I ended up buying a new IVR from Tom's as well as LED replacement bulbs for the lights in the gauge cluster. BTW, the IVR didn't fix it.
Probably logical, since the old one seemed to be doing it's job based on your previous testing.
Best I can tell it's the wire somewhere between the gauge and the unit. I'll have to run a new one I guess.
You still have the dash mounted switch to take into account. They fail almost as often as the sending units.
My bronco was painted red before my ownership and they painted the gauge ring as well which I never really liked. Some of the paint scraped off while I was removing it so I just removed the rest.
Was the dash painted as well? Firewall? You may have to re-ground the body to the dash, and the dash to the cluster. Just to keep bad grounding from being one of the gremlins you have to chase.
Speaking of which, is there still a body ground from the battery to the fender? And what about a body ground from the engine to the firewall? Ford did not see fit to install one of those on Early Broncos, so you might want to add your own just because.
Came out pretty nicely but I had a mishap where I broke one of the new lights and it seems like not all of the lights are on. Though one thing I have now that I've not had in almost 30 years of having my bronco is turn signal indicators!
Maybe the old bulbs were burned out all that time? I had to change multiple bulbs over the years I was driving mine.
The dash bulbs get their ground through the cluster housing, rather than having a dedicated ground circuit for the lamps, like most aftermarket harnesses offer.
Adding LED bulbs can compound issues too sometimes though. They are often (always?) polarity sensitive unlike a regular bulb. So if the housing allows the bulb to go in either way, you should try reversing any bulbs that do not work.
Unfortunately, old sockets fail too, so your literally 50 year old wiring and sockets might be having old-age issues.
I found a yellow with white stripe wire with all of the wires behind the cluster that runs into the large/main loom that runs behind the dash. It has a factory female spade connector. I have no idea where it goes. I don't recall removing it and I've replaced everything else that I can see. Anyone have any ideas?
Yes, that should be the gauge feed to the AUX/Side tank sending unit. Not sure why it would be up in the main dash harness behind the cluster though, as it's for the switch when equipped with two tanks.
However, by '73 they may have integrated it further into the harness, where some were more by themselves. It's not needed up at the gauge cluster, but if that wire is long enough to reach the dash switch, then that's what it's for.
Main tank wire is Orange. Orange from the gauge to the switch, and Orange from the switch to the MAIN/Rear tank sender
Just not sure where these are exactly back there so I'll have to look for pics. It would stand to reason though that this lead not being hooked up could potentially be my gauge issue.
Should not be, as it's for the AUX tank only.
However the switch can still be an issue unless the PO swapped wires. But I think you previously stated that you removed the side tank yourself? If that's the case then maybe we can fix a potential wiring issue. At least temporarily until you need the second tank again.
Follow the Orange wires near the switch and look for two mating 90° connectors. With two tanks this connector is parted and a jumper wire assembly goes to the switch to let you change between tanks.
If you can find the two connector halves that go together, pull them from their associated partners and re-connect them to each other.
This bypasses the dash switch and runs the Orange wire from the rear tank directly to the gauge. Eliminating at least one possible culprit.
See if that gets you anywhere.
Paul
