AC works, but will not turn on/off inside car

[NISTECH]

ok then never mind, I didnt catch where you said you also swapped the ECM, dont put it in as it would not make it work. If you swap pin 9 with 12 you could at least test the system with the new ECM but you would have massive codes stored for many emissions components that were added in 96.

[maxima278]

I just got done a couple of hours ago testing the other ecm. I did not swap out where different wires go, I wouldn't begin to know where to start with that, but everything seemed to work the same with the exception of the check engine light that would obviously come on because of the new emissions equipment you spoke of. Seemed like it made the car run a little off too. It stunk. Could be my imagination.

My general assumption (and hope) at this point is that the black/purple wire never makes it all the way to the ecm and therefore did not fry it. Wishful thinking? Maybe. If I'm right then can I run a wire straight from the black/purple at the ecm to the black/purple wire at the receiver dryer? According to your diagram I did not see any significant stops between those two points. If you say tell me it might work, I'll try it tommorrow. Still open to suggestions though

[NISTECH]

If you can locate that wire at the ECM at the correct pin number you can simply apply a ground to the terminal while its plugged into the ecm, if it works you know the ecm is not turning it on, the next step would be to start testing inputs to the ecm for the A/C.

[NISTECH]

You know the ambient temp switch is in front of the radiator right? Is it hooked up? If you find it you can try and jump its terminals unplugged and see if that allows it to work.

[maxima278]

ambient temp switch doesn't make a difference. I'm going to try grounding the terminal. I'm not sure what you mean by testing inputs to the ac. You'll have to explain that to me in dumb persons termsthanks

[maxima278]

I used my multi meter to try to trace the black/ purple wire back to the ecu. I noticed there were two of them going into it. one had one short silver stripe incrementally and the other had two short silver stripes. What I found was that I got continuity from the triple pressure switch to the ecu, but that the wire at the switch had the one silver stripe and the one that I got continuity on at the ecm was the one with the double stripe. Is that significant?

[maxima278]

ok, I didn't do it exactly as you told me, I ran a ground from the batttery to where it is jumpered at the triple pressure switch. Is that any different from doing it at the ecm? Anyhow, it still gave me nothing. I'd love to dump it at a repair shop, but I don't know if anyone can get this to work. What the heck have we not tried?

hmm.. if its not the black purple wire, then maybe its one of the wires on the relay that is not getting juiced... I'll have to go back and look to see what color it is, but it would be on the relay opposite from the green wire that goes to the triple pressure switch....

[NISTECH]

If you supplied ground to the black and purple wire at the triple pressure switch with the car running and the triple pressure switch plugged in there is no reason the A/C shouldnt have come on unless the relay is not getting power at the wire coming to the relay.

Do not keep supplying grounds to things or you will fry something. only apply grounds where I say too. If you havent smoked something yet you dont want to.

[maxima278]

I know that. That's why that's the only place I supplied ground to. Which wire at the relay are you talking about?

[NISTECH]

you need to check for power with a volt meter at the blue with orange tracer wire going into terminal 1 of the relay. If there is no power there then you need to check the fuse for that circuit.

[maxima278]

No power on the blue orange wire. currently looking for fuse.

[maxima278]

fuse is ok. what's the difference between the way a 95's ac is controlled and a 96? Can I somehow convert my controlls to work like a 95's if they are that much different? Could it possibly be as simple as rerunning that blue orange wire? If so, I'm ready to test that theory but not until you tell me a safe way to do it. And then if that does the trick then I want to make sure I don't bypass any safety cutoffs or anything.

I would definitely pay someone to do this if I thought it could be done at a reasonable cost. I'm that frustrated.

[NISTECH]

Well heres the deal if you could wire the wire going in the ecm to ground the system will work fine from a saftey stand point of losing freon and blowing out the A/C the problem is it wont cut off when accel is desired and it will drag down the engine, like for example trying to merge on the freeway, It will draw back some of the power. The bigger problem here is you have no power to that relay so that makes it even worse as that is the main source of normal operation. Lets do this back wards then and see if the sytem will work normal, supply the power to that relay terminal #1 and try to operate the A/C normally. This may be your problem[ not having power supplied to that relay] I compared the 2 diagrams for that wire and there is no reason due to the swap that you shouldnt have power on that wire.

[NISTECH]

WAIT I see the problem, on the 96 the power feeds through the main harness then into the engine harness then back into the main harness then back to the engine harness, where as on the 95 the main harness supplies power directly to the same point in the engine harness the 96 eventually does. On of your junction blocks is missing a wire I bet from the main harness as it is the 96 main harness. the wiring diagrams I gave you are for the 96 although all the colors are the same and the diagram is almost identical, there is that one wire that is different. If you power that wire you should solve the problem. as it looks the cooling fans wont come on either when the A/C is turned on.

[NISTECH]

Forgive me if I get confusing here I am a bit tired and am really trying to lay out these harnesses looking at both of them trying to figure out where to correct it. If you add power to terminal 1 of the a/c relay with everything plugged in correctly this should solve your problems. If it does I suggest your add a in line fuse to your power wire and use a 7.5 amp fuse.

[maxima278]

where would you suggest running a power wire from? Obviously something that comes on with the ignition right? You've really worked hard on this. Thanks very much. I'm going to go test this and get back to you.

[NISTECH]

To test the system just go off the battery to jump that wire, set it up in the back side of the relay connector before attaching it to the battery. If the system works tap into the #1 terminal for the fuel pump relay. obviously tap into the wire on the back side of the relay socket of the fuel pump relay.

