20+ year old GMC 2500?

Geo-TH,In

Well-known Member
Going to look at friends Truck today. He says his turn signals don't work. Also he
says the radio stops playing when he turns the signals on.

It sounds to me there is a problem with the auxiliary power switch. Where is the
switch located???

I plan to locate turn signal fuse and confirm if the switch is bad when it under the
load of the turn signals. He also have a 5th wheel trailer that uses turn signal
power.

I may do a work around and power turn signals with a fuse from battery and remove it
from the auxiliary switch. If the guy turns truck off and can't tell his turn signals
are still on, it's his problem..

So where is the Auxiliary power switch??
 
I think the turn signal works on current passing through it. The grounds are the 4
turn lights. I don't think it getting a good connection in the switch.
I can easily find out with measuring fuse voltage. If it goes to zero, it a bad
switch. Post back later.
 
I'd check for a bad ground in the wiring.

I once had an Olds 88 that started doing bizarre things. Out on the Interstate if you hit the left turn signal to change lanes the cruise would disconnect, etc. Turned out to be a loose ground connection, a sneaky one inside the left fender.
 
Those vintage GMC's are also notorious for bad contact in the main ignition switch connector under the steering column. Lots of signals pass thru that connector. I think maybe 8 pins, mine was yellow, take the cover off and see if wires show melting from overheating. Wiggle connector and see if changes. Good luck.
 
Some of the GM trucks from maybe twenty years ago had ground wires on the frame under the driver's side floor that caused problems.
 
Does anything else quit, or not work-specifically the heater/ac blower? I would believe everything feeds thru the ignition switch, and would start with any connector going to it. A wire around would be the very last resort for me, especially on someone else's vehicle. Mark.
 
Update,
Friend put the flasher back in, charged the battery and all is well.
So weak battery, bad flasher contacts or just moving the switch.
No ground problem. Don't really know the problem, but it's working..
 

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