Gauge cluster trouble

[ls1nova71]

I would try taking out the LEDs and putting in regular bulbs, at least in the front. And run the new ground to the cluster as stated wearlier. The LEDs don't have enough resistance in them and will sometimes make it appear that you have a ground issue.

[magwakeenercew2jh]

Originally Posted by ls1nova71

I would try taking out the LEDs and putting in regular bulbs, at least in the front. And run the new ground to the cluster as stated wearlier. The LEDs don't have enough resistance in them and will sometimes make it appear that you have a ground issue.

Amen!

ABSOLUTELY do everything from easiest to hardest.
And cheapest to most expensive.

In that order!

[bugmasta]

you guys are awesome, i have some work ahead of me. at the office right now, but as soon as i get home will start poking around. thanks in advance!

[bugmasta]

i have 2 extra complete gauge clusters that i have plugged in and tested to see if it was something with the actual cluster. all 3 have exhibited the same results. this tells me that it is not something with the cluster.

since i have multiple clusters i can test it with it in and with it out. no difference either way.

all gauges work when lights are off. turn the lights on the and fuel gauge goes all the way down and the temp gauge goes all the way up.

the dome light does work and i turn the knob to the dome light position. as i turn the switch it also changes how bright or dim the turn indicators glow.

i am going to grab some 1157 bulbs on the way home to test the LED locations.

[71K20chevy]

If the fuel gauge is going down, that means it's getting grounded out, not enough ground...

Dang, you have me stumped

[magwakeenercew2jh]

Originally Posted by bugmasta

i have 2 extra complete gauge clusters that i have plugged in and tested to see if it was something with the actual cluster. all 3 have exhibited the same results. this tells me that it is not something with the cluster.

Right on. The cluster itself is now officially NOT THE CULPRIT. Try the bulbs.

Then, if that's not it...and it would be really cool if it was....we have to look for a relationship between the light switch turned "on" and a grounding anomaly.

I wouldn't completely discount the run between the light switch and the P.C. plug quite yet.

But, let's just hope the LCD's exchange works. Sounds like there's a good chance.

[hayhauler71]

I would disconect the rear lighting harness under the bumper first to see if it is in the front lighting or the rear

[Ed 72 Sierra Grande]

Tuned into this one.

[bugmasta]

sorry guys, got backed up with work and family stuff yesterday and did not get a chance to test things. today should be better with it being friday and all. stay tuned

[TonyJohnson]

Good luck.

[bugmasta]

here is where i am at and what i have done:

-replaced all LEDs with 1157 bulbs: no difference
-cleaned the ground straps and reinstalled: nothing
-replaced flasher unit: nothing
-tested 3 different gauge cluster with all same results
-tested 2 different light switches with same results
-disconnected rear lighting harness: nothing

next step i am going to try is cutting off all the tape from the switch to the gauge plug and see if i can find any bare spots that may be grounding.

[tsali39]

I have a similar problem and appreciate all the input given here.

[bugmasta]

Ok, so I am back to fully functional. I have no idea what it was, but I do know that only my 68 gauge cluster works, but my 2 other cluster, both from 72 trucks, still have the same issues. All I can say is I disconnected the main harness under the hood, blew it out with compressed air, put it back together and the stock gauges are working fine.

I have a brand new set of gauges from a 72 though that still make the turn signals glow and kill all other gauges. Does the 72 use a different circuit board than the 68?

The part that still does not make sense is this originally started with the original gauges installed. It did not start after and changes or modifications. Only thing I can figure is the main harness was loose or dirty and messing with the connection fixed it.

Just seems odd that the 72 gauges won't work but the 68 will. Any ideas?
Posted via Mobile Device

[sduckworth13]

yes.. if one is the "idiot lights" cluster and the other is a gauge cluster then they are wired differently. Look up Vetvette he is my go to guy if I need help with something answered dealing with electrical.

[sduckworth13]

oh just read they are both gauge clusters, Im sure they are wired the same way.

[magwakeenercew2jh]

Originally Posted by bugmasta

Ok, so I am back to fully functional. I have no idea what it was, but I do know that only my 68 gauge cluster works, but my 2 other cluster, both from 72 trucks, still have the same issues. All I can say is I disconnected the main harness under the hood, blew it out with compressed air, put it back together and the stock gauges are working fine.

