1988-1994 "Moon" Gauge Compatibility

[FLGS400]

OK my GMT400 gurus, I have a question that I could not find a direct answer to in using the search feature.

My odometer has not worked since I bought my 1991 5.7 Automatic Regular Cab Step Side truck, with the Moon type gauges. I removed the gauge cluster last night and disassembled it. Due to a broken bracket in the trip meter part, it jammed up the odometer, overheated the motor (for the odometer), and burnt the circuit board near the motor. It also appears that this may have also caused a burnt up a capacitor on the board. It seems to me that it would make more sense to swap in a used gauge cluster to replace this one, since many if not all of the broken parts are no longer made new.

My question is, are the 1988-1994 Moon type gauge clusters compatible (like direct swappable)?

I can reuse some parts from mine, like the clear cover piece, or specific gauges if needed. The main receptacle for the wiring harness plug is my main concern. Plus, there seems to be more 92-94 versions of these gauges available at reasonable prices. I don't want to do the cluster conversion with the tach. I have a few Autometer tachometers I could put in if I really felt the need.

If anyone has one they want to sell, I would be interested, too. Just as long as everything works (especially the odometer... LOL).

Thanks in advance for the continued education!

Here's what I'm dealing with:

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[99xcss4]

this might be useful to you

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[99xcss4]

there are also videos on fixing the moonie clusters

 

[FLGS400]

Thanks for posting that video! I was a little confused, as I have seen some moon gauge clusters advertised as for 92-94. Unfortunately, Ebay seems like the best source at this point, unless I can find someone parting out a 91 near me, that still has the gauge cluster in it, or if someone here has one to sell.

I've seen some advertised on FaceBook, but I really don't trust those postings. All of them say "PM me for more information". Those are usually scams.

 

[RacerM95]

I have a 91 Diesel Cluster if that helps

 

[89RCLB]

1991 introduced the rare tach cluster for our trucks and the wiring/connector that the instrument panel plugs into also had some minor wiring changes. Going by the service manual you'll need a 1991 moonie cluster due to the wiring changes (or the rare tach cluster!). Another option is to buy an 88-90 cluster and move several wires around on the connector.

An easy way to confirm whether or not your specific truck was included in the wiring changes is to check for ground on pin B11. Looking at the connecter it will be the bottom row of pins and they count from 1 to 17 right to left. If a pin is populated in B11, you have the 1991 wiring/pin out. No pin populated in B11 and you have the 88-90 wiring.
If the service manual is correct, all 1991 trucks should be pre-wired for a tach. Me, I would double check for ground on B11.

If you go with a 88-90 moonie cluster you'll need to move the following pins around:
A10 to A11
A9 to A10
B11 to B15
Unpin B15 (tach lead) and tape it off or secure it so it can't make contact with anything (or make it available for later if you put an aftermarket tach in).

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[FLGS400]

I have a 91 Diesel Cluster if that helps

I don't think it's compatible... thanks though!

 

[someotherguy]

The damage to the circuit board looks super easy to repair, you can solder a jumper wire across the burnt area. That bad capacitor is no big deal, too.

1991 is a one-year cluster and for a drop-in replacement it would have to be from another 1991. If you luck out and find the rare-ish 1991 needle/tach cluster, you'd want it to be from a truck with same number of cylinders (V6 or V8) for the tach to read correctly.

1988-1990 clusters can be made to work if you move 3 wires around in the harness connector (as 89RCLB mentioned)

Any 1988-1991 replacement cluster you get you'd likely have to recalibrate the speedometer which is done on-board.

IMO you'd probably be better off repairing yours.

People advertising any of these clusters including the years 1992-1994 have no idea what they're talking about and can be safely ignored.

Richard

 

[RacerM95]

Most welcome

 

[someotherguy]

I don't think it's compatible... thanks though!

You could probably use the odometer motor parts from it, though.

Richard