Can You Bench an Oil Pressure Switch
February 8th, 2017, 02:58 PM
#1
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Can You Bench Test an Oil Pressure Switch
I took a short ride today after fixing the leaking hose between the water pump and the thermostat housing, and all of a sudden my oil light came on. I immediately pulled over and checked the oil(full). I was only a just over a mile from home so I took it real easy and limped the car home.
After shutting the car off, and turning it back on, no light. I revved it a couple times, no light. I revved it a minute or two later, light. Shut it off, started it, no light. Rev. no light. Can't get the light to come back on.
Now, I think it's electrical, because when I was fooling with the coolant hose, and started the car, I noticed the temp light wouldn't come on with the key on, or while cranking. It usually lights up at some point, and it didn't. Then all of a sudden, when I went to take a drive it worked again. I think the connection might have been loose on the switch/connector. But I really can't "prove" it to myself. And giggling it and turning the key doesn't seem to yield a no light condition now.
So, this leads me to think maybe the cluster is faulty. I can take it out and look, but If I can test the oil pressure switch. Besides screwing a oil pressure gauge into that hole where the sender for the idiot light is, I don't know how to check. I also don't have an oil pressure gauge, or a fitting for that size hole.
After shutting the car off, and turning it back on, no light. I revved it a couple times, no light. I revved it a minute or two later, light. Shut it off, started it, no light. Rev. no light. Can't get the light to come back on.
Now, I think it's electrical, because when I was fooling with the coolant hose, and started the car, I noticed the temp light wouldn't come on with the key on, or while cranking. It usually lights up at some point, and it didn't. Then all of a sudden, when I went to take a drive it worked again. I think the connection might have been loose on the switch/connector. But I really can't "prove" it to myself. And giggling it and turning the key doesn't seem to yield a no light condition now.
So, this leads me to think maybe the cluster is faulty. I can take it out and look, but If I can test the oil pressure switch. Besides screwing a oil pressure gauge into that hole where the sender for the idiot light is, I don't know how to check. I also don't have an oil pressure gauge, or a fitting for that size hole.
Last edited by jpc647; February 9th, 2017 at 06:11 PM.
February 8th, 2017, 03:10 PM
#2
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Location: West Michigan
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You probably damaged the send unit or connector or wire while replacing the hose. But better not to assume. Whenever you have an indicated low oil pressure, the first step is to pull the sender and screw in a mechanical gauge to get a second opinion. They aren't that expensive, and you'll probably need it again someday. If the pressure checks OK, then you can move on to diagnosing where the problem is (which is much more likely to be under the hood than in the dash).
February 8th, 2017, 04:49 PM
#4
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Bad sender or wire.
That said, you need a mechanical pressure gauge anyway, so now's the time.
If you want to test the switch, just hook it up to compressed air (bicycle pump is fine) and see if it clicks off above about 4-5psi.
Rule of thumb: If you've got hydraulic lifters and you lose oil pressure, they'll clatter immediately. If the lifters were quiet, your pressure was fine.
- Eric
That said, you need a mechanical pressure gauge anyway, so now's the time.
If you want to test the switch, just hook it up to compressed air (bicycle pump is fine) and see if it clicks off above about 4-5psi.
Rule of thumb: If you've got hydraulic lifters and you lose oil pressure, they'll clatter immediately. If the lifters were quiet, your pressure was fine.
- Eric
February 8th, 2017, 05:04 PM
#6
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February 8th, 2017, 05:35 PM
#7
dualquadpete
Join Date: Dec 2016
Location: Blackstock Ont. Cda
Posts: 43
Had a similar problem but with HOT light while driving, wire fell off sender and was grounding out on rough road[light flashing on & off] crimped the connector and pushed it back on, problem solved!!! You might have knocked the wire off????
February 9th, 2017, 09:15 AM
#8
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Bad sender or wire.
That said, you need a mechanical pressure gauge anyway, so now's the time.
If you want to test the switch, just hook it up to compressed air (bicycle pump is fine) and see if it clicks off above about 4-5psi.
Rule of thumb: If you've got hydraulic lifters and you lose oil pressure, they'll clatter immediately. If the lifters were quiet, your pressure was fine.
- Eric
That said, you need a mechanical pressure gauge anyway, so now's the time.
If you want to test the switch, just hook it up to compressed air (bicycle pump is fine) and see if it clicks off above about 4-5psi.
Rule of thumb: If you've got hydraulic lifters and you lose oil pressure, they'll clatter immediately. If the lifters were quiet, your pressure was fine.
- Eric
You're probably right. I just haven't found a good place to mount the array of gauges. I have a cheap Sunpro Water temp gauge mounted under the dash and slighly angled toward the driver seat, but there isn't room/I would need a new cluster to accommodate both gauges. I'll do that with the pump though, just for curiosity.
The lifters certainly weren't clacking. The car sounded normal.
that's not a bad idea. EBay it is!
February 9th, 2017, 03:47 PM
#11
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Location: West Michigan
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Maybe your thumb is longer than mine. I once stripped the oil pump driveshaft in an '86 G-body while driving. I pulled over, checked the oil, wiggled the send-unit wire, then decided to take my chances, ASSuming that the send unit was bad. The lifters didn't start clicking (not clattering) until after driving 3 miles down the road and idling for 5 minutes at a fast-food joint. Surprised me it wasn't sooner. Upon dropping the pan to replace the shaft, the bearings looked fine.
February 9th, 2017, 04:07 PM
#12
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Wow. I've had momentary loss or pressure a large number of times in American (Olds and other) V8s over the years, and have always immediately heard lifter clatter.
Interesting.
- Eric
Interesting.
- Eric
February 9th, 2017, 06:13 PM
#13
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Maybe your thumb is longer than mine. I once stripped the oil pump driveshaft in an '86 G-body while driving. I pulled over, checked the oil, wiggled the send-unit wire, then decided to take my chances, ASSuming that the send unit was bad. The lifters didn't start clicking (not clattering) until after driving 3 miles down the road and idling for 5 minutes at a fast-food joint. Surprised me it wasn't sooner. Upon dropping the pan to replace the shaft, the bearings looked fine.
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