I wanted to thank everyone for the great advice and support.
I bought the AutoZone replacement switch and borrowed their wheel puller and spring compression tools. The switch replacement went much easier than I
ever would have imagined.
Here are some notes from the experience that might be helpful for other mechanical ‘newbies’:
Ken Burton’s steps on thread “Turn signal replacement” was a great help:
http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=362913&rid=5142&srch=turn+signal
I added these steps to Ken’s instructions:
1. Disconnect engine battery first
2. Mark steering wheel hub and column bolt position to align steering wheel when reinstalling
3. After switch removed, adjust column tilt for greatest clearance through wiring channel
4. Remove new switch connector (had to do it anyway), tape cabling to be as flat as possible, and pull just wires down, then attach original
connector.
The new switch improved functionality but the left turn signal still ran the hazards.
With a known good switch I found the switch connector pin descriptions online. Also using the wire diagrams in the tech manual I was able to trace
each of the leads through the coach.
Pin M, Yellow wire to Left Rear Lamps, was the final culprit.
Ultimately I was able to trace the problem to left rear corner under the bed where the wiring harness ran through a series of 6-pin connectors, linked
with several 2-pin connectors, a tee, and doubled up wires at some connectors. With brittle-bunched-together-46-year-old wires a short was waiting to
happen. For now I clipped the yellow line that was continuing through the backwall channel to the passenger side and found that fixed the last issue.
Besides being very difficult to reach that area I couldn't see why the Yellow Driver side signal wire was needed on the passenger side anyway.
Rewiring the back under the bed will be left as a future major endeavor.
Any way that’s what I did.
Cary
Connector pin-outs:
The new AutoZone SW326 switch wire colors are different from OEM original as well as the connector didn’t fit (too long) nor align with chassis
connector. Unfortunately an adapter wasn’t included in the box.
Found switch wire functions in this YouTube video:
https://www.youtube.com/watch?v=ZmRR0AeZspk
Connectors were molded with pin positions labeled A through P.
AutoZone SW326 wiring (other switches most likely similar):
Posit’n-Color---Function--------------------------Notes
G-------Black---Ground for horn
H-------Lt Blue-Sends Pwr to Lt Frt turn lamps---Lt blue wire also drives dash Lt turn indicator
J-------Blue----Sends Pwr to Rt Frt turn lamps---Blue wire also drives dash Rt turn indicator
K-------Brown---12V Pwr for Hazard function------Should send pwr whether ignition on or not
L-------Purple--12V Pwr for the Turn functions---Should send pwr when ignition on
M-------Yellow--Sends Pwr to Lt Rear lamps-------Yellow and Green also Pwr Brake Lts
N-------Green---Sends Pwr to Rt Rear lamps-------Yellow and Green also Pwr Brake Lts
P-------White---12V Pwr from Brake switch--------Enables turn signals when braking
Turn Switch Testing:
Disconnect connector to only test switch
Put 12V Pwr to the Purple wire (L)
LT Turn lever position should only put pwr to Lt Blue(H) and Yellow(M) wires
RT Turn lever position should only put pwr to Green(N) and Blue(J) wires
Middle lever position should not send pwr to any wire
Put 12V Pwr to the Brown wire (K)
Hazard button should send pwr to (H, M, N, J)
Only test for continuity from Black (G) to horn contact point on switch
--
Cary Lawson
1975 Glenbrook, 455, Rochester carb
Wellington, Ohio
