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The wiring to my oil pressure sender finally succumbed to being "heavily oiled" and heat. Apparently the sender was not installed very tightly and leaked.
I've pulled the sender and the wires to the connector actually broke off during the removal.
I had a couple of questions my topic searches didn't turn up good answers for:
Can you actually separate the wired connector from the sender? I've pried a bit, but not terribly forcefully yet.
If I were able to remove the connector, can it actually be re-wired and re-used?
Is there a replacement option for the later model oil senders that use tab connectors or threaded nut?
At this point, I need an option that either allows me to rebuild a three post connector, or a two post option that I can wire directly. I'm open to proven options.
The connector will come off the sender. I use a thin plastic spatula to pop mine off. Unfortunately the connector is unobtainium separate from a factory harness (if they are available.) As Kevin said, replace with an earlier 2-pole sender and one of Sean's harnesses. By some miracle my plug was in good enough shape that I sent it to Sean when he made my new 14-pin harness and incorporated it. The three pin sender has a pressure sensor (transducer) and a pressure switch. My hypothesis is the factory didn't quite trust the digital dash so they incorporated a simple on/off pressure switch into the sender to drive the low oil pressure warning in addition to the digital dash analyzing the transducer signal and indicating low oil pressure as appropriate.
Sean's harnesses are extremely well made and a perfect fit. The wire colors are correct and the harnesses are covered with newer and better materials than original. All the connectors are correct except for the oil pressure connector which is NLA.
I have no affiliation other than being a satisfied customer who happens to live in the same 100 mile radius as Sean, but being a satisfied customer makes it easy to recommend harnesses made by Sean.
The three pin sender has a pressure sensor (transducer) and a pressure switch. My hypothesis is the factory didn't quite trust the digital dash so they incorporated a simple on/off pressure switch into the sender to drive the low oil pressure warning in addition to the digital dash analyzing the transducer signal and indicating low oil pressure as appropriate.
Thanks for that. I should have asked a lot earlier why one needed 2 and the other 3 wires.
The connector will come off the sender. I use a thin plastic spatula to pop mine off. Unfortunately the connector is unobtainium separate from a factory harness (if they are available.) As Kevin said, replace with an earlier 2-pole sender and one of Sean's harnesses. By some miracle my plug was in good enough shape that I sent it to Sean when he made my new 14-pin harness and incorporated it. The three pin sender has a pressure sensor (transducer) and a pressure switch. My hypothesis is the factory didn't quite trust the digital dash so they incorporated a simple on/off pressure switch into the sender to drive the low oil pressure warning in addition to the digital dash analyzing the transducer signal and indicating low oil pressure as appropriate.
Mike,
As I can tell the only difference between the two senders is that the 3 pin sender has a separately wired earth [the third pin] - why they did it this way I do not really know- perhaps they were somehow worried about a false earth. Either way on my motor I could not get the three pin sender to work despite replacing the engine bay wiring and a new 3 pin sender and eventually I bit the bullet and stuck a 2 pin sender in- works perfectly.
Quirky things these cars- a lot of what they did with the 928 is brilliant but not everything!
As I can tell the only difference between the two senders is that the 3 pin sender has a separately wired earth [the third pin] - why they did it this way I do not really know- perhaps they were somehow worried about a false earth. Either way on my motor I could not get the three pin sender to work despite replacing the engine bay wiring and a new 3 pin sender and eventually I bit the bullet and stuck a 2 pin sender in- works perfectly.
Quirky things these cars- a lot of what they did with the 928 is brilliant but not everything!
Hey FredR,
So what did you do with the common ground when you connected the two pin sender? Just tuck it away? And connect the red and green wires to the two pins?
So what did you do with the common ground when you connected the two pin sender? Just tuck it away? And connect the red and green wires to the two pins?
Stephen
Stephen,
You simply connect the output signals to the correct terminals as indicated on the wiring diagram and as stamped on the sender terminals and the common earth cable is just left where it is if it installed in the harness- it will do no harm. In my case I built my own harness without the common earth cable but did so after I had "proved the concept" with the earlier sender.
I still do not know what they changed the spec on the later models with that 3 pin connector that is NLA, not really reworkable and a sod to get off!
I still do not know what they changed the spec on the later models with that 3 pin connector that is NLA, not really reworkable and a sod to get off!
I suspect that the change was driven by ease of assembly at the factory, with virtually no chance of getting connections mixed up. The very fragile/delicate brass studs on the sender won't get broken during service with the later-style connection. The silicone boot on the later connection is less prone to corrosion and other electrical problems. Every once in a while, working on the car, I'm reminded that a lot of service and maintenance access engineering took a back seat to primary function and assembly concerns. Watching some TV features that show things like a whole dash being inserted through the driver's door opening and held in by a few bolts and a couple electrical plugs, I compare that with how not simple the same functions must have been for the folks still relatively hand-assembling our cars. It was done at assembly-line stations but still very labor-intensive. For the oil sender connections and the rest of the KS-2 front-of-engine harness, these were probably done with the engine sitting on the sub-frame dolly prior to marriage, maybe on the engine before it ever got there. The multi-pin connection had to be easier and more secure than having that particular connection with small nuts with the engine on a dolly. The multi-pin could be done with only one Hans.
I suspect but haven't measured to see that the connectors for the oil level switch have pins the same size as the pins on the later pressure sender. If so, I'd be tempted to try and cast those available connections into a silicone boot as part of the wiring harness, the way the original harness was done. Maybe the castable silicone used for molding acrylic pieces would be good for this. SeanR, GregB, Roger, how many late harnesses do you typically build at a time? ( = number of cavities needed in a mold fixture...)
I suspect but haven't measured to see that the connectors for the oil level switch have pins the same size as the pins on the later pressure sender. If so, I'd be tempted to try and cast those available connections into a silicone boot as part of the wiring harness, the way the original harness was done. Maybe the castable silicone used for molding acrylic pieces would be good for this. SeanR, GregB, Roger, how many late harnesses do you typically build at a time? ( = number of cavities needed in a mold fixture...)
I build them as they are ordered, 5 this week, one last week. The pins/connections are totally different between the 2 and 3 pin units. As far as trying to make something to work on the 3 pin oil pressure sending unit, in my opinion, it's not worth considering. The 3rd pin ends in a ground at the cluster and there isn't adverse things happening with it not being used.
I suspect but haven't measured to see that the connectors for the oil level switch have pins the same size as the pins on the later pressure sender. If so, I'd be tempted to try and cast those available connections into a silicone boot as part of the wiring harness, the way the original harness was done. Maybe the castable silicone used for molding acrylic pieces would be good for this. SeanR, GregB, Roger, how many late harnesses do you typically build at a time? ( = number of cavities needed in a mold fixture...)
Because Sean has Roger selling his harness, he probably makes more harnesses than I do and might not have the time to make "extras". However, I generally try to make 4-5 harnesses at the same time, so when someone wants a harness, I don't have to stop working on my "normal" work to build a harness.
I just "took over" building our harnesses myself...and made some changes to improve them, beyond what they were. It's now difficult to distinguish my harness frim the original Porsche harness, which is very important, to me.
I would really love to have the original boot with the three pins on the "late" harness, just for originality sake (and to save $100 buying a new sender with two connectors.) Additionally, I doubt that Porsche added that ground wire because they ran out of things to do and decided to build a new sender and a new loom.
08-27-2018, 09:04 PM
1991 GT Oil Pressure Sender - Replacement Options
