Gauges randomly drop to zero

[subforry]

Hello all,

I installed and RTE IVR3 and after about 15 to 30 min driving the gauges drop to zero, then move back to their correct position. This continues randomly. Overall the car has corrosion issues in the electrical. The gauges didn't work when I got the car. I think this was caused by a 12v source problem, maybe corrosion in the fuse box. I bench tested the original voltage limiter and it seemed to work ok. To be safe I installed the IVR3 and disabled the factory limiter by bending the contact arm. Installed a new fuse, the old one was 10amp.

Has anyone seen this behavior with an IVR3?

I expect there is a voltage source problem maybe at the fuse box or the ignition switch.

Any ideas?

Thanks

 

[pnora]

Easiest thing you can do is rig a test lead and monitor the power to the regulator. If that works ok you can do the same with the ground. If they both check out ok its most likely a defective regulator. Adding an extra ground might be a good first step.

 

[QuickBpBp]

Sounds like it's losing a ground.. Make sure that battery terminals are tight it could be that simple..

 

[RedBeard]

Agree, most likely a bad connection/ground.

 

[subforry]

Thanks. Seems like some add a specific ground wire to the cluster. I will also connect a volt meter to the 12v source to see if anything is happening there.

 

[subforry]

BTW this turns out to be a temperature thing. When the dash is hot from being in the sun the regulator doesn't work.

 

[pnora]

BTW this turns out to be a temperature thing. When the dash is hot from being in the sun the regulator doesn't work.

What have you done to test things when this is happening?

 

[subforry]

What have you done to test things when this is happening?

I connected a test light 12v input on the back of the IVR3 and drove the car for many times. The bulb was lit when car was running. The gauges consistently failed after the car was parked in the sun.

 

[pnora]

I connected a test light 12v input on the back of the IVR3 and drove the car for many times. The bulb was lit when car was running. The gauges consistently failed after the car was parked in the sun.

Did you verify 12 volts was there when the gauges failed? Did you verify the ground was present when the gauges failed?

 

[twecomm]

Think you not only need to verify that that you have a solid and continuous +12 V battery voltage on the input to the regulator, but verify you are seeing the 5 volt output from the regulator, as that 5 volts output is what is the voltage source for the gauges. All the senders for fuel, temp and oil pressure simply are connected between chassis ground and one side of the gauges and provide a variable resistance with function. The other terminal of those mentioned gauges is fed by the IVR3 regulator output which is about 5 volts. The IVR regulators mimic the factory regulator in that when you first apply the 12 volts to the regulator via the ignition switch, the regulator puts out a full 12 volts to the gauges for a few seconds, the it falls back to 5 volts DC. This function gets the gauges to read quickly since they are all thermal devices in the way they work. In the mentioned gauges, a coil of special wire is wound around what is basically a bi metal strip that is heated by the current flow thru the variable resistance of the senders. Depending on current flow thru the coil, the gauge strip heats and bends to physically move the needles. The alternator gauge is different. It has an internal "shunt bar" that the battery / alternator current bidirectionally flows thru which creates a magnetic field in the shunt bar. That magnetic field created by current flow thru the shunt bar deflects a small magnet which is part of the the needle assy. to indicate which direction the current flows thru the shunt, charge or discharge of the battery. Good luck with it, at least it works somewhat so you will eventually find the problem. Could be a bad regulator..

 

[JimKueneman]

OR it is doing what it is suppose to and detecting a high current and shutting down till it detects the short is gone. It could be the coating on one the gauges nichrome wire is flaking off and touching the metal bimetallic strip causing a temporary short.

 

[subforry]

OR it is doing what it is suppose to and detecting a high current and shutting down till it detects the short is gone. It could be the coating on one the gauges nichrome wire is flaking off and touching the metal bimetallic strip causing a temporary short.

Yep, I think this is what is going on.

After much more testing, in and out of the car. There is definitely high load or short on the 5v side. I am still confused about why it works in the morning and fails in the afternoon.

I will try pulling the 5v input to the temp and oil gauges. I should be able to narrow it down to what gauge. But what am I looking for in the gauge?

I have bent the bimetallic arm of the factory voltage regulator. It has viable blackening where wire wraps around the arm. Is the wire wrapped around the arm energized with 12v when the contacts are closed? I am asking because these parts are still in the circuit.

Thanks.

 

[JimKueneman]

Yes the 12V is applied to that coil and it heats up until the bimetallic strip pops the other way and the circuit opens and removes the 12V from the gauges. Then it cools and the strip snaps back and closes the points and applies 12V to the gauges again. That is the old regulator.

The gauges works the same way except the sending units are in series with the gauge coil. When 12V is applied the sending unit limits the current so it only heats the wire coil so much and the bimetallic strip just bends so far and it’s hooked to the needle moving it. If the insulation is flaking off the coil and it is shorting to bimetallic strip it will over current the regulator. It could be the gauge need to move to a particular place before the coil wires contacts the bimetallic strip.

 

[Skatpak]

Todd with Todds Restorations I specialize in the repair/restoration of these gauges, clocks, power pack, hl motors, and other parts specific to the first Gen I have posted pics of my work on this site, just search for skatpak, I'm on Facebook Todds Restorations and also my other page is 66-67 Charger freaks, if you want to call me to discuss the problem your having and possible causes I'm happy to talk to 6ou about it, if repair is necessary I can help you with that as well, Todd 763-290-0474. It is much more effective and time saving to talk on the phone vs trying to message this back and fourth. I work from 9am to 12 to 1am 7 days a week, so I'm available to take calls during these hours,