is there a way to repair them? i have not found anything. just coolant pegging issues and fixs. and replacing them with some aftermaket gauges in the rally gauges housing. im thinking about that, but i want as close to stock/restored modified look as i can get.
when i turn power on to the car (not cranking) my volts jumps up to about 13+ volts and my oil pressure goes immediatly to 40 psi. when the car is started and runs, the volts jump to 18 and the oil pressure jumps to 80. i know those readings are not correct in any way. how do i fix this?
im using a new OPS from a 98 4300. i switched over to the 88's connector and OPS type. the 88 fiero 2.8 and the 98 blazer 4300 use the same OPS. and that is a 90 ohm max type from what i understand. so its the gauge from what i am understanding. i need to check the resistance of it to see what it says. but my volts gauge us also reading inaccuratly.
Your 13+ volts at the in-car voltmeter seems high with the engine off, but a fully charged battery will produce more than 12V, and if you allow a 10% error in the gauge (hey it's 80's quality here), it's not unreasonably high. When you're running the engine and it reads 18V in the car, I would check what voltage you actually have using an independent voltmeter at the battery. It should be between 14V and 16V max. If it's more, your alternator's voltage regulator is giving up the ghost and producing a higher than normal voltage. This could affect your oil pressure gauge reading while the engine is running too, but it doesn't explain why it's so high with the engine off. For the oil pressure gauge, I'd suspect your sender is faulty. It should be zero ohms with the engine off, but it sounds like it's at mid scale ~45 ohms.
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08:00 PM
americasfuture2k Member
Posts: 7131 From: Edmond, Oklahoma Registered: Jan 2006
ive tested my batt with a DMM. it reads 11.50 volts. when running it reads 14v± at the DMM. im looking at what tuner pro is showing what the voltage is from my last data log. but if those arent the problems, how do i fix the gauges.
I'd say there are two different problems with your gauges:
To deal with the oil pressure gauge, it helps to understand how it works. There are three wires, the pink/blk provides 12V, the blk wire provides a direct ground, and the tan wire provides a variable resistance to ground through the sender. So to test all three circuits for proper function:
1. Since you've tested the voltage from the battery and alternator, and since the gages do show signs of getting power, you can eliminate the first wire and voltage as a source for your problem.
2. Next, you should do as I recommended in my earlier post about checking the variable resistance across the sender to ground. Unplug the tan wire at the sender and measure the resistance from the sender's blade terminal to ground. It should measure zero ohms with the engine off and somewhere around 45 ohms with the engine running. If not, replace the sender. If the results are good, then leave the sender disconnected and also disconnect the connector from the back of the gauges. Using your ohmmeter again, place one lead on one end of the tan wire (pin B) and the other to ground. If you get anything except infinite ohms, your tan wire is grounding out accidentally somewhere along the path between the sender and the gauge.
3. Lastly, you should use your ohmmeter again and put one lead on the black wire that goes to the gauges connector (pin H), and the other to ground. If you get anything but 0 ohms, your grounding point (G201) for both gages needs to be cleaned and re-grounded. G201 is behind the radio on the vertical metal upright that supports the center of the dash.
Now for your volt gauge. If you found any problems during your troubleshooting for the oil pressure gauge and corrected them, then check now to see if by having solved the oil pressure gauge problems, you have solved your volt gauge problems too. If it still shows 13 or more volts with the engine off, and 18 V with the engine running, then:
1. Buy a small variable resistor (say 0 to 50 ohms) and splice two legs into the car's voltmeter power lead that runs from the pnk/blk wire (pin A) to the voltmeter on the printed circuit, and the third leg to ground as the manufacturer of the resistor states. Since the voltmeter and oil pressure gauge share the same power lead, be sure to tap into the power lead AFTER it branches to the voltmeter. Once you've done this, then simply turn the key to run (engine off), and adjust the variable resistor until you get 12V showing on the car's voltmeter. Then start the car and fine tune the adjustment to show 14V when running; Or
2. Go out and scrounge a new voltmeter from a scrap yard and replace the gauge.
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09:35 AM
Jun 12th, 2009
americasfuture2k Member
Posts: 7131 From: Edmond, Oklahoma Registered: Jan 2006
i talked to some of the electronic techs i see at work about this, and they said that fix is more of a bandaid. and its seeming in order to fix a gauge like that is to get a new gauge.
