65/66 Fuel Gauge VR upgrade?

James Romano

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Hopefully this thread can serve as an official write-up for modifying the internal voltage regulator in the 65-66 C-Body fuel gauge.

I've been trawling the forum looking for a good write-up on changing the fuel/temp gauge VR over to the safer solid state mod. I'm NOT and electrical engineer, so some things I found are beyond my ability, as far as I can tell.

Anyone have a good layman's write-up on doing this mod for the 65/66 instrument cluster?

I found this...
MoPar Instrument Cluster Regulator Update

But again... I'm lost when it comes to all those diodes and stuff. Anything I can just buy and install?

Thanks in advance... Next on the list... head lights on relays and then a hidden stereo.
 
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cbarge

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What car you working on??
Some have the VR integrated with fuel gauge,some are isolated/separate.
 

Mike66Chryslers

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I bought IVR4 solid-state voltage limiter replacements from RT-Engineering. I could have built my own like on the circuit diagram you linked to, but I liked the features that they show for their design.
RTE limiter - rte
 

James Romano

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Yes, the 65/66 design is more complicated. I've read guys making thier own, and all that, but I'm out of my league on that level.
 

Big_John

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The voltage limiter on my 300 was in the low fuel warning relay. Since I added the meter match, I needed to go to an electronic regulator, but I wanted to retain the low fuel warning. The Meter Match had a low fuel light option so all I had to do was figure out the 5 volt regulator.

I ended up using one similar to this : https://smile.amazon.com/KNACRO-Con...90094571&sprefix=12+volt+to+5,aps,190&sr=8-20

71CPxYOUUVL._AC_SL1500_.jpg


These things are all over eBay too... Various prices.
 

Mike66Chryslers

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For a ‘68. But I believe the ‘66 also has the built in regulator in the fuel gauge which means you will have to take the gauge out and disable the original regulator.
Don’t wanna, but need to pull IP to modify regulator
The OP in that thread also purchased their solid state voltage limiter from RT-Eng, the same company that I recommended above. They have a PDF on their website which describes how to use one of their limiters to replace one that was built into the fuel gauge itself.
 

James Romano

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Ok, got out the cluster. Real easy... Took out the Fuel Gauge and holding there.

I read that PDF, but it's for a different set up. I need to look at the schematic as to where and how this get wired into a Fury gauge cluster.

IMG_20200521_192333213.jpg
 

James Romano

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Based on the wiring diagram for a '65 Fury

This looks like how to wire in the IVR3 unit or even the unit Big John posted

layout.jpg


the rest of the install is on the website. Need to open the fuel gauge and bend back the leads on the original VR. I'll post a pic once I do this. Meanwhile, I'm ordering the VR
 

James Romano

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Continuing on...

The fuel gauge is small as is everything in it. Drill out the two black rivets on the bottom of the faceplate (from the back it's a lot easier), it is ok to be a little sloppy here as they are hidden by the bezel, just be careful. I used a 5/64 bit, you can go larger, but not much. Options to reattach the fuel level face plate are epoxy, small screws, or small rivets. Not an issue to permanently seal it as once you perform the surgery inside this thing, it's done for good. You won't be converting it back.

Inside... As you can see, old technology yields fire hazards. It's a copper wrapped bi-metal, point style regulator. And mine is at the point of failure. Charring on wires due to age and heat...never a good thing. All that is needed to be done is to bend the points back away from each other. I will do this and continue once I have the IVR3 in hand.

I chose the IVR3 based on the website and the design of my VR being internal to the fuel gauge. I could have saved some $$$ going with the $6 VR, but I'm not sure it will follow the same design spec and provide the life that the IVR3 will.

Back later this week once the part gets here.

IMG_20200523_114359304.jpg


IMG_20200523_114744062.jpg


IMG_20200523_114905152.jpg
 
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James Romano

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IVR3 came today. Nice little unit. Went right to the install.

First is the mounting. Best place is the ground screw for both lights. This is case grounded, so there is no other spot. The corner where the capacitor was is no good, no clearance.

I slid the IVR3 over the washer so it acted like a shim to give height over the painted circuit board.

IMG_20200527_120852682.jpg


IMG_20200527_120938824.jpg
 

James Romano

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Per the website: inside the fuel gauge... bend one point contact far away from the other, which forces current flow into the soon to be connected IVR3. Close-up the gauge, you're done there. Mount it back into the cluster.

