Gauge Cluster Issues/IVR

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Bronze Barracuda

Bronze Barracuda

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I have my dash apart on my 68 barracuda I am testing for continuity between circuits on the PCB. I have hooked an alligator clip up to the positive on the oil pressure gauge and then grounded the pins leading to the negative of each gauge oil, temp, fuel. The temp and fuel gauge sweep but the oil gauge does nothing. I have also tested the gauges out of the cluster But still cannot get the oil gauge to sweep? I guess it is busted?
But the main questions I have (see pictures) is how do the oil temp and fuel gauge get a positive feed? from the looks of the circuit they all are connected via a common circuit.
(In one of the pictures I have an alligator clip hooked up to the positive terminal of the oil gauge) you can see the circuit connects all three gauges positive terminals, but where do they get power from? Is there a positive wire that hooks up to one of the terminals?
Also in the picture I have a red pointer that is pointing to the positive of the temp gauge the last terminal is the fuel gauge. Why does the fuel gauge have three terminals and what is that black wire for that leads to (a condenser?)

Finally I cannot find Instrument Voltage Regulator did all cars have a IVR ?

Thanks Everyone

Barracuda Guage Cluster.jpeg


Gauge Cluster with Clip.jpeg
 
The common between the 3 guages is the 5-6v positive feed from the IVR in the fuel guage. The output is the post with the black cover. )Not the one the capacitor is attached to. That one is the 12v feed.
There should be about 10 to 12 ohms between the posts on the guages.
 
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Dana67Dart said:
The common between the 3 guages is the 5-6v positive feed from the I've in the fuel guage. The output is the post with the black cover. )Not the one the capacitor is attached to. That one is the 12v feed.
There should be about 10 to 12 ohms between the posts on the guages.
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OK I am going back out to shop I'll tackle this with a little more knowledge now thanks.
PS what about the oil gauge ya think it's pooched? Can they be repaired?
 
Mike69cuda said:
The ivr is built into fuel gauge. Lots of threads about it on here.
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OK I now know the IVR is in the fuel gauge I was watching a video some guy posted on youtube he had a valiant.
Some are just mounted on the cluster. I guess some clusters were a bit cramped , so they stuck it inside the fuel gauge?
L
Searching how to upgrade IVR and how to open up gauges.


:thumbsup:
 
Check out post 15
Bench testing rally gauges

Use the photo to test the guages. Ohm meter between sender and 5v common posts should give 10 to 12 ohms for each guage. (Update, I measured my 70 guages again and got 11.6 and 14.4 I opened one of them and it was like new inside) you don't get that the guage is internally broken. O ohms = shorted, anything much higher than 12 ohms (from others it indicate it appears that 20ish would be a good Max) anything much over that would indicate a bad connection.

If you open up a guage you might get lucky and only needs a connection reattached. But if the heater wire is toast or the bimetal is toast I would be looking for a replacement.
 
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All 3 of these thermal gauges are 20 ohm gauges. Check fuel gauge at posts A and S. Check oil and temp gauges at posts I and S ( they dont have a post at A ).
The limiter is chassis grounded via a slither of metal on the back of the gauge against a unpainted spot in the housing. test different ways on the fuel gauge. you should find the 20 ohm gauge, a 50 ohm limiter and a combined 70 ohms.
i'm guessing your oil gauge is bad but... did you kill it. 12 volts will kill them. The 5 volts at zero resistance will too after a few minutes. Senders stop at 10 ohms. So when the wire would get knocked off the oil sender and short to zero resistance ground on the engine the gauge would peg, eventually overheat, and die. Good luck with it.
 
RedFish said:
All 3 of these thermal gauges are 20 ohm gauges. Check fuel gauge at posts A and S. Check oil and temp gauges at posts I and S ( they dont have a post at A ).
The limiter is chassis grounded via a slither of metal on the back of the gauge against a unpainted spot in the housing. test different ways on the fuel gauge. you should find the 20 ohm gauge, a 50 ohm limiter and a combined 70 ohms.
i'm guessing your oil gauge is bad but... did you kill it. 12 volts will kill them. The 5 volts at zero resistance will too after a few minutes. Senders stop at 10 ohms. So when the wire would get knocked off the oil sender and short to zero resistance ground on the engine the gauge would peg, eventually overheat, and die. Good luck with it.
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Hey thanks.
It was dead all along. I removed the cover for the oil pressure gauge and took some pictures, have a look. This is all 100% new to me
 
