Here are the schematics of the IP's for a 1979 C/K. They only provide details showing all the components and circuits for the base version. But it appears that the RH side is identical for both the base version and the gauges without tach optional IP. I guess the IP
with a tach would have the tach mounted in the spot normally occupied by the gas gauge in the other versions.
The blue tracing shows the ground circuits. In the case of a base IP there is only one ground circuit that serves all the electrical components in the cluster (other than the seat belt alarm lamp - which for some reason gets it's own dedicated ground)
The red tracers show the components you are having issues with. As noted above, on a base IP there is only one pin on the IP harness that leads to ground and all components are served by a single circuitous conductor.
You will note that your cluster (gauges no tach) has two other pins in the harness that are lead to ground. Their function is noted on the dwgs and doesn't bear repeating.
I think you can see where this is going:
Since you have inspected your IP cluster (connections, pc board, harness clip etc.) and found no obvious problems, I think a grounding issue due to loose/broken wires can be dismissed.
I would start troubleshooting as follows:
Pull the following (one at a time):
The directional flasher relay and the fuse labeled PANEL LIGHTS in the fuse block.
I believe you are cross feeding into the ground circuit of the pc board. This is probably coming in via either:
1. The Gray 8 instrument lighting circuit. This circuit is controlled by the rheostat in the H/L switch (but is protected by the fuse - mentioned above - located "downstream" after the H/L switch). Try turning the instrument lighting voltage all the way down at the rheostat - that would probably confirm that gray 8 as the problem.
2. Another possible path of leakage is from the headlight circuit (all problems disappear when the H'L's are turned off). I don't know whether this problem pops up when
just the headlights are turned on - or do you mean it happens also with just the parking lights energized.
I hope it is when either the parking lights or headlights are on. If it is just when the H/L's are on it will be a head scratcher.
I hope you heeded Viktor's good advice and made sure the bulbs and sockets are clean and have the proper lamps installed.
If one of the steps above temporarily resolves the problem, the next step would be to get the meter out and start checking for voltage where there should be none.
I am having some trouble understanding a certain part of what you mean when you say this:
When my lights are off the turnsignals function normally the rest of the guages function and light up properly no matter what i do.
How do you know that
all the backlighting is working properly with the H/L's off. Without the H'L switch in either parking or headlights position, the instrumentation lighting circuit is dead and proper operation is impossible to observe.
Would it be more accurate to say; The lamps that are giving you trouble (RH side back lighting) are always off. While the lamps on the LH side are functioning properly at all times? Also you aware that there are 3 illuminating lamps on the RH side? I guessed at which two are out - I picked the outer most.
Here are those dwgs I talked about. I am color blind so forgive me if I described the tracings incorrectly:
You must be registered for see images attach
You must be registered for see images attach
My gut feeling is that it will be in the parking/H/L circuit. That somehow it is back feeding to the pc board but not enough to blow the fuse link. The fact that this all started when you hit a bump in the road - and even went away a few times (after hitting other bumps) - tells me that this is going to be a slam dunk fix - when the problem is identified. Intermittent electrical issues that are hidden within the wiring harness can be a bitch to isolate. But they are almost always cheap and easy to repair.
Good luck.
You have checked the ground connection from the instrument panel to the grounding bus block - correct? If not do that. And be sure to check every socket and lamp in the truck (well the outside lights