Quick oil pressure gauge wiring question Options

[Tdskip]

Good morning - hope everyone is going well.

I have an oil pressure gauge that looks like this one (not my car in picture but same sender),

1) I believe one terminal is for the actual pressure reading and one if for the warning light?

2) If that ^^^^ is correct does it matter which terminal is which? in other words is one terminal specific for the actual pressure reading?

Thanks!

[rgalla9146]

Yes, it matters.
One pole acts as a ground until oil pressure takes it away.
The other provides the variable signal to the gauge.
What are the labels on the poles ?
In mine the G pole is for the gauge. Green wire.
WK (green/red trace) for the lamp

[Tdskip]

Yes, it matters.
One pole acts as a ground until oil pressure takes it away.
The other provides the variable signal to the gauge.
What are the labels on the poles ?
In mine the G pole is for the gauge. Green wire.
WK (green/red trace) for the lamp

@rgalla9146 - thanks, let me look more closely. Thanks for the response, very helpful.

[IronHillRestorations]

There's no wire in the 914 harness for an oil pressure gauge, so if a PO hasn't put one in, you'll have to run one. If your car doesn't have/need heat, you can use the heater blower switch wire without too much trouble.

[Tdskip]

There's no wire in the 914 harness for an oil pressure gauge, so if a PO hasn't put one in, you'll have to run one. If your car doesn't have/need heat, you can use the heater blower switch wire without too much trouble.

Thanks Perry - the rebuild 2.0L that I put in the former turbo car has the same type gauge but was only running one lead from it, I have a cockpit oil pressure gauge but didn't want to assume the PO had it right. I also have a spare oil pressure gauge in the large assortment of parts that came with the "race" car and wanted to make sure I did this the right way.

Thanks for the tip on using that circuit.

Hope you are doing well.

[Maltese Falcon]

You can always give a call over to North Hollywood Speedometer (on Lankershim) and ask about the VDO terminals (unless marked). Small shop and are always cool with my questions !

[Tdskip]

You can always give a call over to North Hollywood Speedometer (on Lankershim) and ask about the VDO terminals (unless marked). Small shop and are always cool with my questions !

Good reminder, good people and great shop.

Thanks!

[ClayPerrine]

There's no wire in the 914 harness for an oil pressure gauge, so if a PO hasn't put one in, you'll have to run one. If your car doesn't have/need heat, you can use the heater blower switch wire without too much trouble.

The relay board has an unused trace in it, and the pins on the harnesses are not filled. You can add a green/red wire to the engine harness, and to the chassis harness.

I did this on Betty's car. I scavenged the wires out of a old junk 911 harness. It looks like it came that way.

Clay

[framos914]

On same topic.
I have the dual sender.
My console gauge reads 0-70 PSI seems to work fine.
My dash light does not operate like it should. Wiring is good, it lights when I ground the wire connected to the sending unit. When I check resistance at sender with engine off its 15-16 ohms, engine on it's open.
Question, is that too much resistance to turn on the light? If bad which type of sender should I replace it with? I've seen some 0-150 PSI but my gauge only goes to 70 PSI.

Thanks

[Tdskip]

You are asking, just to be clear, about the oil pressure warning light, correct?

Since the gauges are sensitive to a specific sender I'd expect the warning lights are as well, but please get other opinions/expertise.

[framos914]

Yes, the oil pressure warning light.
On the sender the G pole connection goes to the gauge and that works fine registering the pressure in PSI.
When i disconnect the wire at the WK pole of sender and ground it to engine the light turns on proving wiring to the warning light is good.
I believe the sender is bad, but the ones I see are 150 psi, don't think it will work with my 0-70 PSI gauge.
It's a 1974 2.0 engine.

[GregAmy]

Those senders have two circuits: one variable for the gauge and one switched for the light.

Since you've verified the light circuit functions properly when the wire is grounded, I agree with your assertion that the sender's switched circuit is bad.

[rgalla9146]

Yes, the oil pressure warning light.
On the sender the G pole connection goes to the gauge and that works fine registering the pressure in PSI.
When i disconnect the wire at the WK pole of sender and ground it to engine the light turns on proving wiring to the warning light is good.
I believe the sender is bad, but the ones I see are 150 psi, don't think it will work with my 0-70 PSI gauge.
It's a 1974 2.0 engine.

Any chance you used teflon tape on the sender ?
Doesn't seem posible the gauge works but the light doesn't ground.
Test the sender directly with a test light.
Attach one leg of light to battery, other to post on sender.
Lamp should be on untill engine starts. Oil pressure removes the ground.

[framos914]

Any chance you used teflon tape on the sender ?
Doesn't seem posible the gauge works but the light doesn't ground.
Test the sender directly with a test light.
Attach one leg of light to battery, other to post on sender.
Lamp should be on untill engine starts. Oil pressure removes the ground.
[/quote]

Was thinking about Teflon tape as a possibility since the engine was rebuilt recently at a shop.
Checked w/ test light, light on for variable side no light fot switched side. I just read that resistance from WK pole to ground should be less than 10 ohm but I get 15-16.
Tight fit location next to distributor, hope I can get it out without moving distributor to check for teflon tape. If no tape, will have to replace it.

[GregAmy]

You can run a simple ground wire from the engine block to teh body of the sender to check that.

Is it screwed directly into the engine? Generally speaking, that's a bad idea. It would not be unusual for the engine vibrations to cause the small thread to fatigue and the sender to fall off...that's a bad thing.

"Best form" is to use a stainless-braided line from the port on the block to the sender mounted somewhere else, strapped by its body. That takes the stress off the threads.

[gereed75]

I believe there are two different senders with two different 911 part numbers. The sender output must match the gauge or the reading will be off. I think Pelican has a tech how to on this.

[framos914]

Thanks Guys,

it is a bad switched circuit on the sender.
Was making a rookie electronics mistake and not disconnecting the wire at sender before checking resistance. Body does have good connection to ground but the WK pole does not.

Now to buy the correct one and replace.

GregAmy:
It is screwed directly into the case.

[GregAmy]

GregAmy:
It is screwed directly into the case.

Now's a good time to address that...<tick...tick...tick...> - GA