Instrument cluster not working?

[Gnmtl72]

When I first bought my truck,(79 J10) all the gauges worked fine but most of the lights were burned out, i took the cluster out and replaced with LED bulbs from Superbright LEDs. When I got ever Put back together, the needles on the dash have been doing funny things ever since, slowly climbing until they are pinned and then staying there mostly. I was told by a couple of people, “Get them damn LEDs out of there they don’t have any business in there.” So I again replaced the bulbs with regular incandescent bulbs. And it didn’t seem to solve the problem. Did I just break the board somehow? Is there something I should check? Can I get both the LEDs and the gauges to work?

[tgreese]

Seems unlikely that the LEDs did this. More likely your "voltage regulator" is not grounded or not connected.

What does the ammeter do? What does the oil pressure gauge do? The fuel gauge and temperature gauge use the "voltage regulator" that's inside the temperature gauge. Improper grounding can make these two gauges peg.

Have you read the TSM? Section 1L in the TSM, free to read and download on the Tom Collins site. Excellent coverage in that section.

TSM.png

Make sure your cluster is properly grounded. There is a ground wire that goes to the flat connector, and the perimeter of the cluster is grounded to the dash through the screws.

You have two posts, but they appear to be duplicates of the same initial post. Welcome from Boston!

[devildog80]

Make sure your cluster is properly grounded......X2.
My '84 GW cluster has all the OEM bulbs in it, but some were not working. Ran a couple more grounds to the body and refreshed the engine ground, and slowly I have bulbs that are starting to work now, that were not before. So ground it better, and put some miles on it.

[will e]

Grounded cluster. x3

[Gnmtl72]

Seems unlikely that the LEDs did this. More likely your "voltage regulator" is not grounded or not connected.

What does the ammeter do? What does the oil pressure gauge do? The fuel gauge and temperature gauge use the "voltage regulator" that's inside the temperature gauge. Improper grounding can make these two gauges peg.

Have you read the TSM? Section 1L in the TSM, free to read and download on the Tom Collins site. Excellent coverage in that section.


TSM.png


Make sure your cluster is properly grounded. There is a ground wire that goes to the flat connector, and the perimeter of the cluster is grounded to the dash through the screws.

You have two posts, but they appear to be duplicates of the same initial post. Welcome from Boston!

Yeah sorry the page froze when I hit submit so I thought it didn’t work, so I did it again and ended up with 2 posts. Thank you for the advice I will start with grounds!

[Gnmtl72]

What does the ammeter do? What does the oil pressure gauge do? The fuel gauge and temperature gauge use the "voltage regulator" that's inside the temperature gauge. Improper grounding can make these two gauges peg.

[Gnmtl72]

Ammeter stays at zero, oil pressure pegs all the way to the right, off of the gauge

[Gnmtl72]

So just to make sure Im understanding you, there’s one wire that grounds the gauges, but the cluster itself has to be screwed in to ground the cluster? I only ask because I don’t want to putbit back together again until I figure out what’s wrong with it, but it sounds like it wont work until it’s screwed in?

[tgreese]

There is a ground wire at pin 4 in the flat connector. Look at page 1L-44. There is a redundant connection to ground through the body steel at the perimeter of the cluster, connecting the circuit board ground trace to the dash via the screws. This is marked GR in the illustration on page 1L-44. Ground is ground, and they are connected to each other in the cluster; pin 4 connects to GR, which screws to the body steel. The body and chassis are one big ground conductor.

In the FSJ, oil pressure, temperature and fuel gauges all depend on the regulated voltage coming from the "constant voltage regulator" CVR inside the temperature gauge. The CVR makes on average about 5 volts for the gauges. With no ground, the CVR does not regulate, and sends full battery voltage to the gauges. This will make them peg, and fail eventually.

The TSM takes your hand and leads you through this, if you read the manual. Page 1L-8 to start.

