1968 Barracuda gauge issues

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ns1rm21

ns1rm21

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1968 Barracuda cluster issues
Hello everybody. I have an issue with my Temp and Fuel and I think my Gas gauge. No matter what I do when I turn the key to the run position the needles will slowly peg. I have four different Fuel gauges and when I test them they all do the same thing. I believe the Internal Voltage Regular in the Fuel gauge is not knocking down the voltage to 5 volts that goes to the other gauges. Anybody ever have the same issue?
Thanks in advance. Troy
 
That sounds like the likely cause.
If it was happening on only the gas or temp I would suspect a short on the sending wire to that guage.

Interestingly you said you have other gas guages that are causing the same issue. Unless that are all bad (unlikely) then perhaps there is a bridge between the low voltage side of the cir board and a 12v source.

How are you doing your testing?
 
Are you testing the gauges in the car or on the bench? If in the car, you may have a shorted/grounded circuit board. Assuming it's a bench test and everything is connected properly, the internal regs are probably bad. That's why the aftermarket reg kits are recommended so you don't toast your fuel, oil, and temp gauges.
 
If bench testing be sure to ground the guage cluster /cir board properly


Watch this video

 
cudamark said:
Are you testing the gauges in the car or on the bench? If in the car, you may have a shorted/grounded circuit board. Assuming it's a bench test and everything is connected properly, the internal regs are probably bad. That's why the aftermarket reg kits are recommended so you don't toast your fuel, oil, and temp gauges.
Click to expand...
I have done it both ways, on and off the car. Kinda funny that all four of my fuel gauges would be bad..
 
A few things were left out, but, very good in most aspects. It's hard to cover everything in a 20 minute clip.
 
ns1rm21 said:
In the car with everything hooked up. Volt meter to the feed side of the oil and temp gauge and it’s showing battery voltage.
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That's not good. It should have a fluctuating current that averages out to around 5v.
 
There again, make sure you have a good ground on the cluster housing.
 
I'd isolate the fuel gauge to test the internal regulator. Pull the gauge and bench test it with jumper wires. First test is simply to connect 12V to the input side of the gauge (I connection). Then see what output your getting on the 5V post with a good volt meter. If it's 12V, the regulator is bad. I'd also run a resistance test on the fuel gauge (S for sender) terminal to see if the fuel gauge part is still good. If so, get an external regulator kit and by pass the internal one. If the gauge section is bad too, get a new gauge or have it rebuilt.
 
cudamark said:
I'd isolate the fuel gauge to test the internal regulator. Pull the gauge and bench test it with jumper wires. First test is simply to connect 12V to the input side of the gauge (I connection). Then see what output your getting on the 5V post with a good volt meter. If it's 12V, the regulator is bad. I'd also run a resistance test on the fuel gauge (S for sender) terminal to see if the fuel gauge part is still good. If so, get an external regulator kit and by pass the internal one. If the gauge section is bad too, get a new gauge or have it rebuilt.
Click to expand...
Ok I’ll tray that. If the gauge is out and I put 12 volts to the “I” post then where do I put the ground? The housing is isolated, isn’t it?
 
One lead from the positive side of the battery to the "I" post, the lead from negative side of the battery to a good bare metal connection on the gauge housing. Then connect a volt meter with the negative lead to the same negative gauge/battery connection, and the positive lead to the 5V post to read it's output.
 
Ok…before I forget, thank you for your help.

Out of the 4 fuel gauges I have I have three different outcomes.

Fuel Gauge #1 and 2, the “A” post (feed post to oil and temp) shows battery voltage.

Fuel Gauge #3 the “A” post shows 0 volts

Fuel Gauge #4 the “A” post is interesting. I’m using a Snap On digital volt meter and the voltage is jumping from 0 volts to 12 volts. It’s all over the place. Being this is a mechanical limiter I believe its working however I’m not seeing a constant 5 volts.

You said there is an aftermarket IVR for these…who makes them? Where do I get it?
 
