P38A Heated windscreen, only half working

MY2000 Vogue. New to me, and just looking for advice on a couple of minor issues.

I tried the heated screen out today as the car was properly frosted up this morning. Half the screen cleared really well, the other half not at all. Are there two separate elements in the screen, which might have separate fuses, or is it a fault in the screen itself? Luckily it is the driver's side that clears. It's clear from a couple of inches inside the RH A-pillar to a line just to the right of the mirror - from there to the left edge is not heating. Any thoughts?

Each side has seperate elements, and each has its own fuse but both powered through one relay from what I remember

Thank you! That's what I was hoping to hear Any idea where the fuses are located? I don't have a wiring diagram or manual of any kind.

Cheers.

BlackDogZulu said:

Thank you! That's what I was hoping to hear Any idea where the fuses are located? I don't have a wiring diagram or manual of any kind.
Cheers.

Click to expand...

CIRCUIT OPERATION
This operates only with the engine running, which is
determined by the HEVAC panel. In the off state, the
signal is at 12 volts. When the Heated Front
Windscreen is activated, the signal is switched to 0
volts. This provides the ground required for relay 5 to
be pulled in, as there is an ignition feed on the other
side of the coil provided by relay 15. This relay
energises one half of the heated screen elements.
Once relay 5 has been energised, a 12 volt signal is
provided to the coil of relay 4. The other side of the
coil is connected directly to ground, thereby
energising the relay and switching on the other half
of the elements.
There is also a feed spliced from the harness which
provides the petrol Engine Control Module with a
signal that tells the unit there will be a large electrical
load turned on/off.

BlackDogZulu said:

Thank you! That's what I was hoping to hear Any idea where the fuses are located? I don't have a wiring diagram or manual of any kind.

Cheers.

Click to expand...

I,ve just looked for my P38 manual on disc but cant find it ..........from what I remember the fuses and relay are in the under bonnet fuse box.........but it was several years ago

Outstanding. Thanks guys. Will have a look as soon as I get a minute.

Thanks to Wazzajnr here is all the manuals for you to down load.
https://www.landyzone.co.uk/land-ro...lus-other-useful-info-on-range-rovers.322195/

Brilliant, thank you.

Have now checked the wiring diagrams. My understanding is that the two halves of the screen have two separate supplies, both fused at 30A and with separate relays. The HWS switch energises one relay, which then energises the other. I have tried swapping the relays over, and also the fuses in case of an invisible break, but the results are the same - the left side of the screen won’t clear. From this I am assuming that the fault is either in the wiring to the screen from the relays, or a fault in the screen itself. I’ll do a bit of hunting round with a multimeter, but my guess is that the screen is the problem. There is, of course, a fairly cheap way to solve this with a hammer and a call to Autoglass, but previous experience says this is a Bad Idea. I had a Mondeo and badly chipped the windscreen. I got it repaired on insurance (all above board) but it looked a horrible mess afterwards with black glue everywhere, and most of the heating elements didn’t work. Of course, I had the repair done in spring and didn’t find out the HWS didn’t work until the first frosty day, by which time it was too late to call them back. If it’s the screen at fault, I’ll live with it.

Check for open circuit or heater resistance at C0574 (where it plugs in underneath fuse box) pin 3 and ground. That will get you closer to tying down the problem to fuse box or the screen element itself. There is one more connector to the element under the LH plenum cover and a common ground point for both sides of the screen in the centre under the plenum cover.
I had an intermittent problem with both sides of the screen taking it in turns to work. It turned out to be bad/ corroded connections where the relays plug into the fuse box. Bit of cleaning and a couple of new relays solved the problem.

Should that be ‘high resistance’?

Thanks for this. Will have a look when it warms up later today. Too cold outside for anything other than checking the heated seats

Relay terminals are like new.

BlackDogZulu said:

Should that be ‘high resistance’?

Click to expand...

No. I meant the higher resistance that would be the equivalent of the heater element resistance. Can't remember what that resistance is off-hand. It'll be low though!

Right, thanks. I thought it might be an autocorrect issue! I’ll get the multimeter out there later.