FredR

Today I pulled the 3 pin sender. As Stan said not much oil came out and I had to undo it with the 24mm wrench only as there was no room to counter hold the module that holds the relief valve. Monitored it carefully and the sender came out quite easily with no movement of the holder assembly [otr whatever it is called].

Tested the 3 pin sender and to my dismay, it seems to be working perfectly. I ave not tested the new 2 pin sender installed so logically I should do that but now I am feeling somewhat down as I have no idea what to do next.

To summarise-
1. The gauge pegs at full scale when the ignition is turned on.
2. When the motor starts theindication behaves as normal.
3. Occasionally the gauge seems to stick at about 3 barg independent of revs.
4. Switch the engine off- the gauge drops and as it approaches zero it suddenly flicks over to full scale and stays there.
5. After a few hours like that if I tap the display it will sometimes drop to zero.
6. Disconnect the battery the needle stays at full scale
7. Earlier I tried the display unit from my late S4- does exactly the same.
8. Cables from 14 pin connector to sender are new and pins connected correctly

When my spare display units are stored the needle is on zero- no voltage no movement so why is my display going full scale/what can cause this to hold there if there is no power on the car?

I dare say there could be something wrong in the wiring between the 14 pin connector and the display unit but so far I cannot find anything that seems untoward.

kmascotto

Fred, it would seem there is a power bled from another circuit (Like the xbus) or something that is energized after the car is shut off. As it is always said..."what was the last thing you did before it started working this way".

That... or the dam thing is possessed

FredR

Kent,

The damm thing is full scale when the battery is disconnected and then there is no power from anywhere so as I can tell with my meagre electrical skills it should return to the power off position if there were some kind of false cross connection but it does not do this.

Hopefuly tomorrow I can test it with the 2 pin sender in situ but I doubt that will make a difference given today's result.

FredR

Today I fitted the two pin sender, fitted some spade connectors to the two terminals needed and then turned on the ignition- shock- horror- the needle twitched slightly and sat at zero! Fired the motor up- needle went to full scale, turned off the motor and the needle droped as the oil pressure declined and settled back at zero- bingo!

I am still baffled as to what was causing the problem but I rather suspect there must have been an earthing problem of some kind given the VDO gauges for some reason sem to peg out if they are not eartheed correctly. Perhaps there was some kind of issue between the 14 pin connecor and the dash but if so that seems a bit strange given the display worked more or less ok most of the time.

Whatever the reason I will gladly take it. So much for 3 pin senders and their NLA connectors!

Rgds

Fred

Mrmerlin

I was just as baffled when I put in my new sender and the gauge worked as it should

FredR

Stan,

If it was enough to baffle you then no wonder I have been baffled by it. Seems that throwing in the towel and buying the two pin sender was a good move.

I even managed to get the alternator back on without too much grief- nowadays I simply jack it into position using a scissor jack. I was a bit concerned that trying to get the bolt back in with the lower hose in-situ might complicate matters but that did not happen. The trouble with working from jack stands on things like that is getting enough leverage to push it into position- probably not an issue if one is working under a lift.

Now all I have to do is sort out why my tach signal breaks down at 5k+ rpm's!

Rgds

Fred

Taguid

Let us know if you get that tach problem fixed because mine starts to bounce around 5k too.

FredR

TRacy,

Given the problem on the oil gauge may be an earth related fault in either the display or the wiring to it I am wondering, given VDO make the job lot, if some similar problem is taking place is ocurring in the tach. i had exactly the same issue with my late S4 albeit the symptoms are not exactly like those the oil pressure gauge exhibited.

Hopefully someone will have osme bright suggestions- never managed to sort it out on my S4.

Rgds

Fred

FredR

Got to take the 928 for a spin this afternoon. Initially it seemed as though the gauge was fully pegged as in at fault but as the motor fully warmed the indication settled at exactly 5 barg at about 2800 rpm- perfect! At idle it dropped to an indicated 2 barg again perfect.

A 5.00pm the ambient temperature was down to a balmy 32C the motor ran sublimely. Logic says it should not feel any different but it- placebo effect? Ever since I acquired this 928 and put my S4 motor into it the oil pressure oil ran to an indicated 4.5 barg and that with both 3 pin senders I used. Idle would be 2 barg dropping to 1.5 barg on really hot summer days but the needle response to engine movement was "sluggish". Now the needle follows the revs pretty crisply.

Just seeing a full 5barg must have an impact on the grey matter placebo or not! It felt like I had suddenly got my old motor back in the car!

Rgds

Fred