling it on and off as i charged the rest through the low side. After reaching proper charge level via sight glass, and in car temp reading about 41 degrees at the vents i shut everything off and started trouble shooting. I looked at my pressure switches hoping they werent the problem. I jumped the dual pressure and high pressure switch at seperate times and the ac compressor still wouldnt engage. Check the swtiches with a multimeter they are ok. Moved onto the fuse in the kick panel fuse was good replaced it anyways. Then moved onto the clutch relay behind the battery. It checked out good. I came across this thread while searching for tips.

http://www.supramania.com/forums/sh...-conditioner-electrical-troubleshooting/page2

I noticed Jetjocks post on checking the AC amp and CC. I checked for codes, got an OK via the supermoniter. Turn the AC on no change and no code 51. I checked the ambient sensor in front of the car its within spec. Im at a loss of how to move foward now. I removed the CC from the car to test. Are there any other fuses that i should check before moving foward?

Thanks for your time.

 

[jetjock]

No 51 means either the turn-on signal isn't leaving the CC head (pin 14 on connector D) or the AC amp isn't working. I'm guessing the engine doesn't idle up either. You get a 51 when doing the TPS check right?

 

[JDMMA70]

Phew i was hoping you would find this thread. My engine does not idle up either you are corrrect. I should get Code 51 with the tps unplugged correct?

The CC test outlined in the TSRM says when voltage is applied to the CC Pin 14 should read less than 1 volt with the AC switch on. It measured for me 0.0218~ So im guessing that the switch itself is working. I have a spare CC box that i can take from my other car if i need to test a second one.

 

[jetjock]

Yes, you should get a 51 with the TPS unplugged but it's easier just to press the gas pedal down. If you don't get the code on the SM verify by using the MIL because SM's have been known to lie or not put the system in diag mode.

If pin 14 is low it sounds like the CC head is working. I assume it goes back high when the AC is turned off? If so the problem lies with the wiring or amp. That's assuming you've checked everything on the power side of the clutch circuit.

Edit: Remember, the engine does not have to be running for the clutch to work.

 

[JDMMA70]

Yes, you should get a 51 with the TPS unplugged but it's easier just to press the gas pedal down. If you don't get the code on the SM verify by using the MIL because SM's have been known to lie or not put the system in diag mode.

If pin 14 is low it sounds like the CC head is working. I assume it goes back high when the AC is turned off? If so the problem lies with the wiring or amp. That's assuming you've checked everything on the power side of the clutch circuit.

The clutch relay is getting power but its not flipping it when the switch is turned on. I checked the fuse with a test light and its getting power. Ill recheck the CC head just to be sure. Im gonna admit it but im not good at reading diagrams so when you say clutch circuit im assuming youre refering the clutch relay, pressure switches and etc the stuff i checked already. If i missed something please let me know. The amp looks like a pita to get too cant even see it with the glovebox removed. Im having my father help me with the wiring to see if theres any breaks or shorts.

 

[jetjock]

Yeah, the amp is a pain to get at.

When I said power side I meant all the things you mentioned. The amp needs all its inputs satisfied to send a signal to the ECU for code and idle up. Power and ground must be present, the dual pressure switch must be closed, the coolant over-temp switch not active, and the evap thermistor resistance within limits. If these conditions are met a low from the CC head will cause the amplifier to ground the coil of the clutch relay. Course, the power side of the circuit must also be functional for the clutch to engage.

 

[JDMMA70]

Ok ill get to work on that in the morning. However id like to clarify something. Jumping the pressure switches under these conditions that im dealing with will cause the compressor to still not engage correct assuming that the AC Amp is not doing anything or my CC box is not sending the signal.

I guess this kinda explains why my ac wouldnt turn on after a few months of it not being run. I always thought it was my compressor now its looking like its something electrical.

 

[jetjock]

Jumping the pressure switches won't help if the amp isn't working or not receiving the CC signal. They need to be closed though because they not only supply power to the clutch but also input to the amp.

I'm not sure about something however. Been a long time since I played with this stuff. I'll look into it and post tomorrow.

 

[JDMMA70]

Hey Jetjock, when i woke up this morning and plug the CC back on to the car. The AC button started working randomly. With the key in the ON position i heard the relay clicking on and off when i pressed the button and then all of a sudden the button stopped working again. I unpluged it and plugged it back in worked for a few seconds and now its stopped completely. When the button was working i checked for code 51 and it appeared.

Update: Ok confirmed switches are good, power from the CIG fuse is there. Power from the relay harness end to the ac amp harness end is there. Signal from Pin 14 to Pin 2 on the ac amp is there. That leaves on the CC box or the AC Amp.

 

[jetjock]

Wait, are you saying the button didn't work before? As in didn't light up? If true that's not a minor detail.

Remember, the blower must be on for the amp to function but since you said the 10 amp fuse has power I assume it's working.

It sounds like the CC head or one of the inputs to it eg; the ambient air sensor is flaky. I doubt the amp is bad.

One of the things I'm not sure of and need to check (I have a spare amp here to test) is whether the signal from pin 14 on the box is active low or high. You said yours was 0 volts with the AC on but I remember it as being 12 volts. The TSRM also shows that. In the mean time you might want to try your spare CC head.

 

[jetjock]

Well, it appears the amp needs a ground on pin 2 to operate. This is in conflict with the online TSRM. The 87 book has even more errors.

The amp's logic also prevent idle-up/code generation (as well as clutch operation) if the coolant temp input is low (coolant too hot), if the dual pressure switch is open (refrigerant pressure too high or too low), or if the evap thermistor is open circuited. In short any input that deactivates the clutch will also stop the signal to the engine ECU. I've edited my previous post to reflect this.

 

[JDMMA70]

Ok the spare cc didnt change anything. The other amp made no difference. Dual pressure switch is closed. Ambient sensor is good the one in front of engine bay I hear the relay come on sometimes.

Also jetjock the light for ac on the CC box came on and has always had the abilility to light up. It just the clutch relay sometimes clicks and sometimes it doesnt.

 

[jetjock]

Dunno what to say guy. You have to probe each pin with your meter until you find what's keeping it off. Or you could try this:

1) Unplug both connectors on the CC

2) Supply 12 volts to the 10 amp AC fuse. Easiest way to do that is to remove the nearby heater relay and jumper pins 5 and 4. The two big ones:

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=22

3) Then ground pin 14 on the CC connector. See if the clutch comes on or at least a 51 shows up.

 

[JDMMA70]

im going to check my grounds tomorrow.

 

[JDMMA70]

Jetjock after reading through the EWD i noticed the AC Amp is grounded through the Water Temp Switch which just so happen to be on the Thermo Housing cover. Thinking back i realized that the wiring on those switches have broken before and we mended it the best we could. Knowing that now could my entire problem be those two plugs on the thermostat housing?

Edit

Jetjock my problem seems to have been the water temp switch. I unplugged it and code 51 is thrown relay starts working. So now im wondering why when i plug it in is it not working it must be the wrong sensor for this to happen or bad wiring.

 

[jetjock]

As I stated in post #21 the coolant input to the amplifier can't be low (grounded) or the clutch will be inhibited.

The sensor is nothing more than a single pole normally open switch. With the connector unplugged ohm between the switch and ground. If there's continuity replace it.