Speedo /AC Trouble shooting

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Speedo /AC Trouble shooting

Postby ihredneck » Wed Dec 06, 2017 1:20 pm

Been working on putting together a true basket case 1992 W350 G360 4x4.
Got everything figured out except two things.
-AC wont engage
-Speedometer won't work.

As far as the AC I flushed everything, converted to R-134, New expansion valve, accumulator, AC cycle switch (modified to bypass PCM), vacuum pulled and charged. I can hotwire the compressor and it works but it wont otherwise.

For the speedometer, I haven't verified the VSS is working or the gear reducer, but I'm mostly curious does the PCM control this being it is a 92? I have had to bypass it with an external regulator so I know the PCM is bad.
1992 W350 RCLB 5 Speed Locking 3.54s Flatbed completely stock it's whole life (for now) 117K on the clock (In the middle of a frame off restoration)
1992 W350 RCLB Rag Locking 4.10s Flatbed basket case - All the spare parts left from the other W350 & I still have a whole truck left...
1999 RCSB 1500 24v NV5600
2000 VW Jetta TDI
User avatar
ihredneck
fuel screw!!!!
 
Posts: 301
Joined: Thu Oct 04, 2012 9:25 am
Location: Missouri

Re: Speedo /AC Trouble shooting

Postby ihredneck » Mon Jul 09, 2018 9:04 am

Found the issue.

Speedo wasn't working because one of the signal wires from the speed sensor was broke

AC wouldn't engage because of a bad crank sensor. Had tested previously but must have failed sometime. It only would put out 5V regardless of dampener position.

Also, a quick note on the AC. I couldn't figure out how the system worked controls wise. A ground is supplied to the compressor via a body ground. the power is supplied from the AC relay when engaged by the PCM. The PCM knows to engage the relay when it receives a signal from the crank sensor AND a ground from the AC controls in the console that travels through the pressure sensor and AC cycle switch by the passenger fender.

Hope this helps someone.
1992 W350 RCLB 5 Speed Locking 3.54s Flatbed completely stock it's whole life (for now) 117K on the clock (In the middle of a frame off restoration)
1992 W350 RCLB Rag Locking 4.10s Flatbed basket case - All the spare parts left from the other W350 & I still have a whole truck left...
1999 RCSB 1500 24v NV5600
2000 VW Jetta TDI
User avatar
ihredneck
fuel screw!!!!
 
Posts: 301
Joined: Thu Oct 04, 2012 9:25 am
Location: Missouri


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