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I am confused. I still think the system is working normally from that first video.
The ground to turn on AC relay goes: Ground 6 > Blower Switch > AC switch > Thermoswitch > ECU [1E] > ECU [1L] > AC Relay
It seems like your ECU is completing the ground circuit to the relay when you turn on the AC switch.
The relay supplies +12V to the clutch wire. Then your jumper in the pressure switch is allowing +12V to reach the magnetic clutch. Normal to me.
Assuming I have the 94 wiring for AC, I'm no longer wondering why the clutch is engaging with the pressure switch open. The only problem I still have is that the compressor clutch is engaging automatically when the car is on even without the AC switch on. It's not supposed to be doing that, the compressor clutch should not be engaging without the AC switch on. The only time it operates normally is if I have the pressure switch jumped, so it should operate normally with the system charged and the pressure switch connected. My concern with that is if it all leaks out again and I have nothing in the system, the compressor clutch would still engage and get damaged. Without the jumper in the pressure switch connector (simulating too low of a charge), the compressor clutch should be disengaging, not staying engaged like it is.
Originally Posted by alexdimen
It seems like your ECU is completing the ground circuit to the relay when you turn on the AC switch.
The ECU is completing the ground circuit to the relay when it's not supposed to, whether the AC switch is turned on or not. That is the problem.
Originally Posted by alexdimen
The relay supplies +12V to the clutch wire. Then your jumper in the pressure switch is allowing +12V to reach the magnetic clutch. Normal to me.
Correct, and that is normal, with that jumper in there (simulating a charged system), that's the ONLY time it operates normally. However, with the system empty, that's simulated by removing the jumper wire, the compressor clutch should not be engaged, and yet it is, and that would damage the compressor. The pressure switch is there as a safety measure for the compressor, and the ECU is basically bypassing that safety measure and telling the AC to run no matter what.
On an unrelated note, my buddy with the other 94 said he has floating voltage (about 2v when it should be 0v with the AC switch on) on terminal 1E at the ECU, due to the blower motor and fan speed switch sharing a ground, and it would randomly turn his AC on and off. I checked and I saw 2v floating voltage too (although I don't remember having the on/off issue), so per his suggestion I pulled the ground wire for the fan speed switch out of the connector (going into the resistor pack on the blower) and grounded that separately. I'm down to 0.9v now. Still not perfect, but better. But like I said, it's unrelated to the current issue.
Ok i was wrong the pressure switch is on the clutch side of the circuit on the 93 only. On 94 It's one of the switches that gives a ground to 1E.
Still the pressure switch and AC switch are in series to complete the same input ground to the ECU on a 94. How could the AC switch trigger the ECU output on and off and the pressure switch doesn't? I came remember...Have you checked to see if 1E is grounded out somehow?
Correct. Sometimes I wonder if I actually have the 94 wiring harness since they seemed to put MANA and Denso systems in cars with no rhyme or reason lol. But being that the clutch is getting power regardless of whether the pressure switch is simulated closed, I guess it stands to reason. Either way, the switch should still have to be closed for it to come on. So the AC switch triggers the output only when the pressure switch is simulated closed. Other than that, I have no idea if it's having any effect on the system whatsoever. Kinda makes me wonder about the AC switch though, that's something I haven't checked. Maybe it's fried and stays closed. The light isn't on unless the switch is pushed though, not sure if that would be an indication of what it's doing or not. Although if it had a short that kept it closed, it should be constantly on if the pressure switch connector is jumped, too.
I did check 1E and if I remember right it was grounded once the car is turned on but not any time other than that. That was one of the things I checked earlier because it made sense that would be the case.
I looked for new adapter fittings today but I couldn't find any that would work for me. I did notice when I removed the old ones that the high side one wasn't completely tight, I was able to remove it by hand.
Chris told me to switch the output to a different terminal in the connector, and I changed it on the tune also and the compressor doesn't come on anymore at all, even with the switch jumped. But Chris sent me a map with the changes so I'm going to load that one tomorrow to make sure it's right. I have the system on vacuum right now and I'm going to charge it tomorrow also.
