New gauge cluster problems

[blakesocia]

So I bought a gauge cluster with tach out of a 77 manual dump truck from Dave on here. My truck is also a 77 but is auto. Tried installing it today and ran into a few snags. Maybe some of you can help me. Everything as far as gauges seem to be working except temp, which I believe is grounding out somewhere, and the tach, which just needs a new plug for the ignition coil. The bigger issue is that none of my cluster lights seems to be working right. For instance the blinkers don't work anymore, but when I press the brake the right blinker dash light comes on. Only thing I can think of is that the circuit doesn't match up to my stock circuit on my old cluster and it's getting confused. Any help would be appreciated!

[blakesocia]

So I figured out that my original cluster was a late 77 model and the new one is a 76- early 77 model. So I know there are a few pins on the harness I need to change. I'm just not sure which ones. Any help out there? Thanks!

[Oberon67]

Sorry, but it sounds like your new gauges are a... cluster.

[ray_mcavoy]

Normally, the difference between the early 76 vs. late 76 & 77 clusters only affects the warning/indicator lights at the bottom of the speedometer & tach. All of the other cluster lights stayed connected to the same pin numbers.

However, the clusters out of the larger medium duty trucks might have some variations that don't always correspond year for year with the pick-up truck clusters. Do both clusters have voltmeters and mechanical oil pressure gauges? If so, they should be compatible but you still might want to follow the traces on the backs of both clusters to see if they match up to the same pin-out or not.

Also check the condition of the tach cluster's flexible printed circuit ... especially the "fingers" in the area where the connector plugs in. If those are tarnished or loose & curled, they might not be making good contact and that could be causing some issues.

[blakesocia]

Yea they both have voltmeter and the mech oil pressure gauges. Would it be possible to use my old printed circuit and just move the new tach and small fuel gauge over to it?

[72blu]

I recently did a similar gauge swap on my 78. I took the tach and small fuel gauge out of the old cluster and put it in my stock one along with the ribbon. It was pretty much plug in and go for me.

http://67-72chevytrucks.com/vboard/s...d.php?t=702346

[blakesocia]

Thanks for the help! I've found some helpful information so far. Would going from a cluster with 4 warning lights (two each under the speedo and fuel gauge) to a cluster with 2 warning lights (one under speedo and one under tach) make a different in the printed circuit or harness?

[ray_mcavoy]

Originally Posted by blakesocia

Yea they both have voltmeter and the mech oil pressure gauges.

Okay, that's a good sign because there were some significant printed circuit / pin-out changes that took place when the electric oil pressure gauges were introduced. And as I'm sure you have already read, you never want to plug a cluster with an ammeter into a truck that's wired for a voltmeter.

Originally Posted by blakesocia

Would it be possible to use my old printed circuit and just move the new tach and small fuel gauge over to it?

It won't be a direct swap, but with some modifications you might be able to make it work. The biggest difference is that the traces on the printed circuit won't be leading to the correct location for the fuel gauge. You might be able to work around that by soldering some wires onto the printed circuit and routing them to the new fuel gauge location.

Originally Posted by blakesocia

Would going from a cluster with 4 warning lights (two each under the speedo and fuel gauge) to a cluster with 2 warning lights (one under speedo and one under tach) make a different in the printed circuit or harness?

Yes, it does make a difference. But it is very minor and only affects the "brake" warning light. In your case, you'd just have to move the tan wire with the white stripe from pin #17 on the cluster plug over to pin #13. All the other wiring should remain the same.

And if you have a 4x4, you loose the spot for the "4 wheel lock" indicator light (which had it's own wired bulb socket and didn't make use of the printed circuit traces).

[MalibuSSwagon]

Originally Posted by blakesocia

Yea they both have voltmeter and the mech oil pressure gauges. Would it be possible to use my old printed circuit and just move the new tach and small fuel gauge over to it?

Yes. I did this on my big truck cluster swap since the printed circuit was in tough shape. I just soldered three short wires to the fuel gauge spots on the circuit and the other ends to the push in metal connectors. It works fine.

[blakesocia]

UPDATE: So I narrowed my problem down to the brake wiring was grounding out my blinkers somehow. I'm not sure how, but I ended up fixing that issue and now my blinkers work fine. Yet when I turn my dash lights on my right dash light blinker comes on solid. When I turn the right blinker on it still blinks tho. Not that big of a deal though because everything is basically working properly.