I despise chasing down electrical problems. Some of the oddest things occur at times. I had a engine run on problem where the engine would intermittently continue to purr like a kitten when I turned the key-off. This intermittent problem, which was somewhat self-inflected as I have a MSD box and I needed to install a diode in the gen light wire (per MSD instructions, it is right there if you look.). Here is the link to that thread. https://classicoldsmobile.com/forums...s-help-136600/ This problem appears to be solved as I have had no more issues over the past week.



However, I am still having issues with the rally gauges that are driving me nuts. (Please keep in mind, that I bought my 70 442 as a roller, and it has been completely tore apart and put back together.) So, I have no base lines to go back too.



So here we go. 2 problems: 1) The gas gauge only reads half of what’s there. So, the gauge reads ½ full when the tank is full and once I hit a half of a tank the gauge reads empty. 2) About an hour into a two-hour road trip the temp gauge quit working, and has not worked since.



I am working on the gas gauge presently. I am starting to believe that the gauge is faulty, but I am still working through some tests. I have been running various continuity test and here is where I believe that I am at:

1. Running a jumper wire from the neg battery terminal to the multimeter to test the tank ground at the body shows no resistance. Ground should be good.
2. Fuel sending unit is an original sending unit from another car. Body shop tested it before they put it in and said it checked out. I believe this to be true as the couple of times I have checked it: a couple of weeks ago, it had ¾ of a tank and read 64 ohms by testing the lead wire in the trunk (Gauge read slightly less that ¼ tank), and NOW it has about a half tank and reads 47 ohms. (Gauge reads empty). My understanding is that the sending unit provides approximately 88 ohms resistance at full, down to no resistance at empty. I have shook the car, and have noted oscillation in the ohm reading as the gas sloshes in the tank.

Assuming the sending unit is doing its job correctly based on this information.

• I have tested continuity of the rear body harness using a jumper wire and multimeter to connect the two ends and have no resistance.
• I have tested the lead wire in the trunk, grounded to the trunk latch I have 47 ohms, (again it has about a half of a tank of gas-gauge reads empty)
• I have testing using a jumper wire from the neg terminal of the battery to the rear harness plug in the interior of the car, and have 47 ohms.
• Therefore, I believe I have ruled out the rear-body harness.

Now here is one of the first quirks that is driving me nuts, and it is the connection between the rear body harness and the dash harness. The resistance jumps up from 47 ohms to 70 ohms.

1. Disconnect ready body wiring plug and dash wire plug. Do a continuity test from the dash harness plug to the gauge plug and get no resistance.
2. Plug it back together, still 70 ohms at the gauge plug. Insert multimeter probe into the back of the dash harness plug 70 ohms, but 47 ohms is still the reading at the rear body wiring plug when apart.
3. Ok, terminal must be dirty. Finally found the right size finishing nail to allow me to pull the wire from the dash plug. Do my best to clean it. I take the single wire removed from the dash plug and plug it directly onto the rear body harness gas gauge terminal. We are back to 47 ohms, check gauge plug: 47 ohms. Great, we move on- WRONG.
4. Place single terminal back into dash harness plug: 70ohms. ARRRR. Take it back out, clean some more, reconnect as a single wire to the rear body harness- 47 ohms. Wiggle wire, flip single wire over and re-plug to rear body harness, wiggle wire, bend straighten wire just past terminal: constantly get 47 ohms at the gauge plug. GREAT, we move on- WRONG!
5. Place it back in the dash harness plug connect the two harnesses together, and you guessed it – 70 ohms.

To make matters worse, these results should mean that the actual gas gauge would read higher than the fuel level in the tank, which is the opposite of the problem I am having. However, It is difficult to further trouble shoot the rest of the circuit until I get a consistent reading from the rear of the car to the gauge plug. The gas gauge wire in the dash plug has a blank terminal on the one side, and a green wire on the other side. As a test, I plan on puling the adjacent (temp) green wire from the dash plug and see what happens with the ohm readings. Any other suggestions?

Thanks