Damn, that is weird. 30 posts in and I finally understand your problem and haven't really helped find a solution
Well I still appreciate your help, it's not like I've figured it out either lol. It is certainly a weird problem, and it's more difficult to track when you're not here to see it. I just hope I figure it out someday lol.
Did you check to see if the magnetic clutch is grounding out? It may be as simple as a bad or about to go bad magnet coil.
If it's grounding out, that would cause it to be on constantly, correct? Because this one can be disengaged a couple different ways. If I remove the AC relay, or if I jump the pressure switch connector to indicate a charged system, the clutch will disengage. And by jumping the connector, everything works normally and the clutch engages with the AC switch and disengages with it off. But if the pressure switch isn't connected and if the connector isn't jumped, the compressor runs as soon as I start the car.
However, since swapping it to another output on the ECU connector, it's not running at all now. But I have to use Chris's map first, I haven't tried that yet. The only thing I've tried since swapping the output is the changes I made in the map regarding that. Maybe Chris did something different. Either way, we're pretty sure it's coming from the ECU.
I have it on a vacuum right now, I'm going to charge it and check for leaks and proper operation after this.
I just tried the new map from Chris and I still have the same problem. So it's either something outside the ECU causing this, or maybe a mechanical problem inside the ECU.
Busy day. Chris remoted in and looked into my issue today. He said the issue seems to be within the ECU, but it's actually acting normally. I asked if there was an issue with the wiring in the AC system that I caused and he said no. The only problem is we don't understand why it wasn't doing it before.
These are with the key on to accessory, but not with the car on. The first pic is with the pressure switch connector jumped, and the second pic is with the jumper removed. With the jumper, it sees 5v and keeps the switch off, but without the jumper the voltage drops and provides a ground.
by https://www.flickr.com/photos/159205146@N07/, on Flickr
I charged the system and did it incorrectly lol. But it still charged, and the AC is working properly with a good charge, as expected. I am wondering though if the switch will shut off the compressor if it gets overcharged. Last time I charged it until the compressor shut off and then bled off some until it turned back on. But with the system being all jacked up I'm afraid it won't work. Also, I had less than a can and a half to fill it with and I ended up disconnecting them before they were empty, so I'm sure it's not full anyway. I did add about another 1.5oz of oil just in case. Here is the screen with the AC charged and the car on. Obviously the first two are with it off, then on, but I don't remember the circumstances of the third pic lol.
by https://www.flickr.com/photos/159205146@N07/, on Flickr
I used UV glasses and light to check for leaks and didn't see anything. I'm looking for a sniffer but I don't really want to buy one and I'm not sure if the parts stores rent them. Autozone only had the light and glasses in a big kit along with the pack off the shelf I already bought.
Chris said he's going to look into it more to see if there is a way around this issue, and we can talk to Syvecs about it if he can't get it and see if they can add another option. He suggested I change the wire over to a terminal with a 5v pullup, but it didn't work. However, I moved the output wire instead of the input wire lol, but he said it wouldn't have worked anyway.
Well, I guess I screwed the pooch on this one. When I was charging the system the other day, I opened both low and high side. That's what I was talking about when I said I messed up, but I was too embarassed to mention it lol. I should've brushed up on the process but I thought I remembered. My gauges haven't read anything close to accurate when trying to add more refrigerant or just checking the system with the car running. Now I think I overcharged the system trying to get them to read correctly, because the compressor won't shut down now at all, no matter what I do. I even jumped the connector and it was still running. So since it's acting like it did before (for the most part) when the system was empty, I'm guessing it's again outside the range of the switch. When I removed the high side fitting, darkened (burned I guess) ester oil came out. For now I just bypassed the compressor, I'm tired of messing with it.
