1966 Belvedere II - gauge issue

I replaced my headlamp switch to fix an issue with my dash lights not working, and as long as I pulled my dash out I ordered I also replaced my voltage regulator, becuase my fuel gauge was not reading correctly.

After the re-assembly my accessory lights & blinkers work but my temp gauge and fuel guage no longer work.

I took apart the fuel gauge and saw no burnt wires. I measured 13 ohms across the two leads.

I measured the resistance across my sending unit to body ground and got around 8 ohms.

I tried doing a bench test to see if I could ground out my fuel gauge... see the pictures below. I the needle did not move... I looked for 5v when it was connected to the battery I saw no voltage.

(note for testing purposes I did not connect the mercury switch to the 12 volt.... I also hear a clicking when I have this hooked up I read this is normal and is the opening and closing regulating the 5v, but again no 5v from that lead when connected.)

Anyone looking for the service manual for 1966 Plymouth you can get it for free at: http://www.mymopar.com/index.php?pid=109

Am I testing this wrong? What am I missing?

on board with this conversation....having same issue in my 66.

I metered out my board for continutity and found that when I checked from the ground to the 12v I was not seeing any... which is good.
Then I check from the 5v side and saw continutity which means it was grounded out.

When I pulled the dash out I cleaned up all the dirt and grime in it and I removed the board so it could get degreased and cleaned up. When I put it all back together the recessed slot (where the voltage regulator goes...the brass clips) is too small. If you are not careful when you put the board down it is possible to touch the case with the 5v side which shorts it out.

That being said I still do not see 5v off of my replacement voltage regulator from rockauto... I am guessing I fried it... I do hear clicking but not a lot in a consistent manner. So instead of ordering a new one I spent 8.00 at my local radio shack turned it into a solid stated voltage regulator. I did a bench test on this one and when I apply 12v I see 5v (4.97) on the other side.

If you want to build a solid state check out the url below... it list the parts need to make it. I will update the thread with pic's once the assembly is done
http://www.allpar.com/history/mopar/electrical2.html


I parted my oem regulator out, and placed the solid state regulator on the inside top. I hope to test it tonight, and will update the post tomorrow (If I get to test it tonight, because my sis-in-law is having a baby today)

That was my issue as described in my prior post.... my gauges work!!!
As promised here is the pic of the new solid state regulator.

Used some hightemp silicone since my cap is sitting in the case... I didn't want to ground anything out. I also put some medium strength locktite on the screw to the heat sink. I drilled two hole in the case to send wires out, and used hot glue to stop the wires from rubbing or shorting on the case... the third wire goes out the PCB board.

I also drilled holes in the metal posts to wrap the wire around... all I have left to do is throw a little solder on, and I am all done, and ready to put the dash back in again.

Anyone needing a new circuit board aka PCB for their dash check out http://www.premiumdashdecals.com/

So I did my bench test everything checked out. I metered out my wiring (violet) wire that connect to the dash... Placed the meter on ohm, and grouned black, and placed the red lead in the violet wire, and read ~67ohm, (with car running) so my guage read 1/4.... and at the fuel sender I get 8 ohm (that is correct, I just filled the tank). When the dash is hooked directly to the battery, and then I ground out the gauge I get a full tank... so the issue has to be wiring between the tank and the dash.


Once I track this down I will update the post again.

I did the exact same thing on my 71 Ranchero, however I think it needs a bit more than 5 volts. My gauges seem to read a little low. Otherwise they work perfectly. I may have to go to the LM317 adjustable series regulator to dial it in perfectly.

I had some dash gauge issues on my 66 Bel and I discovered the problem to be a bad ground. I believe one of the screw holes on the top side of the cluster has a piece of copper or brass foil so it can ground properly.

In my experience grounding the fuel gauge wire will peg the gauge hard (i.e. 0 ohms) so an actual full tank signal from the sender with a little resistance will only go to full or slightly beyond. If I understand you correctly, you get 8 ohms at the sender so I'd say things are normal.

I get 8 ohms when I use my meter at the tank and the tank is full, so I know that reading is correct.

I can adjust the upper and lower limits of the gauge with a screw driver, but I prefer not to mess with that until the I get the proper resistance from the wire at the dash. When I pulled the wiring off the dash, and put my meter on the violet wire which is the fuel sender,and grounded the other lead I got 67 ohms ~ and when the wiring is hooked up my tank reads only 1/4 tank. My bench test of the dash proved to me the gauge is capable of moving to the full position... so either the connection from the tank to the wire is bad, or the wire itself is bad.

At least that is my take on it.