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H'okay. So I installed an Autometer Electronic Oil Pressure gauge. The problem is, as soon as you turn the car on, it pegs at 100psi and stays there. I have all the wiring run correctly, unless there is a problem with my ground. I ran my ground under the dashboard like I have for all my other electronic addons. Do I need to run the ground out to the engine block for it to work correctly? The sender says it grounds through the block via the adapter (and my adapter is made out of a steel drain plug, eff those flimsy brass ones)


I read this, but didn't get a good solid answer out of it. http://www.yourcobalt.com/forums/chevy-cobalt-owners-lounge/10016-gauge-problem.html

So, just looking for suggestions.
 

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I had the same problem on mine when I first installed it -- read 100 PSI at idle. Try running a temporary ground directly to the block from the gauge -- I ended up doing that to get it to read correctly. At least you'll know if that's your problem too.
 

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I took a length of wire and hooked it to the back of the gauge and had my dad hold the other end on the block, and no change. i mean, I could try running a proper ground as well....
 

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hmmmmmm, my autometer is grounded under the dash
but it doesn't peg 100.

Did you use teflon tape on the sending unit or adapter ?
I have seen it stop the ground for the sending unit......
just a thought here.
 

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I took a length of wire and hooked it to the back of the gauge and had my dad hold the other end on the block, and no change. i mean, I could try running a proper ground as well....
The oil pressure valve holds pressure up to 75 psi - when cold it can go up to 80 psi. At idle you can have as low as 17 psi and factory specs call for 50 psi @1000RPM minimum.

If you are running a partial sweep gauge you should have the large oil sending unit...full sweep gauge uses the small oil sending unit...any chance there's a mix-up?

---------- Post added at 07:41 PM ---------- Previous post was at 07:38 PM ----------

hmmmmmm, my autometer is grounded under the dash
but it doesn't peg 100.

Did you use teflon tape on the sending unit or adapter ?
I have seen it stop the ground for the sending unit......
just a thought here.
...another possibility...try running a short piece of wire and ground the sending unit to the block and see if there is any change.
 

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Discussion Starter #8
My 12v source is off my accessory line, my gps, radar, etc etc.

I have teflon on the adapter and the block fitting. I can try taking that all off.

I bought the whole thing off a guy on here. Its an old school or hot rod gauge and the sender is like the size of a D battery I think.
 

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Try running a wire from the back of the gauge to the strut tower on the driver side where the ground is, also run one from the sending unit to that should fix your problem. Otherwise check your power source for proper voltage? You are getting voltage from somewhere there is just no signal that is why the gauge is pegged.
 

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def sounds like your ground is loose or something. i have a mechanical so i just ground mine to the strut tower with all my gauges. but with the electric senders need to be grounded to themselves on the threaded part. so yeah, the engine block. my coolant sensor works the same way. if your connections are looking good it could also be a bad sender.
 

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Discussion Starter #15
Robplen: My dad made me one out of a factory drainplug.

I called Autometer, ran thru a bunch of tests of the gauge and the sending unit. First off, Autometer says Teflon tape on the threads is fine and a good idea. Not a problem, Continuity checks out. After talking to their rep, and running their tests, they think my sender is bad, so they are sending me a new sending unit for free. Hopefully I will get it in Friday night / saturday depending on when it comes.
 

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Changing the sending unit did not make a difference. I left the sender line off, turned the car on. as soon as the sender line touches anything metal it pegs, with the ground connected or disconnected. So I am thinking bad gauge?
 

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Changing the sending unit did not make a difference. I left the sender line off, turned the car on. as soon as the sender line touches anything metal it pegs, with the ground connected or disconnected. So I am thinking bad gauge?
Since the sending unit is a rheostat, touching the sending unit wire directly to ground should peg the gauge. do you have an ohmmeter? check the ohms through (out of) the sending unit -- you should get different readings when the engine is off Vs running. Do you have the gauge wires connected correctly...seriously take another look!
 
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