I have a 2002 Jetta, 1.8L Turbo. A mechanic replaced the oil pressure sensor with an oil pressure guage. The guage works fine, however without the sensor connected the warning buzzer and dashboard light for low oil pressure are constantly active. If I ground the one wire (green) that was connected to the sensor will that deactivate the buzzer and light and without negatively impacting other electrical components that may be connected to that wires network.
The first question is why did your mechanic do this instead of just replacing the sensor like a normal mechanic, and why aren’t you telling him to fix the problem he caused?
We had just had the sensor replaced by another mechanic. We were on the road, several hours from home. We suspected that the new sensor was the problem, rather than actual oil pressure, but were rather panicked about the possibility that there was an actual oil pressure problem. We’d been on the phone with the first mechanic, and with a relative who mentioned the value of mechanical oil pressure gauges to assess what’s really going on. At the second mechanic (people we knew and trusted) they determined that the oil pressure was fine. We also found an almost broken wire that indicated that the problem was not the sensor itself but its connection. But the part we’d have to replace to fix the connection (some kind of harness, I think) would have taken days to order and we were in the middle of nowhere, it was getting dark, and we needed to get to our destination. The manual gauge (which he was able to obtain quickly) allowed us to get to our destination being sure the car wasn’t about to die. We thought it would also give us more detailed and trusted information about what was going on with the oil.
How about putting in a “T” and have both the gauge and the warning light/buzzer? That way no re-wiring/disconnections are needed. That’s what I would do.
That’s what I’d do too.
I also wonder why if the mechanic was willing to hack in an oil gauge and send the customer off with a buzzer going, he wasn’t similarly willing to just splice in a patch to the broken wire, but road trips leave us vulnerable to weird random acts of mechanics.
Yes. Standard procedure would be check oil level. Remove sensor and check oil pressure with manual gauge. If oil pressure was acceptable replace defective sensor. When the damaged wire was found I would have spliced it (if possible) as a temporary repair.
Have you tried jumpering the sensor plug?
As near as I can tell the OP now has a new sensor and no longer has a problem. That should solve the buzzer problem. Not sure what else the OP needs to get advice about.
Thanks for your reply. The mechanic and I were thought the problem may be caused by a cut in the insulation of the wire that connects to the oil pressure sensor (switch). The cut was very close to the connector, such that splicing in a new piece of wire (patch) was not possible. The mechanic would have had to acquire a new connector with a longer pig tail wire [not sure what to call it] from a distant VW dealer. A quick solution he had available was to remove the electrical sensor (switch) and replace it with a mechanical pressure gauge.
Thanks for your reply. I am not sure what you mean by ‘jumpering’ the sensor plug.
[quote=“edcycles, post:9, topic:102417, full:true”]
Thank you for your reply. The cut was very close to the connector, such that splicing in a new piece of wire (patch) was not possible. The mechanic would have had to acquire a new connector with a longer pig tail wire [not sure what to call it] from a distant VW dealer. A quick solution he had available was to remove the electrical sensor (switch) and replace it with a mechanical pressure gauge
[/quote] So now I have this mechanical pressure gauge that I like because it gives me more information than would the factory installed sensor (switch). But, as there is no sensor installed the car’s electrical system is not getting a signal from the sensor that all is well, hence the annoying buzzer. My original question remains, ‘if I ground out the wire that had been connected to the sensor will that stop the buzzer - AND, do so without causing other electoral problems.’ I attempted to get and answer to this question from the VW dealer where I have taken the car for maintenance in the past (they were not involved in any of the work with this issue). They did not have an answer (or want to give one - other than bring the car in and throw a lot of $$$ there way). I tried contacting VW company - but they only seem to have communication pathways open for potential new car buyers.
Connect the two prongs of the sensor’s plug together with a wire to simulate the switch in the sensor being closed.
OP has a failure of the factory, electrical oil pressure gauge, and somebody plumbed in a mechanical oil gauge with a Bourdon tube. While OP is satisfied oil pressure is A-OK, the car’s ECU still “thinks” that he has zero pressure, and has lights/buzzers going off. He wants to know how to disconnect.
That sentence had me confused. I guess that was before the pressure gauge was installed. So my earlier post was wrong.
OK, yes, of course, ‘jumper’ across the switch. And, my wife just found and handed me two little alligator (jumper) clips with a wire attached. So now I can give that a try. Also, you have me thinking that since there is only one wire that was connected to the pressure switch it probably grounds out (with switch closed) through the switch body’s threads that connect it to the engine port. Hence, my initial idea to ground the wire should work without killing other (interconnected) electrical warning systems. Somebody, please stop me if my understanding of the electrical logic of this switch is incorrect and what I am about to do is a big no no.
Yes, a local mechanic put in a new pressure switch, and a couple days later while on a long distant road trip the warning buzzer went off. The oil level was good and per (road trip) mechanic, the oil pressure was good. It was then that we noticed the break in the wire sheathing and presumed that was the cause for the switch sounding the buzzer.
Thanks for the clarification. Yes, your comment succinctly describes the current status of this oil pressure buzzer adventure.
To answer your question, just use the alligator clips to ground the wire. I ran that way for quite a few years when my coolant level sensor got gunked up and kept telling me the coolant was low. I just used a heavy clip on the oil cooler pipe to create the ground. Worked fine and the light stayed off.
So the original problem was likely the cut wire and not the sensor. So suit yourself, fix or not, but the clip should work.
Thanks to you all who provided input to a solution. This AM, I grounded the wire that had connected to the pressure sensor, using an alligator clip and pigtail arrangement. While doing so I got a closer look at the wire and found it was indeed damaged (quite a few wires in the braid were broken). The good news is that the oil pressure buzzer is no longer coming on (at least not as of yet) and the grounded wire does not appear to have compromised any other electrical components. Thanks again to the Car Talk community for your assistance. --Edcycles
Just one further question. Is this mechanical oil pressure gauge the type that uses a nylon pressure line to the gauge or is it all electric?
The former can work fine; it’s just that the possibility exists of a line cracking apart over time due to age, vibration, and hot oil. That means hot oil will be dumped at the site of the opening; even inside the car.