revs drop with the lights

[helga592]

Hi
Not the worse problem but the revs drop with the light on. Ticks over nicely 950rpm no problem, but when you turn the light on the revs drop just a little enuf i think to efect the flow of water round the engine as after 20mins or so the temp goes up a little. The volt meter says 14.6v and the amp gauge is fine. Should I worry as im not planing to site around in the dark with the light on and the engine running (1.9 water cooled DG)

[kevtherev]

coolant flow is greatly reduced at tickover so a spurious reading will ensue.
the alt is slowing the engine speed down although this only should really occur if the alt is trying to cope with a big power drain plus a battery near the end of it's life/poor earth.

[California Dreamin]

But if you do.....'sit around in the dark with your lights on' then as the temperature of your engine rises it WILL reach a point where the thermo switch will trip and the first speed on the radiator fan will cut in.....all pretty standard stuff and as it should be.
If on the other hand, your temperatures rises much past half way (certainly not 2/3rds) without the fan cutting in, then you have a problem with the rad fan/thermo switch operation. Usually a duff thermo switch TBH (5 minutes to change and about £14.00 to buy)

Martin

[ghost123uk]

14.6 volts, if at the battery is a little high, is that with the head lights on or off ?

[helga592]

Its 14.6v with everything off and drops to 13.4v when i turn the lights on. Like i said its not a big problem the van starts lovley and i ues it as my daily drive to work. I was more worried about the temp of the engine but i left the van to idel for 45mins today and the gauge went up to cover the LED and stayed there and the fan cut in so all seems ok.

[ghost123uk]

.

[Niander]

I always view it as good it slightly slows down ...means its charging...