Guage cluster acting up, need help.

[TheGreenBarron]

I got a 78 k10 and when i first got it the guages worked fine but on day I hit a pothole and then the speedometer and fuel guage light turned off but still worked and my right side blinker indicator lit up and stayed on whenever i used my turn signal for right turnes it would flash very slowly, but left side is unaffected, also the rest of the other gauges light up and work its just what i mentioned above. The thing with the flasher goes away if i turn my headlamps off. Every now and then when i would get rough roads it would go away but them come back. I took it apart amd cleaned all the connections it didnt help. Any ideas??

 

[Georgeb]

I would find a wiring diagram and look for a loose ground wire. Also check all your exterior bulbs and the grounds for them. I have also found that somtimes the little prongs on the bulb holders for the cluster get bent back. Try gently bending them forward for better contact. It sounds like you have more than one issue causing your symptoms. One with the lamps for the cluster and one with the exterior lamps or a loose connection somewhere.

 

[TheGreenBarron]

I would find a wiring diagram and look for a loose ground wire. Also check all your exterior bulbs and the grounds for them. I have also found that somtimes the little prongs on the bulb holders for the cluster get bent back. Try gently bending them forward for better contact. It sounds like you have more than one issue causing your symptoms. One with the lamps for the cluster and one with the exterior lamps or a loose connection somewhere.

Thanks. All my exterior lamps work its only when i pull my headlamp switch to turn my lights on is when the speedo and fuel guage donot turn on and my right side turn signal indicator stays on and and flashes slowly. When my lights are off the turnsignals function normally the rest of the guages function and light up properly no matter what i do. Ill try bending the contact on the bulbs holders and check the grounds. Could the headlamp switch be the culprit??

 

[yevgenievich]

Thanks. All my exterior lamps work its only when i pull my headlamp switch to turn my lights on is when the speedo and fuel guage donot turn on and my right side turn signal indicator stays on and and flashes slowly. When my lights are off the turnsignals function normally the rest of the guages function and light up properly no matter what i do. Ill try bending the contact on the bulbs holders and check the grounds. Could the headlamp switch be the culprit??

I found a dual filament bulb cause the turn signal issue before. As for others, likely a ground. If some dash lights are working, then that would indicate a working headlight switch

 

[chengny]

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

 

[TheGreenBarron]

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

Thanks for the help!! All the bulbs are good and correct. I need to be clear my guages function whether lights are on or off except if i remember correctly the fuel gauge reads slightly lower as the lights come on but dont quote me on that i have to double check. Of course just the right side doesnt light up and the turn signal indicator stays on when i hit my parking lamps and remains the same when the headlamps come on. I can even dim the the oil, temp and volt guages too as well as the the heater/ac controls amd the courtesy lamp my high bean indicator works as well along with the other light like seat belt warning and 4x4 indicator. Im gonna check the grounds and let you know.

Gonna go through and follow your instructions and let you know. Strange that a pothole caused this mess.

 

[TheGreenBarron]

Well i didnt get to take the dash apart yet but i was toying with the headlamp switch and it seems that when i turn the parking lamps on my fuel guage seems to not read correctly and drops to empty when i dim the lights it slowly goes back to normal but not all the way. Does the same thing when the headlights are on but when i turn them off it goes back to normal the right side tun signal indicator also dims and brightens along with the dimmer. interesting
Ill get in checking those grounds in the morning for now got to go to work

 

[chengny]

I'm telling ya - pull the fuse labeled panel lights and see if that still happens. If not, the problem is with the gray 8 circuit.

 

[TheGreenBarron]

I'm telling ya - pull the fuse labeled panel lights and see if that still happens. If not, the problem is with the gray 8 circuit.

Will be getting up bright and early and doing the things that you outlined above. Cannot thank you enough for the knowledge you have provided ill let you know what the outcome is.

 

[TheGreenBarron]

Problem solved.

So I went through the instructions I was provided above and my problems persisted. I looked at all my exterior lights and grounds and they seemed to be good so I decided to take my dash apart and look at my board one more time to see if there was something I had missed. I removed the cluster and started to look at all the bulb and the tabs on the each socket and came across a problem that I had missed before . the ground circuit was broken on one of the lamp sockets .

You must be registered for see images attach

It was hard to see at first but when I took a small pick and got underneath the copper I could see that it was split so I broke out the soldering iron and put it back together. I plugged the cluster back in and all the symptoms were gone.

I want to thank those that gave me their input and pointed my in the right direction especially Chengny.

 

[chengny]

Good catch - and it makes perfect sense.