Webasto fault finding

[davegsm82]

I'm not sure if the Webasto has the same basic circuitry as the Eberspacher D3LC but it might have a similar problem to what mine had.

There is a relay which provides power to the Glow plug, so +ve goes into the control box, then from the control box to the Glow plug, then from the glow plug it goes to a transistor mounted in the body of the Eber iteself, on mine the Relay was sending +ve to the plug but the transistor wasn't switching on properly and as such the glow plug wasn't heating up enough.

The secret is to measure voltage ACROSS the glow plug, don't just assume that one side of it is connected directly to ground. The Eber glow plug has 1 nut holding the wires on but there are actually 2 connections being made, in and out. This completely threw me off the scent when I was trying to fault find.

Also, with regards to plug resistance, because the plug resistance is really low (less than an ohm) your multimeter probes may mislead you into thinking it's higher than it actually is. before you make a resistance measurement, connect the multimeter probes together and see what the meter reads, it may be up to 0.5 Ohm. This is the Static resistance of the Meter and cables, once you make your measurement of the plug then you need to subtract this number. i.e. if your meter reads 0.4 with leads shorted together, and you read 1.2 ohm on the plug, then your plug resistance is actually 0.8 ohm.

Dave.