[maxima278]

I don't understand why but it did not work. what does the other side need to make that relay work? Could we be missing a ground somewhere?

[NISTECH]

tonight when I get home from work I will lay out the diagrams and go over ever wire to try to determine why this isnt working. Acouple things you can do is check the triple pressure switch with it uplugged make sure the switch is closed[you have continuity between the 2 terminals in the switch]. if that checks out remove the relay and set your meter to volts scale and check terminal 2 [the one going to the ecm] watch it as you turn the A/C on see if it locks on a voltage. It will be a zero voltage but it will lock and not flutter around 0 volts. What happens with volt meters at 0 volts is the tend to jump around when the see nothing for continuity like it will bounce 0.00v then 0.01 volts sometimes up to 0.02 volts or -0.01 volts. you are looking for it to stop fluttering and lock into a setting like 0.02v or something like that. This will tell you the ecm is grounding the circuit. DO NOT use your ohm setting to test this,thats not good for the ECM.

[maxima278]

terminal 2, with the ac switch in the on position, shows 4.16 volts and with it off shows .113 or something like that. Not a whole lot of fluttering.

[NISTECH]

That tells me the ECM is switching the circuit. I dont like the way its back feeding 4.16 volts though. ok wire up your voltage to the relay again like you did before, make sure every thing is back together. There is a problem with the wiring and that is why you need to wire up that relay. That problem has been establiched. I cant find anything else in the wire diagram that is different between the 2 yrs.

With that we are going to attempt to diagnose the circuit as if everything is normal. I assume you checked the triple pressure switch for continuity? If so your next step is to find the device in the diagram below. It is usually located on the evap case under the dash near the glove box and has three wires to it. you need to check for 1 power and 2 grounds when the A/C is on. Let me know what your results are. the test is done with it plugged in. you must back probe the wires in their socket, a paper clip or T-pin works well.

[maxima278]

It's funny I've been doing residential electrical work for four years and some of this stuff about the meter has never come up. How do I check for ground? Also if you tried to send me a diagram I didn't get it. Is this device the one that controlls the cycling on and off? My dad kept telling me there should be one, but he has never worked on an AC system newer than the one in his 91 MR2 so I figured the ECM had taken over this duty. I think if you and I get this problem fixed we will have surpassed anything most technicians have to deal with.thanks

[maxima278]

I will perform this test first chance I get tommorrow.

[NISTECH]

ooops sorry about that. here it is.

[NISTECH]

It's funny I've been doing residential electrical work for four years and some of this stuff about the meter has never come up. How do I check for ground? Is this device the one that controlls the cycling on and off?

Thats because AC and DC are 2 different types of electricity. AC is alternating and doesnt have ground persay it has a hot and neutral [both lines are power at 60Hz. DC has a hot and ground and never changes its polarity. To check for ground you do it the same way as you did when you were looking for AC switching. you will see a voltage if its not grounded. We use a power probe to test live electrical circuits, it has a led on it when we hit ground the led lights up green, when we hit power over 6 volts it lights up red.

This device tells the ECM what the evap temp is and prevents the A/C from freezing up. If bad it will not allow the compressor to come on. This is a pretty common problem on newer nissans.

[maxima278]

I have power on the blue orange wire, but the other two do not ground out. They show like .33 on one and .16 on the other and never fully stop jumping around. I didn't see a fuel pump relay in that box. I thought about using the fuse marked audio, but I don't want to fry my new head unit if something goes wrong, so I guess I'll just keep hooking it to the horn fuse and unhooking it when I'm done until we are done with this and then I'll find something to wire it into. So do we need to ground those wires for this to work? If so, then how do we do it properly? If I need to replace that device, let me know and when I am out this evening I'll stop by the place where my parts car is stored and steel the one off of it

[NISTECH]

supply grond to the orange with blue tracer wire while the system is on wire. Dont bother with the yellow wire iut is going to be ground no matter what as it goes through the fan switch to ground. make sure when you do thid the fan is on and the a/c switch is pushed as well as being set to full cold. If this works the thermal amp is no good.

[maxima278]

No such luck. I did as you said and nothing changed. I did however, unhook that device while the car was running and the fans and idle control switched off. so I guess that means the switch is doing its job?? It's not looking good is it?

THe only thing I can think of to do is gut the dash of the parts car and plug it all into the 96 which would be major. As it is I don't believe I even have controll over hot and cold. THe 95 is cable operated and aparently the 96 was not.

Definitely still open to alternatives though.

[NISTECH]

then you must have an ecm issue at this point. the you have just comfirmed the ECM is seeing the signal and attempting to turn it on. problem here lies in the fact the power wire to that relay is different and the ECM is not grounding the relay. The idle increase must be coming from the Iacv rather then the FICD, no matter it probably does that anyhow its just not documented. here is the solution to the problem and it will be a safe one. wire the power up to that relay as we discussed with a fused line. on the wire at the ecm for the ground side of the relay run a wire to near your heater controls and get a cheap 10amp toggle switch on one side of the switch wire to ground the other side will be that wire you ran from the ecm. This is the wire that feeds the triple pressure switch. If the pressure falls out of safe range it will shut down the system. this will keep you from blowing off your freon. Now most important part here label the switch a/c so you know what its for..

[NISTECH]

If I was putting the switch in however I would label the switch "Afterburner" just for the WTF moment from passengers...lol