Do a search on here. There should be several threads about it and some links to a supplier. You found out why I don't like using digital volt meters on older vehicles. A good old analog meter will work a lot better.
 
ns1rm21 said:
Fuel Gauge #4 the “A” post is interesting. I’m using a Snap On digital volt meter and the voltage is jumping from 0 volts to 12 volts. It’s all over the place. Being this is a mechanical limiter I believe its working however I’m not seeing a constant 5 volts
Click to expand...
That's what you should expect measuring with a digital guage. If you had a analog meter the needle would be moving around as well. But it would move slower and you could see the approximately 5-6 volts.

The IVR provides a square wave it is either on or off, on it is providing 12v, off it is providing 0v. If it is on 1/2 the time, the average voltage is 6 volts.
 
That is what I am thinking. I’ll replace it in a few hours and I’ll let everybody know what I find. Thanks
 
Make sure the cluster is properly grounded. If not it provides 12v to the guages. The IVR must have a ground to function properly
 
There's an MTSC booklet to go withthe filmstrip. Look through the mymopar collection for 1966 and years close to it for session 227.
Imperialclub's collection has a lot of broken links at this time. :(

First test I suggest is check each gage's resistance.
Gauge Cluster Issues/IVR

If you set up a live test of the IVR on a bench the output voltage will look something like this on a 0 to 8 V scale.
Gauge Cluster Issues/IVR
Scroll up in that thread to see the resistors used to simulate the sending units.

A lot of good info in this thread as well. Redfish knows this stuff.
Bench testing rally gauges
 
Dana67Dart said:
Make sure the cluster is properly grounded. If not it provides 12v to the guages. The IVR must have a ground to function properly
Click to expand...

Im trying to figure out where that gauge gets it’s ground from. The three studs gets mounted to the circuit board so how does the body of the gauge gets its ground from?
 
FD63572D-BE9B-4B7C-A37A-A9D715E19FE1.png
Ok…I just read that the IVR grounds it’s self to the back of the housing..I guess the cluster needs to come back out again and check to make sure it’s grounding to the housing….
 
Same chassis ground path all over these cars. A daisy chain of metal to metal contacts. Internal limiter ground is gauge against unpainted spot in back of housing, then housing to dash, then chassis ground jumper from firewall to engine block ( engine bay near blower motor ). None of the inst' panel will work while its dangling from its harness connectors except the BRAKE warning lamp. Adding a actual ground wire can help lights and everything else work better, plus aids with testing before the panel is fully installed.
On the back of the 3 post gauge, 'I' is input, switched 12V, 'A' is altered or adjusted voltage, 'S' is sender or signal. 2 post gauges use only 'I' and 'S'. The alter was done elsewhere so no post at 'A'.
 
What to let you guys know that I found the problem. I have four fuel sending units. Turns out two of them are good and two of them are bad so I kept getting mixed voltage readings. Once I figured out how to correctly test them (thanks to you guys) I was half way there. Then I found out the gauge was not grounding correctly to the housing. The two tabs were not making good contact in the round, unpainted hole on the back of the gauge housing. Fixed that problem and it seems like everything is now working! Thanks again!
 
If you are trying to measure the IVR output from the fuel gauge with a DVOM you will not get the real picture "Never"!

You need to use an analog meter. Sounds like #4 you tested may be good, but only confirmed with the right meter!

The analog meter will show you 5v pulses most digital meter's will never see!
 
ns1rm21 said:
What to let you guys know that I found the problem. I have four fuel sending units. Turns out two of them are good and two of them are bad so I kept getting mixed voltage readings. Once I figured out how to correctly test them (thanks to you guys) I was half way there. Then I found out the gauge was not grounding correctly to the housing. The two tabs were not making good contact in the round, unpainted hole on the back of the gauge housing. Fixed that problem and it seems like everything is now working! Thanks again!
Click to expand...

Glad you got it! Mopar on!
 
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