Practically Classics Forum

OK it ain't a classic..Mines not working . It's got juice going to it , i put a bulb between the cables and it lights up. I put the bulb in series with the screen , and it lights up. None of the elements are damaged . But it doesn't demist at all.. not even a little bit . Now i know they drag a lot of current ,if i get a second battery and hook it up to the screen lucar connectors with a jumper cable , would i expect to see it arc ? It's a T4 van , so the cables from the relay plate are pretty long ... thinking maybe volt drop ? How many volts ought there be at the screen when its on and the engines running ? 13. ? something ?

Hmm.... Don't these vans rely on studs that make contact when the door's shut rather than wires going inside the door? These have a nasty habit of developing just enough surface corrosion to prevent enough current passing for screen clearing purposes. Try a scoosh of Halfords (or WD40 brand, but theirs is twice the price and not twice as good) contact cleaner and wipe with a soft cloth, don't be tempted to use abrasives though, that'll compound the problem in the longer term.

Nope , cables are in a grommet , and my light bulb (in parallel with the screen ), is lit when the tailgate is shut, (on all the way home tonight ..) so there can't be a cable fracture.. Hey ,if it was nearly fractured...just a few strands left..would it then be like a fuse and the cable get hot rather than the screen? It hasn't worked for over a year ,so i would have thought it would have totally fractured by now,or burnt out if that was the case , tailgates up n' down all day long..

This test is the same as my problem , though my connections are good it still won't work . I tested it the same way . http://www.youtube.com/watch?v=tny-8wGGcw4

How do i measure how many Amps are going through the cables to the screen? The engine stays the same revs when the screens turned on .Headlights on switch lower the revs a tad..

If your multi-meter has an amp function then set it on 20a and plug it in series with the heater and see how many amps it draws. If you are getting no demisting then my suspicion is none. Have you got much resistance across the heater itself?
The front screen on my RR is suffering with a similar problem but I haven't bothered investigating yet (largely as I have to take the scuttle off to get at the connectors which is a pig of a job so I can't be bothered).

I've only got a 10 amp facility on my gadget , i think it will just trip out if i do overload it , so i'll try it in series .I attained A in o level in Physics , i should remember
Yes, there is resitance on all the elements.. and mist on the screen

Check the resistance figure between the element and the door, there has to be a poor connection somewhere and if it's not supply then that only leaves earth.

I've just read this http://www.pistonheads.com/gassing/topic.asp?t=953614 and i'm trying to remember physics lessons , so if i've got a higher resistance elsewhere in the HRW circuit (other than the screen itself ) like a poor connection ... my screen ain't gunna work , that right ?? I'll check the tabs on the screen tomorrow , the 9v battery in the tester has gone flat now. It's telling me i've got a 19.6 volt battery on the van !!

zipgun wrote: so if i've got a higher resistance elsewhere in the HRW circuit (other than the screen itself ) like a poor connection ... my screen ain't gunna work , that right?

That sums it up, yes.

Reeet. Thanks.