[Gnmtl72]

I’ve been working on it most if the day and now not only are my gauges still not working but now the lights aren’t either. Checked the ground for the gauge and still not working properly

[devildog80]

Your ground issue is possibly not with the actual cluster, but somewhere else on the truck, on the grounding path back to battery. Make sure the body has good grounds, engine has good ground, firewall to fenders good ground, etc, as the grounding path from cluster to battery goes through what we believe are good grounds between metal body parts, just simply bolted together. With these old trucks, those contact points can get corroded inside the seams where we can't see.
As I said with mine, I thought some of my cluster lights were bad, and all tested good when assembled, but find when driving they do come on. I did have horrible cluster issues with mine as plastic base was turning to dust, had to delicately refurbish it, just to hold the gauges in place and mount solid in the dash. Just need to establish better grounds between components, read through the schematic to make sure all base wiring is right....with grounds x2 or 3 added & verified, then get some miles on it.
The truck will provide you feedback on what it needs, but also needs to be driven and flexed, so everything settles in where it once was. I purposely take mine out on some rough dirt roads driving slow, and go through every pothole, washout, or high/low parts of the road, just to give the suspension and body a chance to flex and settle after sitting for a long time. I have lights that are working now, which were not even after adding grounds, just from exercising the truck over terrain it was designed to be capable of being driven on.
Keep at it, and you will find the method to the madness

[will e]

Im starting to think im not cut out to have this old truck. I’ve been working on it most if the day and now not only are my gauges still not working but now the lights aren’t either. Every thing i try to fix is leading to 3 other things getting worse.

You'll get used to this.

[Gnmtl72]

Yeah, I had a frustrating day but only way out is forward haha. Thank you

[will e]

That's the attitude! Just keep plugging away!

[letank]

the TSM has some very good troubleshooting debugging for the gauges malfunction... I have a copy of the 78 TSM and it is a lot more useful than the 74, which has a bunch of serious errors for the resistance specs.

the short version is to connect a DVM on ohm reading at the connector on top of the oil pressure sender by the right side of the engine and the other end at the battery ground... secure the DVM so the test leads do not end up in the fan, read the display according to engine rpm

[Gnmtl72]

My dad thinks that the LEDs fried the circuit board in the cluster. Is there any way that happened? From what I understand those LEDs are designed to work in old stuff like this.

Chased grounds all day yesterday again. Seemed to work fine and thought I had it fixed, but took it for a drive to test it and oil gauge is pinned again and temp gauge doesn’t seem to be working at all

[will e]

Very unlikely an LED would fry the board unless the LED was super defective and created a dead short. If that was the case your problem would not be intermittent. Installed backwards they simply will not work (diode)

[tgreese]

Well, if you used LEDs that were meant to replace incandescent bulbs, they won't cause any harm. A bare LED (not meant for bulb substitution) must operate in a current range which must not be exceeded. Without a current limiting device (a resistor, or a bunch of LEDs in series) the LED will act like a near-short, burn very bright for a short time and fail open. But shorting a bulb or bulbs won't affect the gauges.

The CVR could have been damaged, but I'm sure the LEDs are not the problem. Can you read the circuit diagram on page 1L-44 of the TSM? Note the schematic is wrong but the drawing is right. There is no connection between pin 5 and the gauges A1, A2, A3. Other than that error, the diagram shows that all the bulbs are in parallel with the CVR and gauges. With LEDs there or not, they won't affect the gauges.

badconnection.png

No connection at the X.

Suggest you follow the diagnostic charts in the TSM. Use your test light and multimeter, and go stepwise through the diagnostic charts.

[devildog80]

Did you replace the oil/temp senders recently?
Are they correct to work with your current gauges, or just got a response at the parts store "this should be the one"? Might need to get more detailed information on the part, and make sure it IS the right one.
I see this a lot over on the CJ forum, with new senders not matching OHMs correctly, to the old gauges.
Just thinkin'....

[ForestG]

Hello all. New to the forum.
"BEAR DOWN" for some nasty weather. Why didn't we stay in Tucson...
Gnmtl72 - I am in the same boat with my '79 J10. We'll get this figured out.