89 240sx; Strange s13 Relay problem with AC and headlights...

[NISTECH]

I went through the manual I downloaded and the way it is layed out is much different then the factory service manual but still workable. I need you to do something though match the wire colors with the terminal layout you have of the connector as the manual does not define which terminal is what in the socket. With the wire colors I can figure out what goes where. I will say this though ,according to the measurements you got it doesnt seem correct. There should not be any terminals side by side with voltage. You have it posted that terminals 1 and 2 both have battery voltage. That does not appear to be correct. As those 2 terminals should be opposing sides of the circuit. Terminal 3 has me curious as to why it has a resistance reading . If you had both the campressor and fan disconnected it to should read open circuit.

[comablack783]

Ok I opened the back of the relay box and this is what I found, here are the terminal numbers as I had them listed with the Wire colors.

|[1] [2]||[3] [4]|-----------[5]| |[6]

#) Main color/ stripe color1) Blue / Orange2) Black/ White3) Blue/ Green4) Brown / White5) Green/ Light Green6) Blue / Orange (same as 1, but thinner cable)

Hope that helps.

[NISTECH]

Sorry man didnt mean to leave ya hangin. I will mill over the diagrams at my earliest convienance and post back.

But I need to know is the fuse blowing with the fan and compressor unplugged but the relay installed?

[comablack783]

Ok, with the relay in, the fuse does not seem to blow, but the compressor wont kick on. with the fan unplugged and the relay in it doesnt blow, with the compressor unplugged and the relay in the fuse does not blow, with both the fan and the compressor unplugged and the relay in the fuse does not blow.

-Jumper

with the jumper in, fan and compressor plugged in, the fuse blows the minute the key is turned. with the jumper in and the compressor unplugged, the fan plugged, it blows the fuse. with the jumper in, the fan unplugged, and the ac compressor connected the fuse "blows" *... It didnt blow imediately though, the AC actually turned on and I started playing with the settings, the second i went over 2 it took the fuse(what does this mean?).

[NISTECH]

Does it blow the fuse with the jumper in and both unplugged? If it does you may have a shorted FICD valve. If you can unplug that and plug the fan and compressor back in jumper it and see if it wont blow the fuse. If it doesnt then your FICD is the problem. It too is on that circuit off the relay.

[comablack783]

no, it does not blow the fuse with the jumper unplugged. with no relay or jumper the fuse does not blow. with no relay or jumper, ac and electric fan unplugged the fuse does not blow. maybe what ever is making the fuse blow has to do with that jumper set up. in either case its not supposed to run with a jumper so lets assume thats a problem right there, with the relay the fuse doesnt blow, but the compressor wont kick on? so the question is why wont the compressor work with the relay?

[NISTECH]

Well technically I was asking if it blew with the jumper INSTALLED but the compressor and fan UNPLUGGED. In any case yes the problem is it wont turn on the compressor any way. So this means the ECM is not grounding the relay or the ECM ground signal is not making it to the relay. There is likely a pressure switch between the ECM and the relay, I am going to have a look at your wiring and see if I cant find that pressure switch. On your car that switch is located on the receiver/dryer.

EDIT: Ok forget the pressure switch for now its not set up the same as newer systems but keep it in mind as it may be part of the control problem.

Heres what you need to do to determine if the circuits will function normally with the realy in and you playing the part of the ECM. Supply a ground to the green with yellow tracer wire from under the A/C relay with it installed in its socket. You are going to jumper that wire to ground fromt the bottom of the relay socket. All A/C components should come on at that point. I suspect it will blow the fuse since all the relay really does is jumper 2 circuits when the ECM grounds the 3rd circuit in that relay. At that point I think you primary concern is why the circuit keeps blowing fuses. At that point why the ECM isnt turning it on isnt really relevant as the circuit wont work if it did. It will be easier to figure out why it wont trigger the relay once the integrity of the other 2 circuits arent comprimised.

[comablack783]

Ok, I got around to doing the tests today. with a fuse in, relay in, and the grounded jumper connected to the green with yellow tracer wire behind the relay box, the fuse did NOT blow. AC kicked on and it was nice and cold. does this mean that something is wrong with my ECM? does it mean that the ECM ground isnt making it all the way to the relay like you said? or maybe its that wire

Here is a pic of what i did

[NISTECH]

No it doesnt mean the signal to ground the relay isnt making it. It may not even be sending a ground signal. If all the conditions are not satisfied for the ecm to determine that it can send a signal it wont send it. Now you need to test all the inputs to the ECM that it uses to determine that. One is that pressure switch I was talking about. If that switch is open the ecm wont turn on the A/C. If the thermister in your Evap core does not close it will not turn it on. Lastly if it does not see the request for it to come on it wont turn the A/C on, that would be the fan swicth AND the A/C switch.

Also You need to chuck that test light at the earliest convience. The ONLY thing that is good for is checking fuses. Never use it to check electronic circuits. You could fry your ECM if you havent already fried that driver during your testing, that would be one expensive fuse to blow.

[comablack783]

opps, didnt know that tester could do so much damage, i was just using it for a ground lol..

"Now you need to test all the inputs to the ECM that it uses to determine that. One is that pressure switch I was talking about. If that switch is open the ecm wont turn on the A/C. If the thermister in your Evap core does not close it will not turn it on. Lastly if it does not see the request for it to come on it wont turn the A/C on, that would be the fan swicth AND the A/C switch."

How do I go about testing these components? also i wanted to tell you t that my brother has the exact same car (an 89 coupe) with working AC, and hes offered to lend me any part that could be swapped out for possible testing on my car. note that when i used the grounded jumper the compressor wouldnt turn off, doesnt mater what the control box is set to the compressor is always running. I would like to get to the bottom of this problem and have proper working AC, but if thats not possible i wouldnt mind settling for a temp rig. would it be safe and possible to run a grounded jumper, with a switch to the interior that allows me to turn on the jumper so i can have AC when i want it, and turn it off when i dont need it? just a thought anyway.

[NISTECH]

I have to decipher the wiring from the down loaded manual for the sensors/switches to test. Not much you can swap since you would loose freon trying. Only the A/C control head can be swapped without loosing freon. Do not run your A/C with a rigged jumper. If the system over pressurizes it will blow your freon out from the pop off valve.

[comablack783]

ok cool, sorry havent been able to get on since florida was pounded by wilma, just got my electricty back ... let me know what test to run... i feel were getting closer to solving this problem..

[NISTECH]

Bumping up for myself. I didnt forget about ya. need to take some time to look through your wiring in that manual. Not easy to read as it isnt layed out very well. I will post when I have a test for you.

[NISTECH]

Heres what you need to try. Locate the dual pressure switch, shoul be on or near the reciever/dryer. unplg the connector and jump the wires. Make sure your whole system is all together when you do this test and have the A/C turned on with the car running. See if it comes on. If it does you are either low on freon or that switch is bad. If it still doesnt come on you will need to suply a ground to the thermister/termal amp that is loacted on your heater box. there is three wires on it you need to supply the ground to only one of the wires and you can not add the ground tot he wrong one or you could fry a control unit. you will need to asses which one by checking the terminals with a volt meter for power. 2 of the terminals should have power and 1 wont. That one is the one you need to supply a ground to. If you dont find a power on 2 of the wires dont attempt to ground any of them and post back to let me know.

[comablack783]

I havent forgotten about this, hopefully ill have some time this weekend to run these tests. by the way do i have to remove my dash to reach any of these things i.e. the pressure switch, heater box, dryer?

[NISTECH]

no you can access the pressure switch it is near your radiator on the reciever/dryer. You may need to remove your glove box to gain access to the thermal amp.