I borrowed a new ECU from a buddy in Texas and it's acting the same way my ECU does, so maybe the problem isn't in the ECU. This past winter I replaced the compressor again (I rebuilt an original one from a friend's car), swapped in a new condenser, flushed the whole system including the evaporator, and replaced the expansion valve and all o-rings.
As soon as I start the car, the compressor clutch engages without AC or anything turned on, and this is with the system not charged. I haven't tried jumping the pressure switch connector again.
Maybe there is some kind of failed sensor or switch? IDK, I'm so fed up with this.
This is one of those dumb electrical problems that you have to be methodical about.
I think the AC compressor gets 12v from the wire going to it to engage the AC. Get the shop manual and Body Electrical Manual and start going through the parts. I know there's the pressure switch under the battery, the switch on the evaporator behind the glove box, and the AC button/fan switch itself. You also have the ECU that can cut out the signal at high load/RPM. And the relay. Something is stuck in the system. Could be the relay?
Should be easy to test with the engine off, you can just put a meter on the wire to the AC compressor and go through things until you find what kills the 12v to it.
Yeah it gets 12v from that wire, but I'm not sure how or why that wire is getting power all the time. Another problem is I need to figure out first which wiring diagram I need to follow, because they operate a bit differently. I assume it's the 94/95 since mine is a 94, but I believe we determined sometime a while back that it's acting like the 93 wiring. It's almost like several different components failed all at once, but that's so unlikely. From our past troubleshooting it also seemed unlikely that it wouldn't be the ECU itself, but both of them are doing the same thing, so unless I wrecked the new ECU somehow, it has to be something else. I changed the map to where the AC wouldn't come on at all just to verify it's a mechanical problem and the clutch still engaged.
The really strange part is what it did when I jumped the connector to bypass the switch. Just to refresh, the clutch will engage automatically when the car is started, and even if the pressure switch is disconnected, it will somehow still get 12v to engage. The only way to disengage the clutch is to jump the connector to bypass the pressure switch, which is exactly opposite of the way it should be. Now the weird part is that when I jumped that connector, the engine bogged down as if AC kicked on, but the clutch disengaged.
Odd indeed. It's almost as if the unit is getting conflicting signals; pressure switch activation vs. compressor clutch engagement. I was going to suggest a different compressor altogether but it appears you've already done that approach.
Is it practical to temporarily reconnect a stock ECU to determine if the same phenomena occurs? In doing so, it may allow you to focus on the various A/C components & connections that Dale has mentioned above wout worrying about the ECU side of things. Alternately, it may lead you to the Syvecs setup being the culprit.
The Syvecs harness is completely different than the stock harness. Although I could swap in the stock harness and try to find a stock ECU, and that would at least tell if me if it was something outside that engine harness and ECUs. I guess I could temporarily run wires from the ECU to the engine bay AC components to verify if it's that part of the stock wiring.
I would agree with you if it wasn't working properly during the summer of 2019 lol. And boy did it blow cold. That's not to say that something inside the ECU or it's wiring hasn't gone bad since then. Although I'd think if it was in the ECU, swapping in the new ECU would have fixed it.
What do you mean pull the ECU out? You mean swap in a stock one? Add a meter on the chassis harness that wraps around the front of the car? And what wire specifically do you mean? Or just all the applicable wires?
I think you're going to have to go back to the basics to troubleshoot this. Start by hooking up a voltmeter between the 1 pin connector that brings +12VDC to the compressor and ground. Measure the voltage you see there with the engine off, key in the ACC position & RUN position, but don't start the car - should be 0V in all of those cases. Now start the car, but keep the A/C switch and blower fan switch off - should still be 0V. Now turn on the A/C switch, but keep the blower switch OFF - yup, should still be 0V. Next, with car running & A/C switch still ON, turn on the blower fan & cycle thru all 4 of the blower speeds - you should now be seeing +12V at the compressor at all blower speeds, presuming you got enough refrigerant in the system to not trigger the pressure switch OFF, and the evaporator core hasn't froze over yet, which would trigger the thermal switch cut-off switch. Here's a schematic & description of how the stock system works from the '94 Body Electric FSM
I don't think I've ever seen that page, condensed into one pic. I like that, thanks!
