Need help with Guage Cluster.

[Chadillac]

I'm new here and a newbie to the Bronco world. I have wanted a Bronco for 30 years and finally found the right one.

Need some help with my gauge cluster. I know there is tons of info on this subject but I want to throw this out there because I'm wondering if someone can point me to a starting point. I'm not the greatest with electrical. Basic stuff no problem but when it comes to all the meters and tools like that I'm lost. Plus getting a little overwhelmed with the electrical tech talk. Lol

Here is my situation. My 71 Bronco is 100% stock. I bought it from the original owner so i know it has not been messed with mod wise. Everything has worked until the other day. Well minus the gas Guage. I think that is the switch and that is ordered. The other day I started it up to warm it up and noticed that the temp and oil were pegged out. So I did some searching and found info on the 4 screws that hold gauges to the dash. I loosened them and re tightened and they work! Half way through the day they pegged out again. Tried the screws again and nothing.

Thoughts? I read about this IVR. Bad? Not grounded? I have looked under the dash and everything looks plugged in and not loose. I just need help with a starting point.

Thanks for any help you can offer!!

 

[68stang73]

Sounds like a grounding issue

 

[Pa PITT]

.. MINE HAS NEVER WORKED . SO I'm watching ..

 

[Viperwolf1]

I'm new here and a newbie to the Bronco world. I have wanted a Bronco for 30 years and finally found the right one.

Need some help with my gauge cluster. I know there is tons of info on this subject but I want to throw this out there because I'm wondering if someone can point me to a starting point. I'm not the greatest with electrical. Basic stuff no problem but when it comes to all the meters and tools like that I'm lost. Plus getting a little overwhelmed with the electrical tech talk. Lol

Here is my situation. My 71 Bronco is 100% stock. I bought it from the original owner so i know it has not been messed with mod wise. Everything has worked until the other day. Well minus the gas Guage. I think that is the switch and that is ordered. The other day I started it up to warm it up and noticed that the temp and oil were pegged out. So I did some searching and found info on the 4 screws that hold gauges to the dash. I loosened them and re tightened and they work! Half way through the day they pegged out again. Tried the screws again and nothing.

Thoughts? I read about this IVR. Bad? Not grounded? I have looked under the dash and everything looks plugged in and not loose. I just need help with a starting point.

Thanks for any help you can offer!!

The IVR needs a good ground or the temp, oil and fuel gauges will peg. That ground was originally done through the 4 cluster mounting screws but you could add a ground from the back of the cluster to the firewall or pedal support.

 

[Chadillac]

Ok I see there are 2 wires plugged into the IVR. Are one of them a ground wire or do I need to ground the IVR where it screws to the back of the cluster gauge? I would think one would have to be a power wire and one a ground?

 

[Viperwolf1]

Ok I see there are 2 wires plugged into the IVR. Are one of them a ground wire or do I need to ground the IVR where it screws to the back of the cluster gauge? I would think one would have to be a power wire and one a ground?

Neither wire is a ground. One is 12V going in and the other is variable voltage coming out. The screw is where the ground is.

 

[Chadillac]

That makes sense on the wires. I just ran a ground wire from the screw holding the IVR in place and the gauges are still pegged out. I ran the ground to the frame. Bad IVR?

 

[Rustytruck]

make sure you have a ground wire from the battery to the body and its clean and tight.

 

[Chadillac]

I will try that when I get home tonight. The parts store had an IVR for $40. I might just pick that up and see what happens.

 

[September 1972]

Last night I used a QUICK OT-1 battery terminal and pressed in (2) 4 gauge SAE battery cable ground drops, one to the engine block and the other I snaked around under the fender wiring and brought it up to a fender bolt and with a nut and washer attached it. There was no ground jumper from the engine to frame so the gauge and the rest of the vehicle wiring was searching for the negative of the battery. Since the motor mounts are rubber the circuits look for the throttle to go to the engine lug then to the negative terminal of the battery. The power drop for the vehicle is the 8 or 10 gauge on the battery side of the starter relay.

