speedo earth problem

[minijim]

Ive got a R reg diesel tourneo, The speedo works for approx 20 miles then stops usually the temp gauge also stops, Sometimes if you put use the foot brake or turn the fan on the speedo will work again but only as long as the brake or fan is used, I might also see the speedo flicker when the wipers or indicators are used. If the van is left for an hour or two or you do short trips the speedo is fine, Ive fitted a new earth from body to gearbox, changed the battery as at times its only just turned the engine over in the morning but I now think it could be a worn starter. Ive also replaced the radio / cd player to find lots of wires have had scotch locks fitted then removed at some time. Is there an earth on the back of the instruments

[doughythevanman]

I think it could be more alternator related? I would check the alternator and it wouldnt do any harm to check your earths to body, engine / box and give them a clean up and make sure they are secure.

[minijim]

Fitted extra gearbox earth, but speedo & temp gauge still stops working on a run. If use fan on full speed ( only speed that works ) or use foot brake speedo will work until fan is turned off or foot is removed from brake. Sounds to me like earth fault but where?

[AlanN]

I would take the clocks out and just make sure the plugs are fitting properly to start, there are 3 earths from memory, just trying to find my diagram from when I fitted Mondeo clocks... which Im sure are the same anyhow, seeing as loads of people fit them just to get the rev counter

Pin 7-black/yellow, pin 13-black, on the big plug and pin 4-black/yellow on the small plug

And Ive just checked that against Guy88 diagram aswel

[minijim]

Removed clocks, only 2 plugs one 16 pin & one 10 pin all look good .any ideas?

[AlanN]

No white corrosion in the plugs or anything... There are few earth points bolted up behind the dash, might be worth having a wiggle... Also make sure fuse holders are a snug fit...

Anyone with any other ideas

[minijim]

All looks good , clean & connections are tight & checked fuse box earth. Could it be a fault with the gearbox speedo sensor? You might be able to help with a second problem, The heater fan only works on 3rd speed , Ive bought what I think is a resister to get the other 2 speeds working any idea where I need to look for the old resister??

[trigger]

You can test the earth with a pen type test lamp, clamp the crocodile clip to a known live point and the pointed end probe into the earth pin on your clocks multiplug, if it lights you have an earth

[trigger]

All looks good , clean & connections are tight & checked fuse box earth. Could it be a fault with the gearbox speedo sensor? You might be able to help with a second problem, The heater fan only works on 3rd speed , Ive bought what I think is a resister to get the other 2 speeds working any idea where I need to look for the old resister??

Early models up to about 97 it's behind the drivers side headlamp, later models from 97 onwards it's under the dash

[minijim]

Its 1st reg Oct 97 Nothing behind the headlight, any idea where to look behind the dash? Speedo is working at the moment going on a run tomorrow so is what happens then.Thanks for your help.

[minijim]

Speedo up to its old tricks as it stopped working again after about 12 mile run, only this time it only came back on with the heater fan not the foot brake. Left the van for about one hour & the speedo worked again.