Bad gauges?

[HeroesNeverQuit]

So we ordered all new replacement gauges for a 74 bronco. Originally, the gauges all work. After replacing them, only the voltmeter was working but this was to be expected as new lines were ran.

Originally we thought IVR. Replaced it after testing because it wasn't outputting 5v. Install new one, same problem. Decide to bench test. Ivr is fine. So then we checked each gauge one at a time installed in the cluster as well as the old one.

Oil pressure when installed alone, works. Install water temp? Oil gauge stops working, the water temp works when not installed but then when tightened into the cluster, stops working and no more 5v. It was the same for the fuel gauge.

Now, the old fuel gauge still works and when installed fully the oil pressure still works. My guess is that something in the two new gauges is causing an issue. I'm thinking it's a manufacturer defect since we haven't done anything else to them.

Our old water temp gauge does the same as the new one but we know it was working when originally removed. I dropped it and potentially broke it.

A ground has also been added directly from a good location to the grounding screw at the IVR.

Is it possible we got so unlucky and get two out of four gauges dead on arrival?

 

[Broncobowsher]

The IVR does not put out 5V. It pulses power, maybe once a second. It averages about 5V output. So a little less on than off.
Check that neither post on the gauges has any continuity (a short) to ground. I got a bit lost in the works/doesn't work, but it almost feels like a gauge might have a short to ground on the power side.

 

[Torkman66]

Run a temporary ground from battery ground to back of cluster housing. If everything works then it’s a grounding problem. Easy fix, just ensure a good ground to dash/cluster.

 

[DirtDonk]

The IVR does not put out 5V. It pulses power, maybe once a second. It averages about 5V output. So a little less on than off.

The original style does, but a modern IC style puts out a straight 5 V.
So with new gauges and at least one new IVR, we need to know which type is installed.
Sounds like a new type though, from the sound of it.

And although I haven’t heard of new gauges being as much trouble as some other parts, my feeling is that it’s entirely possible to get two, three, or even four bad new parts at the same time!
Test the ones you have as outlined above.

 

[HeroesNeverQuit]

Run a temporary ground from battery ground to back of cluster housing. If everything works then it’s a grounding problem. Easy fix, just ensure a good ground to dash/cluster.

There's already a good ground run and tested from a good location to a new style voltmeter that then has a secondary run from the back of the voltmeter to the grounding side of the ivr.

Once again, it outputs 5v when the voltmeter and oil pressure are installed. It only stops outputting 5v when the water temp or fuel gauge are installed.

 

[Torkman66]

Hmmm. Then as someone stated, sounds like one of the two gauges are shorting out possibly. Strange.

 

[sprdv1]

Hmmm. Then as someone stated, sounds like one of the two gauges are shorting out possibly. Strange.

electrical sux.. but does sound like that