• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Did I just burn out my voltage limiter in the instrument panel?

Kern Dog

Life is full of turns. Build your car to handle.
FBBO Gold Member
Local time
2:57 PM
Joined
Apr 13, 2012
Messages
41,212
Reaction score
155,404
Location
Granite Bay CA
This issue involves THIS car but before I get to that....

000 F.JPG


...I'm building a 1990 roller 360 for my beater 67 Dart. The car sits most of the time so the dead temperature gauge hasn't been an issue but with a fresh engine going in, I want the gauges to work. I remember the old test where you unplug the temp sending unit wire and ground it while a helper looks at the gauge to see if the needle moves.
In the Dart, I grounded the sending unit wire to the negative terminal on the battery and the gauge didn't respond.
Dead gauge or did I burn out the voltage limiter? The fuel gauge hasn't moved in awhile so maybe the voltage limiter was already dead.
In the interest of testing my diagnostic skills on another car, I went over to Jigsaw, the ratty Charger. Same tactic...I pulled the wire from the temp sending unit and ran a wire from it to the battery negative while Rich watched the panel from inside. No movement. In both cases, the ignition was ON but only for a few seconds, maybe 15 to 20 total for each car.
NOW the Charger has no movement at the oil pressure, fuel or temp gauges. Yeah, the ammeter still works!
All the gauges worked before. I mixed and matched the small assortment of gauges I have to get a complete set that worked.
I have several 72-76 A body instrument panels in the attic along with a few Charger and 72-78 pickup units. Do they all use the same voltage limiter?
I remember hearing that newer designs were made that were more reliable. Do you know where to find those?
Of COURSE I ask this right as a 4 day weekend is within reach when all stores are closed but I'd like to get started on this. It would be great if the limiters from other models are interchangeable.
 
FWIW grounding the wire should cause the gauge to peg, full/hot/high... But that said the spec at full/hot/high is 10 ohms... Grounding the wire is zero ohms... If you leave it to long it can take out the IVR or the gauge...
 
I wish that I fully understood that.
If it is grounded and that results in zero ohms, I don't see how that could make a needle move.
Keep in mind that I'm always at a disadvantage understanding electrical stuff.
 
When I run that test, I ground the wire with the ignition off... Then sitting in the drivers seat watching the gauge I switch the key on, when the gauge hits the high end of the scale I switch the key off.... I don't let the gauge needle stay past the high end of the scale...
 
When I run that test, I ground the wire with the ignition off... Then sitting in the drivers seat watching the gauge I switch the key on, when the gauge hits the high end of the scale I switch the key off.... I don't let the gauge needle stay past the high end of the scale...
That is how I did it too. Now I'm gun shy about doing it to the other cars here.


I thought about doing a search for it but had to duck out for a few minutes. Thank you.
 
1747975187137.png


Shoot, man...I must have 10-12 of these in the various clusters I have around here!
 
Actually I don't think grounding the sending unit too long would damage the Voltage limiter rather it would just destroy the gauge. It's possible but not real likely.
See if you have 12Volts to the limiter first if you don't have that then none of the gauges will work just as you've described.
You can easily test the limiter outside the vehicle.
 
Gotta remember Greg that the "gauges" are just volt meters. They get + power from the IVR (when the key is on) and ground via the the sender. Why grounding the sender wire = a full gauge sweep. You sure you grounded it and didn't put the sender wire on the + terminal..
 
Gotta remember Greg that the "gauges" are just volt meters. They get + power from the IVR (when the key is on) and ground via the the sender. Why grounding the sender wire = a full gauge sweep. You sure you grounded it and didn't put the sender wire on the + terminal..
Oh, I readily admit that I struggle with electrical stuff but yeah....I do know the difference between a positive and a negative terminal!

01 A3.jpg
 
It also could be a break in the connections
or blown out on the 'circuit boards' on the back of the gauge panel
the voltage limiter is often the culprit when the Fuel, Oil, Temp, all don't work
if it's just one, it's probably a bad ground or the sending unit for that gauge...

make sure everything's grounded well/properly,
all good clean connections & good ground straps
battery to chassis, fuel tank to body or steel line connection if it's stock,
or motor oil press., water temp senders
even too much Teflon tape or liquid goop can cause grounding issues,
at the senders etc.

good luck
 
Auto Transport Service
Back
Top