IMG_20200527_115530803.jpg


There is a copper squeeze connector on the terminal marked "A", remove that. You're going to need access to that stud to connect the +5 volt side of the IVR3. You'll need to find a suitable nut to fit on there. I am also doing an Ammeter to Voltmeter swap, so I used the nuts from those studs.

Lock down the gauge, and start the wiring

Ignition goes to +12v side of the Fuel gauge, marked with "I" on the circuit board. It has the male terminal.

The +5v side with the female terminal, goes to the stud marked "A", which feeds the temp gauge.

Use good terminals. Crimp, solder and heat shield everything you do. This is for the long haul and needs to be done right.

IMG_20200527_123735169.jpg
 
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James Romano

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Finished. All hooked up and ready to go. I used screws to secure the face plate. Wiring is as you see it. It's very straight forward and one of those mods that should be on the "must do" list for a 65/66 C-Body. Getting that old style voltage regulator switched over to a new electronic type only reduces the fire threat and adds reliability to your IP.

As a note, I did not have any issues with my gauges. I did this mod specifically because after seeing many other cars with scorching and other issues from the ancient design of the internal regulator, I felt it was a preventative measure to avoid future issues.

I'm very pleased with the outcome and will test it out tomorrow when I get back in the garage.

IMG_20200527_233015686.jpg


IMG_20200527_234051947.jpg
 
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Ripinator

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Finished. All hooked up and ready to go. I used screws to secure the face plate. Wiring is as you see it. It's very straight forward and one of those mods that should be on the "must do" list for a 65/66 C-Body. Getting that old style voltage regulator switched over to a new electronic type only reduces the fire threat and adds reliability to your IP.

As a note, I did not have any issues with my gauges. I did this mod specifically because after seeing many other cars with scorching and other issues from the ancient design of the internal regulator, I felt it was a preventative measure to avoid future issues.

I'm very pleased with the outcome and will test it out tomorrow when I get back in the garage.

View attachment 379435

View attachment 379436

Thanks for doing this "how-to" post. I'm planning to do the same mod on my '66 300.
 

C-440-300

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Big John beat me too it, but, I wanted to update/upgrade. The main point is the current draw. On my '66 C-body, the current for the fuel gauge circuit exceeded the 1 Amp capability of the 7805/317T I was using before, causing a less than ideal response.
I wanted to add my recent 2.5 cents on this. '66 Chrysler fuel gauge inside the column console. I used this circuit from Vintage Chrysler (Allpar.com)
Vintage Chrysler electrical repairs and updates (part 2)
and on a full tank, got above 3/4 full reading.
Then I saw this review:
Efficient DC 12V to 5V conversion for low-power electronics, evaluation of six modules | Arik Yavilevich's blog
and bought this
https://www.amazon.com/gp/product/B00XPZ7I4I/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

If those links don't work, let me know.
Now I get a smidgen over the Full mark for a full tank.
The main issue with the ALLPAR and similar 7805s/equiv is the current draw. It's over 1 Amp. This unit handles 3A, more than enough and with enough margin. Plus, there is no need for heatsink and it draws so little power - way more efficient.
 

mr. fix it

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Big John beat me too it, but, I wanted to update/upgrade. The main point is the current draw. On my '66 C-body, the current for the fuel gauge circuit exceeded the 1 Amp capability of the 7805/317T I was using before, causing a less than ideal response.
I wanted to add my recent 2.5 cents on this. '66 Chrysler fuel gauge inside the column console. I used this circuit from Vintage Chrysler (Allpar.com)
Vintage Chrysler electrical repairs and updates (part 2)
and on a full tank, got above 3/4 full reading.
Then I saw this review:
Efficient DC 12V to 5V conversion for low-power electronics, evaluation of six modules | Arik Yavilevich's blog
and bought this
https://www.amazon.com/gp/product/B00XPZ7I4I/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

If those links don't work, let me know.
Now I get a smidgen over the Full mark for a full tank.
The main issue with the ALLPAR and similar 7805s/equiv is the current draw. It's over 1 Amp. This unit handles 3A, more than enough and with enough margin. Plus, there is no need for heatsink and it draws so little power - way more efficient.

Thanks for the links:thumbsup:

I just ordered a 5 pack(not that I need 5) on a slightly different Amazon link that doesn't have the USB connector soldered onto it already.

https://www.amazon.com/dp/B08Q2YKJ6...bGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==&
 
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