Wiring on Rear of Speedometer.

An alchemy of sparks, copper wire and earth

Moderators: User administrators, Moderators

Post Reply
keynsham1
Registered user
Posts: 459
Joined: 27 Sep 2015, 06:41
80-90 Mem No: 0

Wiring on Rear of Speedometer.

Post by keynsham1 »

I am dabbling with the idea of fitting a GPS speedo in place of my original. I have found one I like and it fits well (in an old unit, not my own!!)


Image


However when I took my own dash cluster off, I notice there is a circuit board and ribbon cable connections to it on the speedometer. Early vans didn't have this. Does anyone know what the electonics are for? The speedo is analogue and driven by a cable and it is a manual with no cruise control so I cannot understand why there should be any electronics there at all?

Image

User avatar
Robsey
Registered user
Posts: 1451
Joined: 19 May 2012, 20:45
80-90 Mem No: 11137
Location: East Manchester

Re: Wiring on Rear of Speedometer.

Post by Robsey »

The L shaped circuit board strapped around the speedometer head is for the
Dynamic Oil Pressure System (DOPS),
or commonly known as the Buzzer of Doom.
This will have inputs from the charge light, 0.3bar and 0.9 to 1.6bar sensor, ground and rpm signal.

None of the inputs are for the road speed.

______________

There is a magnetic disc on the speedometer drive on a lot of clusters for water-cooled vehicles (including my basic 1983 van), which provides a speed pulse output.
My van does not have DOPS.

There are a few suppliers of the pulse pick-up, that clips into the speedometer head close to the reluctor ring.
Brickwerks used to sell one by GoWesty (USA).
(I think).
Last edited by Robsey on 04 Nov 2025, 14:26, edited 2 times in total.
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished

cobblers
Registered user
Posts: 920
Joined: 21 Feb 2010, 20:50
80-90 Mem No: 17450
Location: Derbyshire

Re: Wiring on Rear of Speedometer.

Post by cobblers »

It's for the 2 stage oil pressure "buzzer of doom" system - it has no connection to the speedo operation.

User avatar
ZsZ
Registered user
Posts: 1559
Joined: 12 Feb 2009, 16:28
80-90 Mem No: 14899
Location: Budapest, Hungary
Contact:

Re: Wiring on Rear of Speedometer.

Post by ZsZ »

As above, it is the oil pressure warning light electronics.

Some of the blue foil replacement PCBs have it implemented - the Gowesty one comes to mind, but I am not sure. Maybe the SHC has it too.
Zoltan
1986 Multivan ex-Caravelle. Van since 2006, running mTDi 1Z since 2008 with Fiat Croma 1.9 TDid pump 2008-2019, custom pump since 2019
5spd custom box 4.57 diff + 0.74 5th

davidoft1
Trader
Posts: 2967
Joined: 27 May 2009, 18:56
80-90 Mem No: 16628
Location: hayling island

Re: Wiring on Rear of Speedometer.

Post by davidoft1 »

It’s for cruise control apparently

cobblers
Registered user
Posts: 920
Joined: 21 Feb 2010, 20:50
80-90 Mem No: 17450
Location: Derbyshire

Re: Wiring on Rear of Speedometer.

Post by cobblers »

The little PCB that slots next to the speedo cable nipple?
It does cruise control and also controls the O2 sensor light on USA vans.
My Bluestar has something plugged into it, but it has neither cruise control nor an o2 sensor warning light.

Post Reply