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        General >> Problems >> Tacho
        
(Message started by: DaveN on Feb 22^nd, 2006, 7:39pm)

Title: Tacho
Post by DaveN on Feb 22^nd, 2006, 7:39pm

Hi Folks, anyone know how the signal that drives the tacho is derived on a 2.9 12V? mine is dead and the pulses reading shown in the instrument diagnostics is 0?

Title: Re: Tacho
Post by Eric_R on Feb 22^nd, 2006, 9:02pm

Dave,
The speedo is driven by the Vehicle Speed Sensor, (VSS) mounted on the side of the autobox. It is simple to change, see
http://www.fordscorpio.co.uk/manual/electrical/intbasic/VSS.pdf

Your A4LDe gearbox is less sensitive to the loss of the VSS input, but you may have noticed that the engine isn't changing up properly into 4th and the torque converter lockup may not be working. This will correct itself as soon as the EECIV gets the correct VSS input.

HTH

Title: Re: Tacho
Post by DaveN on Feb 23^rd, 2006, 1:47pm

Thanks for the info, I thought perhaps it wasn't the VSS as the car runs smoothly with no gearbox problems that I know of and the speedo works fine. The tacho refuses to budge from 0 but the needle kicks when reset, should't I get some reading from the pulses readout in the diagnostics - any more thoughts would be appreciated..

Title: Re: Tacho
Post by Snoopy on Feb 23^rd, 2006, 3:48pm

AKAIK the tacho on the 12v is pulse driven from the coil

Title: Re: Tacho
Post by DaveN on Feb 23^rd, 2006, 7:09pm

Cheers for that, maybe it's a bad connection somewhere in between then as the engine runs ok. Does it comes via the ECU rather than straight off the coil?

Title: Re: Tacho
Post by Snoopy on Feb 24^th, 2006, 7:28am

does this link help at all http://www.carsoft.ru/avtorepair/sierra/incl.pdf

Title: Re: Tacho
Post by DaveN on Feb 24^th, 2006, 1:23pm

Thanks for the link, I've printed off the schematic (all 12 pages) - just need to put my thinking head on... next question "where did I leave it?" -

Title: Re: Tacho
Post by david_molloy on Feb 24^th, 2006, 7:55pm

Don't want to state obvious - but have a similar problem myself with abused Scorp which I bought for spares.
Rev counter doesn't budge on 1st start up - even "blipping" throttle has no effect - appears stuck.
In my case easily solved by banging fist on top of dash above rev counter.
Once read about someone else doing same - carn't remember where - as I commented that just like old TV fix 30 yrs ago.
If it doesn't work - bang it - does actually work sometimes!!!.
Once rev counter working - fine for day & rest of start ups - sticks again overnight!!
david

Title: Re: Tacho
Post by DaveN on Feb 25^th, 2006, 9:15am

Tried Thumping it to no avail and have since realised that the cruise control also doesn't work so gave the button a bash as well..that hasn't helped either..should I hit anything else! - cheers

Title: Re: Tacho
Post by david_molloy on Feb 25^th, 2006, 11:35pm

Looks like thumping not solution in your case.
Suspect that cc problem may be relevant
I haven't got cc - so no experience
Best of luck
david