Relay is loose -- it's screwed down through the firewall, I think.

There are two zigzag wires in the system, these get VERY hot (they are reisistor links).

To test the plugs themselves, check the connetors and then the voltage to ground at the plugs. There is a voltage chart in the manual, I'll look it up at home this evening (late) -- there is a fixed voltage drop for each element and for each link.

If you have voltage at the last plug, they are working. IF one is open or you have a grounded plug, they either won't work at all (no voltage past the open one) or the filament is shorted. Only way to check that is to pull them out to see.

I't's not unheard of for them to get crapped up with so much carbon from bad running that they short across the filament and don't heat properly. Can be fixed by carefull cleaning.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!