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Need Help: 1974 C-10 Instrument Cluster Lighting Problem

DeppvomDienst

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DeppvomDienst Enthusiast

DeppvomDienst

Posted
Posted

Hi:

 

Merry Christmas and a Happy New Year to all you fellow GM truck guys and gals.

 

I have a 1974 C-10 stepside. I am installing coolant temperature and oil pressure gauges where the idiot lights for those same two functions used to be. To do this I had to cut out a good chunk of the cylinder-shaped recesses in the plastic instrument cluster carrier where the idiot lights used to be so that I could put the gauges in there. I decided to leave the "GEN" and "BRAKE" idiot lights alone. They actually fit in well and I thought I was pretty slick doing it that way, but read on.

 

Simply put, now the speedo and heater control head will light but the fuel/oil press/coolant temp gauges will NOT light.

 

I had this problem when I first did the installation a couple of weeks ago. I thought this problem was caused by the absence of the two twist-in idiot light bulbs for coolant and oil on the circut board, causing an interruption in continuity. (I can't re-install them since as I said above, I cut the plastic out to make space for the gauge housings.) I tried bridging this gap on the old ciircut board with a short piece of wire but this just fried the circut board, which cost me the 100 bucks for a new one from LMC Truck. Once I got the new one, I thought that I was back in business but no such luck since I have the identical problem with the new circut board.

 

 

As an aside, I still can't figure how those bulbs have a ground since they just have two contacts that look like they are both positive, in other words, connected in series. The fuses are fine and everything else is working. I am pretty sure the bulbs are all fine but I probably should check that a third time. There very little possibility that I put potentially bad bulbs back in the exact same places, causing a duplication of the problem. Also, in order to get juice to the new gauges I sandwiched the red wires between the contact of a twist-in and the circut board. I grounded the new gauges directly to metal.

 

 

So again, for some reason, the instrument cluster lights on the fuel gauge side as well as my new oil pressure and coolant temp gauges will not light. I will say at this point that original to the truck there are only two big gauges, speedo on LH and fuel on RH with the rest being idiot lights (that only come on during starting) and the lights on the heater control head.

 

 

I know that it is tough to give advice without the truck right in front of ya. Sorry for the long post but I really would greatly appreciate anybody's advice on this.

Thanks,

Depp

  • 1 month later...
John L Enthusiast

John L

Posted
Posted
Hi:

 

Merry Christmas and a Happy New Year to all you fellow GM truck guys and gals.

 

I have a 1974 C-10 stepside. I am installing coolant temperature and oil pressure gauges where the idiot lights for those same two functions used to be. To do this I had to cut out a good chunk of the cylinder-shaped recesses in the plastic instrument cluster carrier where the idiot lights used to be so that I could put the gauges in there. I decided to leave the "GEN" and "BRAKE" idiot lights alone. They actually fit in well and I thought I was pretty slick doing it that way, but read on.

 

Simply put, now the speedo and heater control head will light but the fuel/oil press/coolant temp gauges will NOT light.

 

I had this problem when I first did the installation a couple of weeks ago. I thought this problem was caused by the absence of the two twist-in idiot light bulbs for coolant and oil on the circut board, causing an interruption in continuity. (I can't re-install them since as I said above, I cut the plastic out to make space for the gauge housings.) I tried bridging this gap on the old ciircut board with a short piece of wire but this just fried the circut board, which cost me the 100 bucks for a new one from LMC Truck. Once I got the new one, I thought that I was back in business but no such luck since I have the identical problem with the new circut board.

 

 

As an aside, I still can't figure how those bulbs have a ground since they just have two contacts that look like they are both positive, in other words, connected in series. The fuses are fine and everything else is working. I am pretty sure the bulbs are all fine but I probably should check that a third time. There very little possibility that I put potentially bad bulbs back in the exact same places, causing a duplication of the problem. Also, in order to get juice to the new gauges I sandwiched the red wires between the contact of a twist-in and the circut board. I grounded the new gauges directly to metal.

 

 

So again, for some reason, the instrument cluster lights on the fuel gauge side as well as my new oil pressure and coolant temp gauges will not light. I will say at this point that original to the truck there are only two big gauges, speedo on LH and fuel on RH with the rest being idiot lights (that only come on during starting) and the lights on the heater control head.

 

 

I know that it is tough to give advice without the truck right in front of ya. Sorry for the long post but I really would greatly appreciate anybody's advice on this.

Thanks,

Depp

 

Sorry you're having a problem with those lights. Mine don't light up either and I was hoping someone would have had the "magic bullet answer".

 

Kind regards,

 

John

txab Senior Enthusiast

txab

Posted
Posted
Sorry you're having a problem with those lights. Mine don't light up either and I was hoping someone would have had the "magic bullet answer".

 

Kind regards,

 

John

You the same exact problem as OP? The twist in bulb sockets sometime no longer make adequate contact. You can replace them or clean and maybe bend the contacts a bit. The stick the bulb in.

John L Enthusiast

John L

Posted
Posted
Sorry you're having a problem with those lights. Mine don't light up either and I was hoping someone would have had the "magic bullet answer".

 

Kind regards,

 

John

You the same exact problem as OP? The twist in bulb sockets sometime no longer make adequate contact. You can replace them or clean and maybe bend the contacts a bit. The stick the bulb in.

 

 

Thanks. Yes, the left side of the instrument cluster doesn't light up when the headlights are on. I'll try your hint.

 

You were right on the money when you told me about the dual tank problem. I changed the little filter on the carb yesterday and it runs fine again.

 

kind regards,

 

John

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