68 Barracuda........ Temp and Gas Gauge Issue.

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OK, received the RTE voltage regulator and installed it.



I ran a secondary ground to the dash assembly to make sure that was not the issue.
None of the gauges (gas/temp/oil) are reading. I have pulsing power on the circuit board lugs feeding power to the gas, oil and temp gauges. I do not have pulsing power at the dash wiring connection (round connector) feeding the fuel sending unit and oil pressure sending unit. I do have pulsing power at the dash wiring connection for the temp gauge and pulsing power at the sending unit connection.
Are all the gauges done?
The weird thing is when I first started this odyssey, I did get the oil pressure gauge to work even though the gas and temp gauges didn't.
Any advice/comments would be appreciated.

Allan
 
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Ok, I now have a working oil gauge. The speed nut had a crappy connection. I had pulsing power on the gauge post but nothing on the speed nut or printed circuit. Removed the nut, sanded the face of the nut and cleaned up the board contact area and now the gauge works.
As mentioned above I have pulsing power to the temperature sending unit so I'm assuming the temp gauge is bad. I have no pulsing power on the gas gauge post feeding out to the fuel sending unit (although I do have pulsing power going in) so I'm assuming the gas gauge is toast as well?

Thanks,

Allan
 
you should be able to briefly ground each sender wire and get full needle swing if the gauge is alive.
Could be a failed temp sender. they just up and die without warning. Fuel sender could be dead or simply lacking its chassis ground path ( a metal jumper over the rubber fuel line ).
 
Do the above, but do it just for a few seconds to avoid burning out the gauges.

Better yet, order a 10 ohm, 1 watt resistor from www.mouser.com and put that between the temp sensor wire and ground, and then between the fuel sender wire and ground, and see if the respective gauges move to approximately full scale.

You are making progress!
 
And if you want to test the temp sensor, warm up the engine 'til hot, and then use you ohmeter to read the resistance from terminal to case. Hot, it should be roughly in the 15-25 ohm range.

And you can check the fuel sender by using your ohmeter to test from sender connection to sender/pick-up flange. 10 ohms full, 22 ohms 1/2 and 73 ohms empty are approximate resistance values to expect.
 
I've received a new (to me) gas gauge and temp gauge that I'll be installing. I want to stick with the RTE voltage regulator I bought so I'm wondering, do I need to take the fuel gauge apart to bend the arm as mentioned, or would putting an insulator on the back side of the gauge so it doesn't ground the internal voltage regulator suffice?

Thanks in advance.

Allan
 
RedFish said:
Disabling the original limiter is as simple as removing that previously mentioned little thin piece of metal from the back of the gauge.
So why would anyone suggest opening this gauge ? To see if it's cooked,,, and it very likely is.
Click to expand...

I installed the temp and gas gauges that I had picked up and tried to go back to the internal VR. I reinstalled the cluster into the car, and fired it up. I had pulsing power at the temp gauge sender connector and the oil and temp worked.



Ran the car for about 5 minutes and the temp and oil gauge started doing weird step adjustments and there was a little smoke coming from the temp/gas gauge area. Shut the car down, turned the key back on and now had continuous power on the posts I should have had pulsing power on. I'm assuming the internal VR in the fuel gauge decided to go on vacation. I pulled the gas gauge and isolated the ground contact on the back of the gauge, reinstalled the gauge and now will re-install the RTE VR. Before I reinstall, I just want to confirm that isolating the ground on the back of the fuel gauge is all I need to do regarding the OEM VR? I used some heavy pipeline tape to cover the contact.



There is no power going into the fuel gauge as that is now rerouted to the RTE VR. I'd really like to get this done today.
The fuel gauge never did read anything even when the temp and oil gauge was working.
This is becoming very frustrating.

Allan
 
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I would not play with tape and "the ground". The fuel gauges three (stud) terminals do the following:

Where 2 terminal gauges have the IVR (5v) input, and the sender connection, the three terminal fuel has......

sender

5V "out" to the rest of the gauges

12V "ignition" into the internal IVR of the fuel gauge.

So instead of depending on tape, you want to isolate (cut) the connection to the 12V ignition terminal inside the gauge, and you can use that stud which will (should) still have ignition power coming "down the trace" of the pc board........you can use that stud to feed 12V off to the external IVR

you need to feed your external EVR into the "5V" stud terminal. Since this terminal originally fed 5V to the other two gauges, it will still do that.

and the sender is as it was originally.
 
The 12V feed to the fuel gauge had already been cut by the previous owner to feed his VR. The 12V feed that normally would go to the pin feeding the gas gauge 12V now feeds directly to the RTE VR. There is no voltage fed to the fuel gauge other than the 5V coming from the RTE VR to the shared circuit. I put the tape on just as insurance because I wasn't sure about backfeeding into the VR from the 5V side. I really don't want to pull apart the fuel gauge if I don't have to.

Thanks for the comments.

Allan
 
Yes any outboard IVR could back feed through the original limiter with the right faults inside. Seee.....
The resistor wire does have insulation on it. In the case of the limiters, that insulation is surely toasted. The some idiot says go in there and bend it along with the bi metal beam it is wound upon. Yes that separates the mechanical contacts but... It could very well short some portion of the winding to the beam. Now... This winding has a ohms per inch resistance value. I'll cut to simplicity right here... Bent mechanical limiters not isolated from ground will very likely mimic a 3rd or ever 4th thermal instrument in the circuit.
Do you need to bend chit or not ? I really don't care what advise you believe and follow.
Do you need to isolate the 3 post instrument from ground whether you bend chit or not ? Absolutely !
 
So I reinstalled the cluster today with the RTE installed and the fuel gauge isolated as previously mentioned. The temp and oil gauge seem accurate.



I have pulsing power at the tank end of the fuel sender connection but not sure that what the gauge is showing is correct. I have about 4" of fuel in the tank and the gauge is still showing empty. It does seem to move once it has power. Maybe the sending unit is bad? I'll get back into it on the week-end.

Allan
 
Looks like they are working. Temp is a slightly high and oil is a bit low in my eye. Not to worry since these are within the range of a range indicator.
Gasoline... 80 ohms is no needle movement. Needle at off/home would be on top of the 'E'.
73 ohms is the first hash mark or more correctly the target dot above that hash mark. Approx' 3 gallons of fuel, while sitting level, should get the needle close to the target. Instrument age and other factors determine how well it works and how long it will work. Good luck with it.
 
now you'll need to look for why the oil pressure is to the low side of normal and water temp is well beyond acceptable. Of course lower engine / water temp will allow for higher oil pressure. So... break out the thermometer and find out just how hot it is, get it to run cooler first. Good luck
 
I have a 1967 Barracuda with a 273 and that is exactly where my temp gauge runs all the time.
 
I really wasn't too concerned with the temp reading. It was a hot day and had been sitting running for a while. Out of curiosity I'll use a temp gun on it on the weekend and see the temps at the thermostat and rad are.
 
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