I can try all that, although my system isn't charged at all and it's still coming on. But I'll still go through the steps as if it's charged. It'll still allow me to trace back to where the power is coming from.
Looking at the wiring diagram again, I should probably also clarify that the blower motor isn't coming on unless I engage the fan switch, and the radiator fans don't come on unless I push the AC button. So those two things operate normally. It's just the compressor clutch engaging when it isn't supposed to that's the problem.
I put the multimeter on the wire to the compressor to check for voltage.
Key to accessory - 0v
Running but no AC - 14v
Running with AC - 14v
I also tested with the pressure switch disconnected and the wire to the switch jumped.
Disconnected - 14v
Jumped - 0v
So it confirms the way the compressor has been acting. I pulled the AC fuse in the relay box and it killed voltage to it as well. I want to pull the AC relay but I need to remove the bumper to do that where I have the box mounted, so I'll do that another day. I checked the pressure switch and it's open, which I suppose is normal since there is no pressure. The wiring diagram shows it closed, but I guess that's indicating the system is operating, IDK. I'm going to pull that out and use compressed air to see if it closes.
I think I'm on the right track now. After talking it over with my buddy that's a 7 owner and professional mechanic, we stumbled on what we think is going on. And considering I discovered this problem a couple years ago and forgot about it lol, I'm pretty sure this is it. I didn't think it through while looking at the wiring diagram back then, but it makes sense now. First I had to determine if I had the 93 or 94 wiring. My car is an early 94, so I figured it could be either one. But I determined it's for sure 94 wiring, first by the colors of the wires, but also by verifying that the wiring from the pressure switch doesn't go directly to the compressor like in the 93 wiring.
by https://www.flickr.com/photos/159205146@N07/, on Flickr
The red line is grounding out automatically, which would explain why the change of ECUs didn't affect it. It's bypassing the ECU altogether and providing a ground for the relay and sending power to the compressor. I was going through old emails with Chris Ludwig and noticed that two years ago I determined it was only grounding after starting the car, and while that makes sense with regard to the compressor clutch only getting power once the car is started, I'm trying to figure out WHY it's only after the car starts. If the wire is making contact with the chassis, it should have continuity with ground even with the car off. So I'm wondering if that wire is making contact with another wire that gets ground only when the car is started. I pulled that wire from the connector at the ECU (1L in the stock ECU connector) and it's not getting ground with the key on, but I'll test again tomorrow to verify it's happening with the car running.
Now to the pressure switch. With the switch connected OR disconnected, power still gets to the compressor clutch because the wire from the AC relay to 1L at the ECU is already grounded, thus bypassing this part of the circuit completely. This would make sense because the switch is apparently open if the system is undercharged or overcharged (it was open when I tested it the other night, as there is no pressure in the system), so the circuit is incomplete in both instances. If I jump the wires together (the yellow line), bypassing the switch, it completes the circuit and the system acts normally, the same way it would if the system is charged and the switch is closed. Jumping the wires with the system discharged (or overcharged) kills the power to the clutch, while the system being charged and the switch closed gives power to the clutch like normal. I'm still not sure I understand why jumping the wires kills the power to the clutch when the system is discharged, but my buddy understands why and it seems to be the case either way.
Now I just need to figure out what is supplying ground to the AC relay.
I checked for continuity to ground from that wire 1L with the key off and got 5 kiloohms, but as soon as I turned the key to on and start, I got no continuity at all.
by https://www.flickr.com/photos/159205146@N07/, on Flickr
Now for the weird part. I had removed the leads and when I put them back on, I put the black lead on the wire and the red lead on the ground, and it read full continuity with the car running. Then I swapped the leads back to red on the wire and black on ground and I got no continuity again. Ugh.
