Temp and fuel gauges no bueno

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jcmeyer5

jcmeyer5

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Finishing up odds and ends on dads 69 Dart. One of those is to get the temp and fuel gauges working. I went through all of the engine wiring, so I know the wiring for the temp gauge is good and hooked up. Let’s start there.

I have the regulator in hand. I am testing it with a 12V power supply. And I am monitoring it with a multimeter. It doesn’t hold a constant 5V. In fact, it never makes it to 5V. It oscillates between 0 and 4V. I expected a steady 5V from a working unit.

I am getting a solid state unit, but I wanted to test this old unit as part of my trouble shooting. I have a video of what the meter reads. Given the IVR is supposed to switch 0V to 12V back and forth, I think it’s bad, but I still need to ask. All I need to know is if the IVR readings show a good unit or a bad one.

 
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If you are talking about the old original IVR unit, they pulse like a flasher and it may "confuse" your meter. You will never read anything "that makes sense" from one of those

Typical problems: (in no order.........)

1....Add a pigtail from the cluster common ground point and bolt that to the dash frame/ column support
2....Obviously the IVR could be toast
3....The contact fingers for the IVR often don't make good contact with the board traces. Clean and solder jumpers across from contact fingers to board traces
4....Gauge nuts often come loose/ corroded. To "scrub" the board clean loosen/ tighten the nuts a few times
5....The harness PC board pins are crimped and corrode or come loose. Clean, solder, repair, etc
6...."Jig" it up and test "end to end" with test resistors for the senders and 12V to the appropriate harness pin on the board

Gauge test resistances

c-3826-jpg-jpg-jpg.jpg
 
Mine was doing same thing on 67 cuda. I checked for 5V out of each gauge(except ammeter) and all was good?
 
You need an analog meter to get an accurate reading. If you see the voltage swing you should be good to go. Ground your sending unit wire and see if the gauge moves.
 
67Dart273 said:
If you are talking about the old original IVR unit, they pulse like a flasher and it may "confuse" your meter. You will never read anything "that makes sense" from one of those

Typical problems: (in no order.........)

1....Add a pigtail from the cluster common ground point and bolt that to the dash frame/ column support
2....Obviously the IVR could be toast
3....The contact fingers for the IVR often don't make good contact with the board traces. Clean and solder jumpers across from contact fingers to board traces
4....Gauge nuts often come loose/ corroded. To "scrub" the board clean loosen/ tighten the nuts a few times
5....The harness PC board pins are crimped and corrode or come loose. Clean, solder, repair, etc
6...."Jig" it up and test "end to end" with test resistors for the senders and 12V to the appropriate harness pin on the board

Gauge test resistances

View attachment 1715967300
Click to expand...

1. Did that already
2. Ordered an RTA unit
3. I didnt look at this. I will take a gander.
4. I had the whole assembly out, cleaned, dieletric grease, etc.
5. I checked the pins. They were all tight. I will check again.
6. Looks like this is next on my list
 
Okay update. I took out the cluster to bench test. The pins were tight and getting good connection, but I soldered them for added peace of mind, I checked continuity on all 3 pins at play, and all is checking fine. I tested the fuel gauge, and it reads about 3/4 with a 18ohm resistor. The temp gauge did not respond at all. I am going to test them out of the cluster to see if they are any different.

what are my options to correct the fuel gauge? I know it won’t be perfect, but showing full when it is full is the goal. I’ll update on temp later.

EDIT: Rereading @67Dart273 post above and full is 10 ohms, where half is 23 ohms. Maybe I am right where I should be with a 18 ohm resistor.
 
You can use a meter match to correct the gauge readings with the replacement sender that does not read correct.
I just calibrated one today and documented the readings. Basically I drained the tank and read the sending unit. 74.3Ω empty. The meter match has four calibration points so I used empty, 6 gal 10 gal and full. 6gal (3/8) is 41.1Ω. 10 gal (5/8) is 21.7Ω and full was 9.9Ω. These are readings directly off the replacement sender with the exact mount noted in the tank.

Are you working with an OEM sender or a replacement? You will never get a replacement one to read correctly through the whole range simply by adding a resistor due to the shape of the tank. The new senders do not account for the odd shaped tank.
Someone could make a small fortune if they made a correct sending unit for mopars that actually worked.
 
@MoparMike1974 stock style aftermarket. Depending on the brand, it could be reading correctly. I’ll stick it back on the car and see how it behaves. Like I said, I was using an 18 ohm resistor. It shouldn’t have read full.

pulled the temp gauge apart. I see the broken filament. Is there any way to repair it? What is it made of?
 
I don't know of any way to fix them other than finding someone to rebuild the gauge who is "in the business."
 
MoparMike1974 said:
You can use a meter match to correct the gauge readings with the replacement sender that does not read correct.
I just calibrated one today and documented the readings. Basically I drained the tank and read the sending unit. 74.3Ω empty. The meter match has four calibration points so I used empty, 6 gal 10 gal and full. 6gal (3/8) is 41.1Ω. 10 gal (5/8) is 21.7Ω and full was 9.9Ω. These are readings directly off the replacement sender with the exact mount noted in the tank.

Are you working with an OEM sender or a replacement? You will never get a replacement one to read correctly through the whole range simply by adding a resistor due to the shape of the tank. The new senders do not account for the odd shaped tank.
Someone could make a small fortune if they made a correct sending unit for mopars that actually worked.
Click to expand...
Man, I musta been Blessed, after all the crap I delt with for over 30 years with these rides. The current set up in my Duster is Damn near spot on!!
 
So I was able to score an entire gauge cluster off ebay. Two chances to get a single good gauge. Pulled the temp and fuel gauges. Looked at the temp gauge first... that thing is crispy, and the filament is broken. Pulled the fuel gauge apart and it looks nice and clean, and the filament is intact. I hooked it up to my test bench and it responded, but only moved about 1/8 of the gauge. I then saw the tangs that hold the needle were spread. I removed the needle, tightened them up, and installed the freshly painted needle from the old temp gauge. Hooked it up, and I have a full sweep on the gauge! So I will be reinstalling this evening and crossing my fingers that no other problems exist!
 
Another note... oddly enough, the temp gauge from the ebay cluster had a different configuration than the original gauges in our car... its as if the assembly was upside down and flipped. The gauge I ended up being able to use though matches the configuration of the original temp gauge, so nothing lost. Just was odd to see two different configurations.
 
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