rev counter

[jimbogriff]

whilst driving along today , and randomly playing with the cockpit of buttons in my 300' disco .

i noticed somthing funny , if u pres the heated front windscreen on and off the rev counter drops by 750rpm for a small time :-
any one else notised this

jimbo

[Budgie]

As the rev counter is run off the back of the alternator then it could be a sign of something not quite right in there.

You'll be drawing extra current with the front screen on but it shouldn't affect the rev counter. :dunno1:

[Bush Tucker Man]

S'funny.
My tacho drops by a similar amount if I press the electric window switch to close them & they're already shut.

[si_guru]

My 'lights on' buzzer only works on Wednesdays - or so it seems!

[Snake da Sniper]

Originally posted by Budgie
As the rev counter is run off the back of the alternator then it could be a sign of something not quite right in there.

You sure? It should run off of the coil...

Screen heaters draw allot of current & so you might find that the revs drop slightly when you first hit the switch, but then the regulator in the alternator should sort out the inballance & provide enough charge to pick the revs up again..

This is all of course assuming that it's a petrol engine. :)

[Budgie]

Originally posted by Snake da Sniper


You sure? It should run off of the coil...

This is all of course assuming that it's a petrol engine. :)

See, I was assuming it was a 300 TDi Discovery that we're talking about (as Jim's profile says that he has one), which won't have a coil, and who's tacho runs off the back of the alterator. ;)

A common fault with the 300 TDi is for the connection on the back of the alternator (white & blue wire I think) to become loose and the tacho needle either starts jumping about or stays at zero.