lost water temp and oil pressure gauges simultaneously
08-05-19, 04:59 PM
#1
lost water temp and oil pressure gauges simultaneously
So, I changed my oil on Friday and then took it for a drive. At some point (probably while changing the mixture screw for cooler ambient temps) my water temp and oil pressure gauges went to zero. I wiggled wires and checked continuity from the senders to the connector across the engine bay, the wiring in the engine bay seems to be OK. I have a mechanical oil pressure gauge, so I know the engine itself was OK. But the ones behind the steering wheel are dead. Seems like when I turn the car on, they will slowly rise to just above zero and not move.
Seems weird that both would stop at the same time, right? Or is there a single component that could fail and kill both?
When I first had it running there was intermittent, rapid relay click under the dash that would affect operation of the oil pressure gauge. One random relay was hanging by its wires near my clutch foot. At some point I jammed it up under the dash and after that the oil pressure gauge worked. But I can't find anything on the wiring diagram that lines up with that location and has anything to do with either non-functional gauge.
Does this thing ring any bells with anybody?
Seems weird that both would stop at the same time, right? Or is there a single component that could fail and kill both?
When I first had it running there was intermittent, rapid relay click under the dash that would affect operation of the oil pressure gauge. One random relay was hanging by its wires near my clutch foot. At some point I jammed it up under the dash and after that the oil pressure gauge worked. But I can't find anything on the wiring diagram that lines up with that location and has anything to do with either non-functional gauge.
Does this thing ring any bells with anybody?
08-05-19, 05:40 PM
#2
84SE-EGI helpy-helperton
Simple things, first; check the interior fuse block for METER fuse (10A or 15A) which could result in the signal not making it to the meter back.
From there, the circuits for the sending units are pretty straight-forward, and it sounds like you've checked those pretty closely. Occasionally, I've had my Oil Pressure gauge stick on the dash, and if I flick my fingernail against the plastic cover panel, it jumps to life. Had that happen on my first startup of the replacement engine that sat for a decade, and my heart stopped while it was running and I noticed no oil pressure - tapped my finger on the gauge cover and it jumped to where it needed to be,... whew...
Coolant Temp sensor is either on the back of the Water Pump or the bottom of the Radiator, I can't remember which is used for the gauge reading (*probably the Water Pump). Since you had an issue in the past with a relay (Check & Cut Relay) under the DS footwell in the past, it might be worth your while to move stuff around up in there again and see if you can find the relay that carries those signals - it's probably the relay that powers up the sending units.
Long shot; could also be related to the Oscillator Relay (located in front of the battery - horrible placement) which was designed to buzz if / when the oil pressure dropped to alert the driver to a problem. This last one is a VERY remote possibility, as the Oscillator Relays on our cars usually rotted out from battery acid getting on them, and all it did was prevent any buzzer from going off if the oil pressure dropped. I'll bet 99.9% of our cars DO NOT have a working Oscillator circuit...
From there, the circuits for the sending units are pretty straight-forward, and it sounds like you've checked those pretty closely. Occasionally, I've had my Oil Pressure gauge stick on the dash, and if I flick my fingernail against the plastic cover panel, it jumps to life. Had that happen on my first startup of the replacement engine that sat for a decade, and my heart stopped while it was running and I noticed no oil pressure - tapped my finger on the gauge cover and it jumped to where it needed to be,... whew...
Coolant Temp sensor is either on the back of the Water Pump or the bottom of the Radiator, I can't remember which is used for the gauge reading (*probably the Water Pump). Since you had an issue in the past with a relay (Check & Cut Relay) under the DS footwell in the past, it might be worth your while to move stuff around up in there again and see if you can find the relay that carries those signals - it's probably the relay that powers up the sending units.
Long shot; could also be related to the Oscillator Relay (located in front of the battery - horrible placement) which was designed to buzz if / when the oil pressure dropped to alert the driver to a problem. This last one is a VERY remote possibility, as the Oscillator Relays on our cars usually rotted out from battery acid getting on them, and all it did was prevent any buzzer from going off if the oil pressure dropped. I'll bet 99.9% of our cars DO NOT have a working Oscillator circuit...
08-05-19, 06:55 PM
#3
Coolant temp sensor is near the oil pressure sender, it has a weird bullet connector I haven't found a replacement for so I'm using an alligator clip.
C&C relay works, I know because the warning lights turn off when I turn the engine on.
Good call on fuses. I'll try to check the purpose of that mystery relay by my left foot too
C&C relay works, I know because the warning lights turn off when I turn the engine on.
Good call on fuses. I'll try to check the purpose of that mystery relay by my left foot too
08-07-19, 11:32 AM
#4
Meter fuse is fine.
Studying the wiring diagram, there doesn't seem to be a thing that would fail causing only both of those gauges to stop working.
Still chasing the mystery relay wiring under the dash.
The car isn't exactly unmolested...
Studying the wiring diagram, there doesn't seem to be a thing that would fail causing only both of those gauges to stop working.
Still chasing the mystery relay wiring under the dash.
The car isn't exactly unmolested...
08-07-19, 01:13 PM
#5
ancient wizard...
Pull cluster and check each sender wire for continuity and resistance,resistance should be very low.
Next inspect the pins on back of cluster and in connector to be certain they’re tight and oxidation free.
Flip cluster over on a towel and inspect printed circuit
You have identified which two pins in connector are for oil/temp gauges. Check for continuity from pin on circuit board to each respective gauge pin. Should be 0 resistance. Check each gauge for resistance,results should be similar.
Does the voltmeter operate correctly? I think the feed for oil/temp/fuel gauges is the same.
Somewhere in the above you will find something.
I have had success in repairing printed circuit board with low temp solder and 15 watt soldering iron,sometimes necessary to solder small jumper wire on each side of a break to make a permanent repair.
Next inspect the pins on back of cluster and in connector to be certain they’re tight and oxidation free.
Flip cluster over on a towel and inspect printed circuit
You have identified which two pins in connector are for oil/temp gauges. Check for continuity from pin on circuit board to each respective gauge pin. Should be 0 resistance. Check each gauge for resistance,results should be similar.
Does the voltmeter operate correctly? I think the feed for oil/temp/fuel gauges is the same.
Somewhere in the above you will find something.
I have had success in repairing printed circuit board with low temp solder and 15 watt soldering iron,sometimes necessary to solder small jumper wire on each side of a break to make a permanent repair.
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