boxsey911

I've just replaced my oil pressure sender with a new OEM one and now the oil pressure gauge needle is pegged to the top (above 5) and the oil can warning light on. All other oil gauges are fine.

I checked the orientation of the sender both before and after changing it and I'm sure I connected it up correctly. In fact the two spade connectors are different sizes so it's not possible to switch them by accident.

Is there a fuse for the oil pressure sender I should check first? (I didn't bother disconnecting the battery while changing the sender as I assumed the wires were not live without the ignition on).

Or is it possible that the spades on the sender have been put on the wrong terminals and swapping them around will solve the problem?

Or have I just bought a duff new sender?

Rocket Rob

Did the gauge work properly before the pressure sender failed? It sounds like the two wires on the pressure sensor are backwards. When I bought my C2 a few years ago, its oil pressure gauge did the same thing. When I dropped the engine to do some repairs and replace the clutch, I checked the wiring, the wires were backwards.

Its easy to tell which wire is the gauge wire and which is the oil pressure light. With the wires off the pressure sender, turn on the ignition and then ground one of the wires. It will either cause the oil pressure light to come on or it will peg the oil pressure gauge. Then check that the other does the opposite. Once you know which is which, then attach to the pressure sender.

boxsey911

Thanks Rob. Yes it worked before but the needle used to flick about at idle and it was recommended by my tech to put a new one in.

As I mentioned above the spade connectors are different sizes so it's not possible to reconnect the wrong way round (i.e. the small female spade on the red/green wire won't fit on the large male spade on the sender). Hence, I'm wondering if the male spades on the new sender have been put on the wrong terminals. I'll do your check so I know which wire is which but is it possible to tell which terminal on the oil sender is for the gauge and which is for the warning lamp?

p.s. I have the old sender still and can put that back in but I'm now faced with tearing our the inlet again to get to the sender

Rocket Rob

Perhaps VDO changed their design of the pressure sender. I had to change the spade connectors on the wires to get them to fit on the proper terminals. I figured it was an odd thing to do but maybe I'm not the only one.

boxsey911

Just checked the fuse box and there's nothing listed for the sender so it looks like tomorrow's job is to investigate further. Luckily I didn't junk the old one (not that I ever junk anything to do with the '64 ) so I can use that to help solve the mystery.

boxsey911

Well it looks like the new sender was duff. I tried swapping the terminals over but not joy. I've put the old, flaky sender in for the mean time while I wait for a replacement.

For information: with a sender that's good the gauge needle will shoot to the top when the ignition is turned on prior to firing up the engine. It wil then read pressure once the engine is fired. With a duff sender the needle stays at zero with just the ignition on and then pegs itself to the top once the engine is fired.

ppashley

I had problems with an OP sensor on my 993.
Make sure you spend the extra $$s on obtaining a replacement sender from the dealer (directly). Thi
I bought some so-called OEM senders on the grey market, and ended up sourcing one from the Dealer. (after advice from others on RL). That sorted the issue, and in this case buying from the dealer was the way to go.

GL

Phil

boxsey911

Looks like you are spot on about this. I've just installed a second aftermarket sender that was sent in replacement and it worked for a few seconds before pegging the needle to the top again . So it looks like getting an original part from Porsche is the only way to go with this one. Hopefully, I'll be lucky the third time and I should now be able to remove and replace it in record time .

bawmnot

Hi Boxey, I have coincidentally just had a new sender installed for pretty much the same reason as you - the old one was acting a little strangely. The first replacement was duff - pegged to 5 in exactly the way you describe. 2nd replacement works fine so far. Seems like there are a few rotten senders around. I don't know whether the new senders the mechanic used were OE or OEM.

bawmnot

Driven the 964 a couple of times since I wrote this and the oil pressure warning light is now coming on - so far on an engine restart when hot, but also when idling at traffic lights. It only comes on for a few seconds and goes off when I put the revs up.

Oil lights frighten me - even though some threads on this issue say occasional warning light at idle when engine hot is nothing to worry about. Would I be foolish to keep driving the car with this going on?

Boxey - did you get round to installing the OE sender unit, and is it working OK? I am tempted to order a sender from the dealer and install, just in case it's the OE sender ercently installed which is the source of this problem.

Cheers, Andrew.

boxsey911

Andrew, I'm picking a new sender up from Wilmslow Porsche Centre on Saturday and hoping to have time to install it at the weekend. With the two new supposedly OEM senders the gauge was pegged to the top (higher than 5) and the oil can light (and exclamation warning light) comes on and stays on. The one from Porsche I'm getting is twice the price .

boxsey911

I'm pleased to say that the 3rd sender I purchased (this time from Porsche for £73) is fitted and worked perfectly. Below is a pic of all the senders; left is the original one that works but the gauge needle bounces around. The middle one is the 2nd aftermarket one made by URO and although the correct original part number didn't work at all. On the right is the Porsche one which is made by VDO and has a later part number (ends in 04 instead of 01).



I would say the big lesson I learned here is to only purchase something like this from a non Porsche parts dealer if the part is a true OEM part (i.e. in this case it needs to be made by VDO).

bawmnot

Good call boxey. I'm in a similar situation, though my aftermarket replacements were both by FAE. - first one didn't work, second one has jumpy signal at idle, resulting in occasional oil pressure warning light. I'll be fitting a VDO part then! How long did it take you to swap? - I've little mech experience so far on this car, but from the write ups I can find it's not too tricky a fix?

boxsey911

Most of the time is taken up by taking off the inlet manifold. Now that I've done it three times it only takes me about an hour

If you've got a spare weekend day you're welcome to bring it over to my place and I'll show you how to do it. BTW if you haven't replaced the O ring on the sender housing, get one of those too and do it at the same time (about £1 for the part).

tfitch03

Sorry to revive am old thread but anyone know what would cause my oil pressure gauge to peg itself at max all the time? Just started this afternoon. Normal operation before this, I pay close attention to it.