Bronze Barracuda said:
Hey thanks.
It was dead all along. I removed the cover for the oil pressure gauge and took some pictures, have a look. This is all 100% new to me
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Whoops I accidentally hit send before I was ready.
Anyway take a look at the pictures, it seems like one of the wires must have burned off at the end of one of the wraps around the bi-metal.
I tested the 3 gauges I had a zero reading on the oil gauge that's why I took that one apart. I figured it's already giving me grief so what the heck why not punish it with a little inexperience.
The other 2 gauges temp and fuel read 20.6 ohms and 20.8 ohms. Is there anyone that can repair this type of gauge? Or can you buy areplacement gauge?

IMG_20200223_163542.jpg


IMG_20200223_163609.jpg


IMG_20200223_163814.jpg
 
Mike69cuda said:
If you post a want ad I’m sure you will find one here on the site.
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Yep I will give that a shot, but first I would like to try and repair. I am a shocked at how basic these things are. I'll probably need to find someone with good eyesight and nimble fingers
 
Yes there are 13 ohm fuel gauges in later models. Thats all though. Temp gauge in that panel is still a 20 ohm gauge. I don't know why you're seeing 11 ohms there.
 
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Bronze Barracuda said:
Whoops I accidentally hit send before I was ready.
Anyway take a look at the pictures, it seems like one of the wires must have burned off at the end of one of the wraps around the bi-metal.
I tested the 3 gauges I had a zero reading on the oil gauge that's why I took that one apart. I figured it's already giving me grief so what the heck why not punish it with a little inexperience.
The other 2 gauges temp and fuel read 20.6 ohms and 20.8 ohms. Is there anyone that can repair this type of gauge? Or can you buy areplacement gauge?

View attachment 1715475987

View attachment 1715475988

View attachment 1715475989
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I repaired them for about 8 years. Offered exchange service for these fuel gauges with a solid state IVR designed specifically for this application. I retired.
The bimetal strip should be arrow straight at room temperature. Overheated enough to retain a bow is scrapped. We can't just straighten it and expect it to respond properly to temperature changes.
New replacement gauges are out there but I dont know if sold individually.
 
RedFish said:
I repaired them for about 8 years. Offered exchange service for these fuel gauges with a solid state IVR designed specifically for this application. I retired.
The bimetal strip should be arrow straight at room temperature. Overheated enough to retain a bow is scrapped. We can't just straighten it and expect it to respond properly to temperature changes.
New replacement gauges are out there but I dont know if sold individually.
Click to expand...
I suppose ya couldn't be sweet talked out of retirement for one last time, just for reminisce.
 
I just resistance checked the three gages from my 67 Barracuda.
Each one was 20 ohms.
In operation; the fuel gage worked, the temperature reads low, and the oil pressure seems high.
Measurements in the engine bay had indicated to me the IVR output might be seeming resistance.
So even though the circuit board looks pretty good, before removing the gages a resistance check in the line was in order.
upload_2020-2-24_19-34-31.png

Using probes tips on the board itself shows it to have no resistance.
So one issue must be the oxidation on the studs and PAL nuts.

I don't know if this may be applicable but seemed like it might be.
 
RedFish said:
The limiter is chassis grounded via a slither of metal on the back of the gauge against a unpainted spot in the housing. test different ways on the fuel gauge. you should find the 20 ohm gauge, a 50 ohm limiter and a combined 70 ohms.
Click to expand...
I [now] understand this grounding contact.
upload_2020-2-24_19-44-33.png

The brass sheet retained in the tabs touches what looks like gray. Do I need to look more closely at that?
upload_2020-2-24_19-47-33.png


edit: fixed! Thanks Mike69cuda!
 
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Mike69cuda said:
Is that gray in the pic an unpainted corroded housing metal?
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Oh yes you're right. It must be the zinc/pot metal casting and the off-white must be a finish.

upload_2020-2-24_20-24-29.png

This is what happens to the ole brain late in day.
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The off white may be to help diffuse the instrument lighting.

And I bet you're right that its pretty oxidized.
 
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