Just seems odd that the 72 gauges won't work but the 68 will. Any ideas?
Posted via Mobile Device

Great to see a fix happening right before our eyes.

Are you using the same PC for each test?

[bugmasta]

Using a different PC for each test as they are all complete clusters. Is there a way I can test the PC on each of the clusters? The new cluster I have has a factory tach and would really like to use it. But for some reason it has the gremlins in it now and not in my original cluster. The original pics in the thread were of the original cluster. I will take a pic of the new cluster and post it as well.
Posted via Mobile Device

[bugmasta]

Here is my new cluster


Posted via Mobile Device

[magwakeenercew2jh]

Originally Posted by bugmasta

Using a different PC for each test as they are all complete clusters. Is there a way I can test the PC on each of the clusters?
Posted via Mobile Device

You have a set up that works now. So,other than shorting something out and burning up the good parts, and given that you keep everything separate (organized) , it'd be hard to do any harm.

I'd look at the pc that works, matching it up with the others. It's really about the pinning of the plug. If the circuits are the same on each of the pc's, you can test each pc on the good gauge cluster. However, I'd be more apt to test the good pc on the remaining clusters. Or is that what you're suggesting?

Why not?

As for the tach? To make it completely stock, I'd think you need the proper pc, wiring harness, etc. I forget what dizzy you are running. But with your current WORKING set up, I bet you could hook up the stock tach as many have done with after- market tachs. I can attest that is very easy. But I don't have a stock tach,.

[bugmasta]

I have not separated the pc from any of the clusters, just been leaving them all intact. Testing resistance on the new one I noticed that the far left bulb was bad. It was not passing the ground through the lamp. This would then give the indication of a bad ground. I swapped the lamp and will now see if that gives functionality to the new cluster. I now have equal resistance on all lamps and at all grounds. Gonna head to the garage and test it out.
Posted via Mobile Device

[bugmasta]

Well, no such luck. I am getting the same resistance ratings going from the exact same points on the back side of the PC. but when I connect them to the truck, the same gremlins rear their ugly little heads.

Will go after it some more tomorrow when I have more light and can work in the driveway with more room.
Posted via Mobile Device

[slikside]

Originally Posted by sduckworth13

yes.. if one is the "idiot lights" cluster and the other is a gauge cluster then they are wired differently. Look up Vetvette he is my go to guy if I need help with something answered dealing with electrical.

X2! Not to say that you haven't been getting good advise here already, but as I began reading this thread I wondered if he would chime in.

[bugmasta]

here are some readings to share with everyone.

the red line is what seems to be the common ground.

the green line is touching a common ground and then the positive side of each of the lamps

the yellow numbers are the Ohm readings touching the positive and negative side of each lamp. i get the same results at each location also touching the common ground and then the positive side of each lamp.

the 4 numbers at the plug location are the respective numbers coming off the common ground to each of the different pin locations; blue is 2.6, purple is 4.1, black is 5.3, white is 4.8

so i guess in conclusion, what this tells me is that all the circuits are intact and they are all sharing the common ground. the only thing i can think is the common ground is not properly getting grounded to the cab. so, as you can see in the bottom left corner, i have a jumper wire that i am going to run to a known ground on the cab.

if after this, i am at a complete loss. if anyone wants reading from certain points, just let me know and i will test and report back.

[bugmasta]

just sent vetvette a PM. will share with everyone what he reports back.

[bugmasta]

here are some numbers comparing the old gauge that now seems to be working with the new gauge that still has the gremlins. All numbers are from the negative lead touching #7 to each of the other pin locations

Old Gauge numbers

8: 3.0
9: 6.8
10: 3.9
11: 3.8
12: no reading
6: 122.2
5: 78.8
4: 66.0
3: 73.9
2: no reading
1: no reading

new gauges:

8: 2.6
9: 4.1
10: 5.3
11: 4.8
12: no reading
6: 122.9
5: 78.6
4: 66.0
3: 73.5
2: 77.1
1: no reading