AC Woes

"Long_Voyager94" (yourenotavalidusername)
07/08/2020 at 10:59 • Filed to: None

Long road here.

Been trying to get my long dead AC system back up and running on my 1994 Voyager.

All the mechanicals are now brand new.

This was the final piece to get the mechanicals done.

They were able to charge the system without a hitch, but they can only engage the AC by jumping the solenoid through the computer, it will not engage via the button on the dash.

They have tested both the high and low pressure switches and they are functioning properly. They have signal coming from the switch on the dash. The ECM however will not send signal to turn on the AC unless they go in manually.

They’re trying another switch and ECM today, but are doubtful it’ll work.

Anyone have any ideas we’re overlooking?

DISCUSSION (14)

jminer > Long_Voyager94
07/08/2020 at 11:07

Seems like you need a toggle under the dash to turn on A/C now.

Nibby > Long_Voyager94
07/08/2020 at 11:11

check the gnomes in the engine bay

Brickman > Long_Voyager94
07/08/2020 at 11:13

C hecked ground and sensor wire from sensors to ECM?

Switches are cool though. ;D

Tripper > Long_Voyager94
07/08/2020 at 11:13

I’m no help here but am in the same boat...Now that I’m dding the M3, the air stopped working... That is what I get for bragging that the air get so cold it hurts.

Going to try a recharge first, but I’m pretty sure its the heater control valve ($200) and not that bad of an install. Beyond that I’d rather not think about it until I have to.

Shift24 > Long_Voyager94
07/08/2020 at 11:17

Man thats one down side of older cars, the A/C systems like to go out, t hrough leaks or weird stupid things

On my 540i it was 2 things, the AUX fan was bad and a temperature sensor in one of the coolant lines. (not the one for the dash but one to tell the AUX fan to kick)

On my K1500 it was the condenser, some thing with sensor/the condenser its self. It would kick the compressor then shut it off.

I am not sure if this helps but I am leaning towards some stupid sensor.

Akio Ohtori - RIP Oppo > Long_Voyager94
07/08/2020 at 11:19

Is there is logic diagram or flow chart available for the AC system ? Sounds like the ECM isn’t getting a signal that it thinks it needs before engaging the AC. First guesses would be something to do with a electronic fan, ignition signal, tach signal, temperature... some failsafe permissive that is locking it out.

When the cruise control on the Disco wouldn’t work I tore the entire system apart and replaced or tested everything. Pump, ECU, vacuum lines. Everything tested ok but the system wouldn’t engage. Turns out I’d replaced the tail lights with LEDs and this was breaking the system’s ability to tell if I was pressing the brakes. Switched the center light back to incandescent and haven’t had a problem.

Long_Voyager94 > jminer
07/08/2020 at 11:38

That is actually one option the shop was thinking. I’d rather it was fixed right, but this may be the route we end up going ultimately.

Long_Voyager94 > Akio Ohtori - RIP Oppo
07/08/2020 at 11:40

He has been digging through wiring diagrams and checking things for 2 days now, so far nothing seems out of place.

But my wiring/ecm are setup for ABS, which my van does not have, so it is possible something is causing issue there without causing issue otherwise.

jminer > Long_Voyager94
07/08/2020 at 11:52

If you wanted the dash button to work you could put a relay under the dash triggered by the button and have that relay send power to the A/C system to trigger it on.

Akio Ohtori - RIP Oppo > Long_Voyager94
07/08/2020 at 12:02

Ugh that sucks. Hopefully the new ECU works :-/

Edit: Oh hey possible there is something about rear air causing problems? Like if it is expecting it or doesn’t have it or the other way around?

Thisismydisplayname > Long_Voyager94
07/08/2020 at 12:10

If the ECM is setup for abs and you don’t have it, are there other changes to that particular ECM that may not jive with the chassis? Can you find a non abs ECM to try? Seems it must be looking for some permissive that isn’t present. Might have to jumper something on the current ECM, but no idea what.

someassemblyrequired > Long_Voyager94
07/08/2020 at 13:32

Some systems have an evap mounted temperature sensor to keep the coils from freezing up - it cycles the compressor off breifly from time to time to keep the coils clear . I fixed a Kia with a similar problem - the ECU was looking for a certain resistance from the sensor corresponding with the coils not being frozen , and the sensor was dead . Just swapped the sensor and good to go...

MM54 > jminer
07/08/2020 at 16:47

This. No reason to get the ECU involved for turning the compressor clutch on, just needs the low pressure switch (for functionality), high pressure switch (for safety), and however you toggle it on (for operability) in series to turn on a relay that powers the clutch . A WOT cutout is a bonus but not entirely necessary, and probably source power from a switched source so you don’t accidentally leave it on overnight and kill the battery :)

MiniGTI - now with XJ6 > Long_Voyager94
07/08/2020 at 21:04

Oh man, well we took our new 1998 SAAB on a 600 mile trip. Had the AC charged on Monday, my SAAB mechanic mentioned it was leaking a little at the checkup on Wednesday and sure enough it only lasted the first day of the trip. 6 hours at 95+ wasn’t great but we made it.

I tried changing it with one of those cans which didn’t seem to work. It later Turned out the low fan resister was also dead so I wasn’t getting correct readings on the pretend gauge on the can. Did I mention it was a holiday weekend so absolutely no chance of getting it in to a pro.

I jumpered between high and low speed so the fan would run on command and then charging from the can worked!

If I fill it right before we leave to come home it might stand a chance of being a reasonably cool ride home.

It’ll be going back to my SAAB guy for leaks and correct charging next week.

Even Scotty Kilmer says you should never use the DIY van lol.