Hey Guys,

Does anybody know how to test the output of the oil pressure sender with a multimeter?

I know it's somehow based on resistance, but it's only got one wire, so I'm a little confused.

I'm trying to track down why my oil pressure gauge stopped working, and I know that it's either the sender, the wire, or the gauge. I figure since I've got a multimeter I could test the sender and get it out of the way first.

GSL-SE Addict? Kentetsu? Anybody?

Jon

 

The OP sender is just a variable ground, based on pressure. The higher the pressure, the lower the resistance will be.
I can't quote the resistance values, but I'm sure they would be listed in the FSM.

 

Yea, you should be able to just measure resistance between the one wire and ground. If I remember right, the factory service manual shows what resistances to use to test the gauge, so you can just use those as the values that the sending unit should read at a given pressure.

Rich

 

Iirc, if you ground the sender wire, the gauge pegs. If it doesn't, the gauge itself may be at fault.

 

That should be correct.

Rich

 

If the gauge doesn't peg, pull the cluster and check the fine white wires that wrap around the bar on the back of the gauge, you'll know what I mean when you see them. If there is any discoloration, browning or blackening of the wires, the gauge is toast.

 

Just in case anyone wants to know, the fine white wires wrapped around the bar on the back generate heat as current flows through them. The "bar" is actually a bi-metal strip. Metals expand at different rates, so when you put two of them together and heat them, the strip bends toward the one that expands the least. This strip is connected to the needle on the gauge, so as it bends, the needle moves.

Yes, I'm a geek.

Rich

 

i had always wanted to know how they worked. now i do

 

Simple bi-metallic strip. 2 different metals, that expand at differential rates, are sandwiched together. When heat is applied, it bends, moving the needle.

 

ok im having a similar issue but its with the temp gauge.
i have a positive wire on one terminal and the sender hooked up to the other.
is there some relay i am missing because after running for a minute on a cold engine the gauge goes goes all the way to hot. i have tried multiple senders and gauges with the same results.

 

Temp gauges can fail the same way the op ones do. In your case, I would venture a guess that the sender wire is grounding somewhere.

 

i ran all new wires...

 

The wire from the sender goes directly to the gauge, the sender is the ground. It's a single wire system.

 

so on the gauge i have 2 post where do the wires run?
right now i have a positive wire from the battery and the other going to the sender.
it works but registers too hot, not reading the right temps.
like i say i am using all good known parts and have tried multiple combos with same results. something is not right with my wiring.

 

I haven't looked at the back of the cluster circuit board for a while, but doesn't the connections for the gauge come through the board itself? Other than a couple of plugs, most of the cluster inputs comes through the 2 round gang plugs. Each of the pinouts are listed in the FSM.

 

Temp wire from sender, (YW), goes to the round connector designated as C-01. It would need to be splied in there and not go directly to the guage.

 

yea i traced the wire from the pin through the circuit board. maybe there is something else in there it needs to function though.