With that wire disconnected from the ECU still, I checked for power to the compressor clutch and got 0.012v. So that means that wire must not be grounding to the chassis or anywhere else.
by https://www.flickr.com/photos/159205146@N07/, on Flickr
Then I checked to see if the ECU was providing the ground. I disconnected the wire to the stock connector to isolate it just in case, and put a needle lead through the back into the ECU. I got 121 ohms. Not crazy high, but enough I guess. Then I jumped the pressure switch connector and lost continuity, until I turned on the fans and AC button and got continuity back, 121 ohms again.
by https://www.flickr.com/photos/159205146@N07/, on Flickr
So maybe it's the ECU afterall? Although the new ECU didn't change anything, so maybe it's the map? I thought maybe it was the thermoswitch since it's the only other thing in line before the ECU, but all that does is complete the circuit or not.
"1. Disconnect the ECU and check for continuity to ground and voltage on ECU connector 1E with the key on and the blower switch in all positions and AC switch on and off. The GY/R wire.
2. With the ECU disconnected, check for continuity to ground on ECU connector 1L with the key on and off. The Y/B wire.
Those two tests will tell me if it's in the chassis or the ECU. I think we had some issues with the fan relays when I had the car. I can see where one of the relays, if faulty, could backfeed positive voltage into the sensor circuits all the time and cause an always on condition. Let me know what you find."
For these tests I just disconnected the two wires from the Syvecs connector, but all the other connectors and wires were plugged in.
I ran the tests the first time but didn't have the 15a fuse in the relay box, but I put the fuse back in and tested everything again and got the same results. For the test on 1E, continuity to ground, I got open on all settings (with the fans on and the AC on and off). For voltage, I got .005v on all fan speeds with the AC off, and .003v with the fans on and AC on.
For 1L with no fuse, key on and continuity to ground, I got no continuity, and with the key off was the same, no continuity. I put the 15a fuse back in and checked this again, and got no continuity with the key off but with the key on I got continuity with ground. I had the black lead on the wire and the red lead on the ground. I swapped them, and got no continuity. I swapped them back and got continuity again.
I might borrow a Fluke from work and check this again tomorrow.
Chris filled me in a little more in my language on how it works haha, so I did some testing again.
"The AC button and the fan speed switch are both in the 1E circuit. The AC button just opens and closes the circuit. The fan speed button will close to ground in the off position and close to positive voltage when it’s in the 1-4 positions. It pulls to 12v but has the resistors to create variable voltage for each speed. But we set the ECU up to turn the AC on when it sees any voltage. So, with the AC button on and the fan speed off, you should continuity to ground. With AC button on and fan speed at 1-4 there should be 3-4v. With the AC button off it should be an open circuit. "
I tested again with my multimeter just to verify, and I got the same results.
AC button on and fan speed off, open circuit.
AC button off, open circuit.
AC button on and fan speed on, no voltage.
I tried something else too though. 1E disconnected and 1L connected, I get 14v to the compressor. So the ECU is getting no voltage to tell it to provide a ground, and it's still providing a ground to the relay.
With 1L disconnected, I get no voltage to the compressor. So that means it's not grounding out anywhere, and it also means the AC relay isn't stuck closed.
I was still confused about not getting voltage on 1E though, then I remembered. The system isn't charged, so the pressure switch is open and not providing voltage. I jumped the pressure switch and got different results.
Whether the AC button is pressed or not, it sees full 14v with the fan speed off. With the AC button on and fan speed one I get 1.6v, fan speed two I get 2.7v, fan speed 3 I get 3.3v, and fan speed 4 actually dropped down to 3.1v. So if Chris is correct, I still have an issue with it getting 14v instead of continuity to ground with the AC button on and the fan speed off. Then again, jumping the pressure switch connector makes the system operate normally, or so it seems.
05-01-20, 10:24 AM
Well I still appreciate your help, it's not like I've figured it out either lol. It is certainly a weird problem, and it's more difficult to track when you're not here to see it. I just hope I figure it out someday lol.
