VDO oil pressure sender.

For all those wiring gremlins we love, this is the place to discuss them.

Moderator: Board Moderators

Post Reply
mudmover
Verified Poster
Posts: 12
Joined: Fri Sep 08, 2017 09:32
Model: Excel SE
Colour: Red
Year: 1990

VDO oil pressure sender.

Post by mudmover »

I have just fitted a 0-7 bar VDO sender which I purchased from Merlin Motorsport to my 1990 Excel SE. ( 0-7bar gauge) It looks identical to the old one.
Switching on the ignition produces a full scale deflection of 7bar. Changing the feed wire to the other terminal produces the same result. I get the impression that the sender may not be compatible.
Any help would be much appreciated.

User avatar
Hawaiis0
Senior Poster
Posts: 3272
Joined: Sun Jun 30, 2013 18:39
Model: Excel SA No 3
Colour: BRG
Year: 1986
Location: West Oxfordshire

Re: VDO oil pressure sender.

Post by Hawaiis0 »

Sounds like either a short or open circuit. I can never remember which way round they go.
Umm! What to do next?

Pete Boole
Senior Poster
Posts: 2412
Joined: Tue Apr 04, 2006 21:28
Model: Elite
Colour: Monaco White
Year: 1974
Location: Nottingham

Re: VDO oil pressure sender.

Post by Pete Boole »

I suspect it may be an earthing problem - is the sender fitted to the block? How many terminals does the sensor have? The gauge connects to the "G" terminal on the sender. The "WK" terminal is for the low pressure warning light.

Pete

User avatar
alanmoss
Senior Poster
Posts: 2054
Joined: Sat Mar 11, 2006 18:53
Model: Celebration
Colour: Marque Lotus Green
Year: 1991
Location: Burton, Staffs

Re: VDO oil pressure sender.

Post by alanmoss »

If the wire is not connected the gauge defaults to full.
Alan
Excel Celebration, 1999 Mini Cooper S, Dacia Duster 4x4

User avatar
Lotus-e-Clan
Senior Poster
Posts: 3980
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: VDO oil pressure sender.

Post by Lotus-e-Clan »

You may have been duped (unintentionally) by Merlin. :(

Happened to me a few years ago - I bought a 0 -7 bar sender off eBay which was described as VDO compatible.

Well it turned out NOT compatible with the 7 bar VDO gauge fitted to the Excel!

The so-called VDO compatible sender earthing profile off eBay was back to front and incompatible with the Excel. ie as the PRESSURE increased the duff eBay sender resistance DECREASED.

For the Excel the sender should have the opposite earthing profile: ie as PRESSURE increases the sender resistance INCREASES.
So if resistance approaches INFINITY then you have full scale deflection on the gauge.

And as pointed out by previous poster, if you disconnect the sender wire (resistance = INFINITY), then you get full scale deflection at the gauge.

Because your sender has HIGH resistance with ZERO PRESSURE then you will see full scale deflection with the ignition on when the sender is connected OR disconnected. If you start the engine then the gauge PRESSURE might DROP - IF what I have proposed is true for you.

I still have the incompatible eBay 7 bar sender in my tool box - unused. I bit the bullet and paid a hell of a lot more for a proper one from SJS. I doubt if they have any left mind you.
Last edited by Lotus-e-Clan on Mon Nov 30, 2020 22:51, edited 2 times in total.
Peter K

User avatar
Lotus-e-Clan
Senior Poster
Posts: 3980
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: VDO oil pressure sender.

Post by Lotus-e-Clan »

If you are revisiting this thread please note that I've edited my previous post 'cos I wrote temperature when I meant pressure! :oops: Getting senile.... :(
Peter K

mudmover
Verified Poster
Posts: 12
Joined: Fri Sep 08, 2017 09:32
Model: Excel SE
Colour: Red
Year: 1990

Re: VDO oil pressure sender.

Post by mudmover »

Many thanks for all your inputs.
So far:
1. Checked gauge, returns to 0 when earthed.
2. Gauge has 2 unmarked terminals.
3. Get full deflection of gauge using either terminal.

I note from a VDO website that they produce senders with both G and WK(warning light) terminals, and also with G and M(earth) terminals. I assumed the spare terminal on the new sender was WK, - perhaps it is M ( earth ).

4. Fitted feed wire to sender and also fitted earth wire to second terminal. Gauge returns to 0 and on starting engine, indicates oil pressure.

Confused of Cornwall!

Pete Boole
Senior Poster
Posts: 2412
Joined: Tue Apr 04, 2006 21:28
Model: Elite
Colour: Monaco White
Year: 1974
Location: Nottingham

Re: VDO oil pressure sender.

Post by Pete Boole »

Well done! Don't know why they make so many different senders!

Pete

mudmover
Verified Poster
Posts: 12
Joined: Fri Sep 08, 2017 09:32
Model: Excel SE
Colour: Red
Year: 1990

Re: VDO oil pressure sender.

Post by mudmover »

Just re-read my post, - it is the SENDER which has 2 unmarked terminals!!!!

Even more confused of Cornwall, - I'm getting a headache!

User avatar
Lotus-e-Clan
Senior Poster
Posts: 3980
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: VDO oil pressure sender.

Post by Lotus-e-Clan »

mudmover wrote:
Tue Dec 01, 2020 17:59
Just re-read my post, - it is the SENDER which has 2 unmarked terminals!!!!

Even more confused of Cornwall, - I'm getting a headache!

I know how you feel! :lol:

BTW I used to live just outside of Truro. Whereabouts are you?
Peter K

mudmover
Verified Poster
Posts: 12
Joined: Fri Sep 08, 2017 09:32
Model: Excel SE
Colour: Red
Year: 1990

Re: VDO oil pressure sender.

Post by mudmover »

Lelant,- just outside St Ives.

Pete R

User avatar
Lotus-e-Clan
Senior Poster
Posts: 3980
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: VDO oil pressure sender.

Post by Lotus-e-Clan »

mudmover wrote:
Wed Dec 02, 2020 11:37
Lelant,- just outside St Ives.

Pete R
Aha! The double mini roundabout just outside Lelant by the A30 drives me up the wall ..folk get confused on priority.

We are still regular visitors to St Ives. Tend to stay at Travalgan touring park in the Camper but also cottages in Downalong when we've taken the Excel (park it on Smeaton's Pier).

We're in a bit of bother at the moment because 18 months ago we booked for the Christmas week 2020 in a cottage next to Smeaton's Pier but we don't know if we will be allowed to honour the booking.

Won't be much good if the pubs and restaurants (or St Ives residents) don't want visitors mind you. If we're allowed go it's a toss-up between Lotus or Camper...Camper tends to be better on winter roads mind.
Peter K

mudmover
Verified Poster
Posts: 12
Joined: Fri Sep 08, 2017 09:32
Model: Excel SE
Colour: Red
Year: 1990

Re: VDO oil pressure sender.

Post by mudmover »

If you are down this way, give me a shout
Regards,
Pete R

User avatar
Lotus-e-Clan
Senior Poster
Posts: 3980
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: VDO oil pressure sender.

Post by Lotus-e-Clan »

mudmover wrote:
Wed Dec 02, 2020 13:31
If you are down this way, give me a shout
Regards,
Pete R
Yeah Cheers. I'll show you my Evans cooling mods ....you'll soon glaze over though ...most do! :lol:
Peter K

Post Reply