L322 Heated Windscreen issue - Only Passenger side works

Walshie1987 · Nov 24, 2018

Hi all,

Sorry to raise this again but I've done some more testing this morning and wondered if anyone with any knowledge could advise? The first thing I noticed is that the pillar cover has been off before - suggesting someone has attempted a fix before.

I've tested the volts to the screen - all good - reading was 13.38v when switched on, 0v when switch off. So this rules out fuses / relay.

Tested resistance of screen - appears good. Resistance is there 126kohms (if I setup the multimeter properly - it's from the 90's so every chance I didn't - but there was resistance)

This is the bit that's I really need advise on:

There is a third wire connected to the screen, in which a single positive wire goes into it. From the wire that goes into it I can't get a volt reading off this at all. I've done a continuity test on the windscreen connection to see what it's connected to and it appears to be connected to other live connector on the second (bigger) windscreen connection - there is very little / no resistance between these tow connectors. (The attached picture may chow this a little cleared - the 0 is the resistance test, so shows the connectors are joined and offering little/no resistance).

Any help would be appreciated as ever

Cheers
Cheers

tomcat59alan · Nov 24, 2018

Dopey said:
Or.... you could do what some dirty rascal did, hit the screen with a rubber hammer, and tell the insurance you hit a pheasant on the motorway... so I have been told that is...

Can I have my hammer back if you've finished with it please.

Datatek · Nov 24, 2018

Walshie1987 said:
Hi all,

Sorry to raise this again but I've done some more testing this morning and wondered if anyone with any knowledge could advise? The first thing I noticed is that the pillar cover has been off before - suggesting someone has attempted a fix before.

I've tested the volts to the screen - all good - reading was 13.38v when switched on, 0v when switch off. So this rules out fuses / relay.

Tested resistance of screen - appears good. Resistance is there 126kohms (if I setup the multimeter properly - it's from the 90's so every chance I didn't - but there was resistance)

This is the bit that's I really need advise on:

There is a third wire connected to the screen, in which a single positive wire goes into it. From the wire that goes into it I can't get a volt reading off this at all. I've done a continuity test on the windscreen connection to see what it's connected to and it appears to be connected to other live connector on the second (bigger) windscreen connection - there is very little / no resistance between these tow connectors. (The attached picture may chow this a little cleared - the 0 is the resistance test, so shows the connectors are joined and offering little/no resistance).

Any help would be appreciated as ever

Cheers
Cheers

126K ohms, not checked one but I wouldn't expect to see more than about 200 ohms, what you have is virtually an open circuit. The must be 3 wires to the screen, LH positive, RH positive and earth, possibly 2 earth wires.

Walshie1987 · Nov 24, 2018

Ah sorry, just checked it was ohms not K ohms.

So that seems normal too?

Cheers
Chris

Datatek · Nov 24, 2018

Walshie1987 said:
Ah sorry, just checked it was ohms not K ohms.

So that seems normal too?

Cheers
Chris

Just done the sums, that still sounds high. With the wires connected to the screen and the screen switched on, what voltage do you have each side between the positive and the screen earth point?

Walshie1987 · Nov 24, 2018

Just going to measure again now, thanks for this

Cheers
Chris

Walshie1987 · Nov 24, 2018

Almost nothing at all

Walshie1987 · Nov 24, 2018

But when I test like this and turn on I get 13.5v on the single wire

Datatek · Nov 24, 2018

Walshie1987 said:
But when I test like this and turn on I get 13.5v on the single wire

So with no load you have 13,5 volts but as soon as you apply the load you have no volts. Therefore either the relay, fuse fuse box or connection to the fuse box has a high resistance connection. For starters, swap the relay.

Walshie1987 · Nov 24, 2018

Here's the ohm reading on my prehistoric multi meter, between the positive and earth on the RH side

Datatek · Nov 24, 2018

Walshie1987 said:
Here's the ohm reading on my prehistoric multi meter, between the positive and earth on the RH side

That is meaningless, you cannot test with ohms to earth in the situation you have.

Walshie1987 · Nov 24, 2018

Sorry, so no load when switch off on any wires.

When unplugged 13.5v on the double connector positive, nothing on the single wire.

When plugged in, and switched on, 13.5v on the single wire, 0v on the double connector.

I think they are all driven off 1 relay in the l322?

Will try the basics like relay etc.

Cheers
Chris

Datatek · Nov 24, 2018

Walshie1987 said:
Sorry, so no load when switch off on any wires.

When unplugged 13.5v on the double connector positive, nothing on the single wire.

When plugged in, and switched on, 13.5v on the single wire, 0v on the double connector.

I think they are all driven off 1 relay in the l322?

Will try the basics like relay etc.

Cheers
Chris

Usually 2 relays, one for each side. the single wire you keep referring should should I think be the earth?

Walshie1987 · Nov 24, 2018

Yeah maybe, deceiving though as it's brown ....stupid comment, just realised it's a car so brown doesn't equal live

too used to house electrics

Walshie1987 · Nov 24, 2018

Sorry mate last question, where are the relays, ive been checking the rear panel for some reason. Are they in the front box?

Datatek · Nov 24, 2018

Walshie1987 said:
Sorry mate last question, where are the relays, ive been checking the rear panel for some reason. Are they in the front box?

I suggest you look in the owners handbook, I can't know where every relay on every RR is located

Walshie1987 · Nov 24, 2018

Datatek said:
I suggest you look in the owners handbook, I can't know where every relay on every RR is located

Haha no prob mate. You've been more than helpful. I will crack this later and post how on here.

Cheers
Chris

Datatek · Nov 24, 2018

Walshie1987 said:
Yeah maybe, deceiving though as it's brown ....stupid comment, just realised it's a car so brown doesn't equal live too used to house electrics

If you are a sparks, don't come to France, any colour apart from blue or green/yellow is live in domestic or industrial wiring

Mark Piercy · Nov 25, 2018

Datatek said:
If you are a sparks, don't come to France, any colour apart from blue or green/yellow is live in domestic or industrial wiring

And the live and negative can switch! Hence the double sided RCD.. get your own earth!!

Datatek · Nov 25, 2018

Mark Piercy said:
And the live and negative can switch! Hence the double sided RCD.. get your own earth!!

Not so, it's historical. The supply in France used to be 2 phases out of 3 for domestic use giving 220 volts across the 2 phases, so both conductors were live. When the system was modernised it became 220 and later 240 volts per phase and the neutral was introduced, however double pole switches and isolators were retained and when MCBs were introduced the regs required that they were also double pole. Many French Sparkies still ignore the regs and you may find the neutral on either side of a socket

L322 Heated Windscreen issue - Only Passenger side works

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