Dash help please

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69conv

69conv

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So my 69 Barracuda has decided to peg the temp gauge and occasionally the gas gauge. I'm thinkin its the instrument voltage regulator either gone bad or has a bad ground. Can someone post a pic of the back of the dash? I'd like to see where its located so I can try to work with it without pulling the dash. Thanks for any help!
 
Found this on this website:
1969 Plymouth Barracuda Restoration
I cant vouch for any of the info.


"Fuel Gauges
While the gauges are interchangeable, the gauge faces use different lettering styles in ’67 - ‘69. So you want to look carefully at what you have, comparing it to the photos.

Original Gauges

The fuel gauge on a ’67-’69 Barracuda is also the instrument voltage regulator. The gas gauge works only if it gets a signal from the sending unit.

(IVR) -- if it fails, the fuel and oil pressure gauges won't work.

The IVR is built into the gas gauge. With the gas gauge open, you can see the little bimetal strip that heats up and cools causing a fast on/off series to make the gauge read correctly.

Rob Robinson - ’68 Fastback

Quick test is to go to the wire where it plugs into the tank and ground it. If it comes up to full it is either the sending unit or your metal strap from the gas line to the sender unit at the tank is missing.

Rob Robinson



If it really is bad this is a great chance to upgrade to the solid state IVR. Here's some good reading on the subject: Vintage Chrysler electrical repairs and updates (part 2). Or you could send it to an instrument restorer.

Josh Walton"
 
If the IVR is bad,then the temp and fuel gauge should wander and bobble in tandem.
In your case I would sooner suspect a bad sender or a problem between the gauge and the block
 
The Cold \______|______/ Liquid Magma gauge......

You need to use a temp gun to figure out where on that gauge is what temp. I still didn't trust the damned thing. 10,000+ worth of engine on a numberless 50 year old temp gauge.

If you plan to use it I'd put a dummy light in somewhere. At least them you'll know when to shut it off.
 
Thanks for the great info guys. I didn't trust the factory gauge either so installed an aftermarket temp gauge. The temp pegs independently from the gas gauge so I'll look at the original sending unit and wiring. Thanks for pointing me in the right direction.
 
You do realize that the IVR is in the gas gauge on you car. The gas gauge has three wires coming out the back, and the temp and oil pressure each only have 2. The IVR in the gas gauge feeds power (about 5 volts) to the gas gauge, oil pressure gauge and temp gauge. If your IVR has failed, none of those gauges will work.
 
69conv said:
I didn't trust the factory gauge either so installed an aftermarket temp gauge. The temp pegs independently from the gas gauge so I'll look at the original sending unit and wiring.
Click to expand...
Very confused. When you asked your original question were you saying the STOCK temp gauge pegs and the STOCK fuel gauge also sometimes does the same thing? later you say you have an aftermarket temp gauge and it independently pegs from the fuel gauge.

Maybe I'm missing something here which gauges are your issues with?
 
Hey Wayne here's pics of mine sitting on the shelf.

20180526_112229.jpg


20180526_112156.jpg
 
Dana67Dart said:
Very confused. When you asked your original question were you saying the STOCK temp gauge pegs and the STOCK fuel gauge also sometimes does the same thing? later you say you have an aftermarket temp gauge and it independently pegs from the fuel gauge.

Maybe I'm missing something here which gauges are your issues with?
Click to expand...

Its the factory temp gauge that's pegging, and doing it independently of the gas gauge. My aftermarket gauge works fine but I don't want to have an electrical issue behind the dash.
 
So armed with my newfound knowledge I ripped apart the dash

dash3.jpg
 
dash7.jpg
Discovered the coil on the right is the one supposed to heat up and break the circuit.
 
I made a power supply using 3 AA batteries and discovered that the coil had lost continuity. A little corrosion removal and the coil is working fine now. Note the gap on the contacts.

dash8.jpg
 
Can you wire up a LM7805 linear regulator and two 10uf caps and eliminate that point contact regulator?
 
IMO the fuel gauge and limiter are close to retirement based on the pics.

Time to start searching for a better factory gauge for stock resto work, or going aftermarket.

I would suggest Charger Specialties to replace them for a decent factory look or if you choose a full custom.
 
Last edited:
4spdragtop said:
Nice documentation! The pic with the gap in the contact, is that with voltage applied?
Thanks for posting Wayne
Click to expand...

Yep, the contacts are open when voltage is applied.

I know there is a solid state regulator available but its too bulky to fit in the housing. I'll have to think of how to do a clean install

RTE limiter - rte

1969383S said:
I would suggest Charger Specialties to replace them for a decent factory look or if you choose a full custom.
Click to expand...

Thanks for the suggestion, I'll look into them.
 
The LM7805 is a three terminal linear regulator. It will fit. Drill a small hole to mount and heatsink. Solder a 10uf 35V cap on the input and output pins. Wire up and you're done.
 
I've used a 7805 regulator on all 3 of my cars and they work just fine. Be sure to use a heat sink though because they do need it. Test the system on the bench before you install it. BTW, it's easier to reinstall the dash with the steering wheel off.
 
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