Wiring woes....

[jaked1985]

Soooo, I put a cluster in my k5 today, didn't have one when I got it. Everything hooked up, speedo doesnt work, I can make it work by turning the cable though. Next, when I turn on the blinkers, the amp gauge dips with the signal, the indicators on the dash go back and forth. For instance, lever down for left, left flashes, then right, the left and vice versa with the lever up.....
Im "thinking" ground issue? The right indicator is on full time, all bulbs are new and function..

The cluster I have is from a late 80s, has a light blue plug coming out next to the speedo cable that I have no idea the purpose of. My tub and main wiring harness is from a 79, could this be an issue?

 

[Russell]

The wiring is the same from 78+ so you should be alright there.

Sounds to me like the ground wire is not connected. It is located just behind the headlight switch.

 

[jaked1985]

Thanks Russel, I'll check it out tomorrow. Im pooped! Welded in steering box plates today and did all this dash work. It's quite possible that I missed a ground.

 

[jaked1985]

Update.

I literally traced and checked every wire on the truck to today. No broken wires anywhere. One ground unhooked under the hood.
All the lights work outside of the rig. Inside, the right t.s. indicator is on all the time. When I lift the t.s. lever, left indicator blinks. When I push down on lever, left and right alternate.... Outside... they all appear normal.
Amp gauge still dips with signal blink.
Could it be a bad t.s. switch?

 

[Fordum]

The amp dipping is normal. It just means that you are drawing a load.It sounds like either a miswire or a bad switch.
However, my 77-80 schematics have a note on one of the cluster schematics that says "1979 only" with no explanation as to why,

Also, these guys here know lots more than me about different years, but my schematics are all grouped by a range of years.
Which indicates to me that changes were made.
For instance, they go 73-76,77-80, and 81-87.

 

[blazer74]

An 80's cluster shouldn't have an amp gauge. Went to volt meter at or after 76.

 

[jaked1985]

Aftermarket gauges.

 

[Chevy305]

The plug off the speedo is most likely for cruise control.

Double check your grounds for good contact.

 

[dyeager535]

When did the wiring change on them? I know for a fact the '90-91 is way different, but I'm not certain that is all due to the electric speedometer, that is really only one wire different, yet the printed circuit board is laid out completely differently than say, an '85.

Plug near speedometer is VSS, and would be for cruise *and* ECM if it's an '87-89 cluster.

Someone needs to post a 1979 GM wiring scan compared to say an '89. If they aren't different pinouts, I'll be amazed.

Not to mention, was the '79 idiot lights or guages? Lots of things could have changed.

If I were you, just use a multimeter and check everything. You've just got power, ground, a sending wire for each gauge (except voltmeter of course) then your turn signals, brake light, seat belt, 4WD indicator, high beam, etc., but those are also only one wire on the cluster connector. If those weren't all on the '79 originally, where did the new wires go?