1990 gauge swap

[Lou32]

Hello there. 1990 k1500 5.7 auto. Found me a needle type cluster from a 91 to replace the moon gauges in my truck. Same type plug adapter, had to move three wires and boom. Works great. But, as there is always a hitch in my case turned out the tach is for v6 and of course it reads high and nothing at idle. I’m sure this isn’t a new problem, but looking for a remedy if there is one. I would imagine might be a possibility of changing a component inside the cluster, but of course don’t know. As well, I imagine I’d be fantasizing there would be an inline device to place on the tach drive wire to fix the problem. if anyone has input would be appreciated.

You must be registered for see images attach

 

[someotherguy]

I was just reading on the tach issue recently in another forum, let me see if I can find the post. It may be for the 92-94 clusters which electronically are very different, so don't let me get your hopes up unnecessarily.

It's actually very old info that is a bit obscure but the subject was recently revived.

Edit - crap; I was right. His reply was to someone with a '94. I'll go ahead and post it as it may still be somewhat helpful and again, it is pretty obscure info:

To make it read the correct RPM you will need to change capacitor (C103) on the circuit board.
The V6 uses a .0033uf (3300pf), and a V8 uses .002475uf (2475 pf).

I'll ping him in that post on Chevytalk and see if he has the relevant info for the '91 cluster.

Richard

 

[Lou32]

Thank you much. Yeah turns out 88 to 90 are the same but late 90 and early 91 use needle gauges and the same plug for the cluster. Then from late 91 through 94 a different plug

 

[someotherguy]

Thank you much. Yeah turns out 88 to 90 are the same but late 90 and early 91 use needle gauges and the same plug for the cluster. Then from late 91 through 94 a different plug

Depends on who you ask I guess. From experience, 88-90 same, 91 has both moonies and needles depending on the truck, and it's same connector as 88-90 though does require the simple wiring change. 92 is when they changed connector and cluster completely (has the external speed sensor buffer module under the glovebox.) The dash shell had to be slightly changed as well to accommodate the different cluster and connector.

Chevytech says he probably has that info somewhere on the tach change for 88-91 but isn't sure where it is at the moment. It's in a bunch of old material from GM so I suspect he has a lot of it stashed and may be tricky to find.

Richard