axis of evil

Dead transmitter, and looking to fitting aftermarket, does anyone know the OHMS of original, so I can have the factory gauge running accurately. Car is 1982 model.
thanks

IcemanG17

typically when the oil pressure gauges fails, its due to a dead "pressure sender" near the oil filter...the standard mode of failure is to peg at 5+ bar too

karl ruiter

Don't know the answer to your questions (although I am interested), but you can get the stock sender off ebay for pretty cheap.

karl ruiter

You could always aligator clip some resistors in place of the sender and see how the gauge responds. Give you pretty good idea, if nobody knows.

UncleMaz

Not sure if it is the same p/n, but the 944 VDO sender operates as such:
1 bar - 29.6 ohms
2 bar - 65.3 ohms
3 bar - 98.9 ohms
4 bar - 133.6 ohms
5 bar - 184 ohms

Also, you can ground the lead at the sender and have someone watch the gauge. If it pegs, with ignition on, it is the sender.

depami

I currently am fighting pressure sender issues on my 82 five speed. The original had a broken terminal so I got a replacement from PP. I went for the $35 after market instead of the $95 Porsche.

I hooked both old and new to an air compressor and checked with an ohm meter.

At 0 PSI the light connection was closed and opened at 15 PSI on the old and 20 PSI on the new. It remained open to 135 PSI, the maximum I could produce.

The gauge connection showed 50 ohms on the old and 25 ohms on the new at 10 PSI.

At 100 PSI the old read 210 and the new read 220. They were both linear in between.

I then connected a potentiometer to the gauge wires on the car. I started at 0 ohms and slowly increased to one bar on the gauge. I then disconnected the pot and measured it.
Here is what I got: 1 bar = 10 ohms, 2 = 40, 3 = 70, 4 = 100, 5 = 160.

I also hooked a mechanical gauge to the car and to my surprise, it read 130 PSI at fast idle with old oil. After dropping to normal idle it read about 90 to 100. 5 bar is about 75 PSI.

After driving the car till warmed up, with fresh 15/50 standard oil, it is pegged at rpm and drops to about 3.5 at idle.

The problem I still have is that every now and then the light comes on. When it does I check the sender and the light connection is closed even though the gauge shows good pressure.

I tend to believe the gauge and not the light. I may call PP and see if they’ll give me credit toward the more expensive Porsche sender as I believe the “cheap” one has a problem.

Hope this helps someone and thanks in advance on comments about my issue.

depami

karl ruiter

Take the bulb out of the light and keep an eye on the gauge?

axis of evil

Thanks for all the information, Was only going aftermarket because Local (Australia) dealer quoted $200+ , Will try an aftermarket from US ebay, BIG saving,(didn't think to look there.)

SharkSkin

FYI, I posted info on the sender about 6 months ago, post #10 here. Not far off from the numbers Micheal posted.