In addition, the positive terminal of the battery to the starter relay and the starter drop from the starter relay now have OT-1 gauge cable. The gauges we're acting up but the first thing I do is the cables. 8 bucks a foot for the cable and 8 each for the terminals. I hit the starter and it cranked over so fast I thought that the bendix took a dive and the starter was unloaded. The gauges all started to work so I didn't have to cram my fat carcass under the dash which was a relief! Since the gauges run on an average of 5V and the circuit is variable to ground they are sensitive to a weak grounding scheme. As mentioned, the ground to the cluster itself is very sensitive and for reasons unknown on my 68 Camaro, the gauges would not work when I added very good grounds to it ,but started to work when I used the factory setup which appears to be weak. I think that the gauges are sensitive to a ground loop which is in this case, the gauges share a pathway back to the battery with another devise which is 12V.

 

[Viperwolf1]

I will try that when I get home tonight. The parts store had an IVR for $40. I might just pick that up and see what happens.

Pick it up. Your IVR is bad.

 

[Chadillac]

I hope the IVR is bad because that would be a super easy fix. Fingers crossed.

 

[Chadillac]

Update

Well I put in a new IVR. It looks just like the original but has 2 prongs on the power in side. Other than that it is the same look. I installed it and the temp gauge kind of works. It took forever to get to 120 and then fluctuated back and forth 5 degrees. The oil pressure went to 40 and just stayed there.

I took the new one out and put in the original one. All gauges pegged.

So I put the new one in and grounded it. Did the same thing as before. It started to rain and pulled it in the garage and the oil went to 40 but the temp never moved. Lol

So any ideas on where to go from here? Is it by chance the wrong IVR?

 

[Viperwolf1]

Update

Well I put in a new IVR. It looks just like the original but has 2 prongs on the power in side. Other than that it is the same look. I installed it and the temp gauge kind of works. It took forever to get to 120 and then fluctuated back and forth 5 degrees. The oil pressure went to 40 and just stayed there.

I took the new one out and put in the original one. All gauges pegged.

So I put the new one in and grounded it. Did the same thing as before. It started to rain and pulled it in the garage and the oil went to 40 but the temp never moved. Lol

So any ideas on where to go from here? Is it by chance the wrong IVR?

Start by verifying whether or not engine temp stabilizes at 120 degrees. You may have a broken or missing thermostat.

 

[Chadillac]

The stat is only a month or so old. I put a new one in as well as new hoses and flushed the radiator. The temp and oil gauges were working perfect up till the other day and then they just pegged out! My oil pressure has always been at 70 and temp right at 185-190 for the Las 3 months since I bought it. Is 70 a correct pressure or is 40 right? Also with the new IVR in I have run it about 5 times and 2 of those times the temp gauge didn't even move from the bottom but oil is always at 40.

 

[Chadillac]

Just put the old IVR back in and oil and temp peg out. Checked stat and it is good.

This is fun.....NOT!

 

[September 1972]

Solder two wires to a tiny 1W or 2W bulb and put it in series to a sender wire to ground, it should flash, or pulse.

It seems that the gauge cluster ground is wired in series, corrosion might be the culprit under one of the nuts. That's why bench testing is the way to go otherwise it might start to work and you will think it's fixed.

 

[dave67fd]

Oil pressure sounds about right at 40. Should be high when cold and may drop back down at full temp and at idle. Should rise abit back up with RPM rise. Don't assume that the original was working properly as 70's abit high and maybe you are running a little cool.
Confirm you have cleaned the ground mounting area between the IVR and the cluster well.

 

[Chadillac]

I realy believe it has to be a ground since the gauges peg out. I am a little confused by what the new IVR is doing though? No temp and 40 on the oil. Start it up and it goes straight to 40. Warmed up and run up the rpms or even at idle it stays at 40.

 

[September 1972]

If Broncos are the same as mustangs, the gauge polarity is such that grounding sender wire pegs the gauge which isn't good for it, it needs at least 10 ohms.

A wire or crack might be grounding the gauge in the cluster, take a short cut and bench test the cluster, while it's out make a paper funnel over the speedo cable and dump in hot gear oil to lube it.

The IVR is a bi metal relay, heats up breaks the circuit, cools and connects the circuit, that's why there is not a voltage value, it's an average. The IVR needs a good circuit and it's possible that one gauge is soft shorting to the case so bench test it, if you need help we'll show you how to do it. After you fix it and if another issue comes up with it, BAM, you are all over it.

Newer cars with electrical problems are hard, a lot of it is beyond my capacity and I'm not exactly a lightweight. Your problem is babycakes.