Heated Rear Windscreen Help

[Cruiserdude]

Hi All,

Hope you’re all enjoying a very Merry Christmas time!

Just after a little help please....

Trying to sort out my heated screen and remember reading a few of you have had issues before. I’m not quite ready to give up on it so would be grateful to hear what seem to be the normal problems.

The ‘element’(lines) etc all look to be in great shape, however, my continuity tester suggests otherwise. I have power to one side but not the other. Is this correct or should there be power to both sides? (If it makes any difference, there is a tint applied over the top)

Thanks for any pointers
Best regards,
Mark

 

[Dave2000]

Positive to one side earth the other. Using an ohm meter whilst logical it mean scratching the element coating, this will cause corrosion in the long term. Put your meter connection between the two cables to check voltage.

I may be wrong but IIRC the circuit will activate only when the ignition is on and also 'may' need the engine running?

Not with car ATM and I have not used the HRW for years.

Regards

Dave

 

[Towpack]

Dave is correct in that the ign needs to be on. Neg (earth) on on of the feed wires and pos on the other. Can't remember which one is which. Testing the individual elements with a test meter (ohm meter) is virtually impossible due to the low resistance involved. If they're all bad you'll get open circuit but if it's only 3 or 4 you'll still get a reading from the other good elements. Only way is to steam up the window and switch it on which will show the bad elements if there are any, then mark the breaks in the elements with a china graph pencil or similar if you intend to try a repair with some of the special silver compound paint to restore connectivity. I've tried this and the results were rubbish. Ended up biting the bullit in the end and fitting a new screen.

 

[chapel gate]

You can get after market element kits, i have one boxed in the loft..
Went with a new screen in the end.

 

[Cruiserdude]

Hi Guys,

Much obliged for your replies, that certainly gives me some better info to do some testing. Appreciate your help. Hopefully it won’t end up in a new screen.

Cheers,
Mark

 

[StarCruiser]

TP has it spot on. It's a real faff trying to find the breaks as they're not easily visible and the coating over them means having to scratch through to get a connection tracing on ohms. Complete waste of time IMO. Even if you do fog it up you may have more than one break in each track.
If you really want to try, another way to test it is with power applied, meter set to volts test between earth and move along the track until the meter jumps to 12v, there's break 1, repair and test again.

I had a rear screen shatter once in a Volvo where the glass just crazed with no hole or anything. I didn't even shut it down hard, just came out one morning to find it gone.…

 

[karl webster]

If it ends up a new screen mate I can let you have one for very little at the next club meet we have. Think a new screens around £300 if I remember rightm

 

[Towpack]

I had a new screen fitted by Auto Windscreens for £246 who then invoiced me for a further £211 on completion. Turned out they'd quoted me the wrong price initially so I didn't pay the extra but their service was rubbish. They brought the wrong screen to start with, then missed appointments, the screen leaked after even being removed and refitted twice. Ended up removing and reffitting it myself. I wouldn't recommend them to my worst enemy.

 

[frank rabbets]

I assume the earth wire is not faulty? There is a grommet you can pull out and there is an earth wire connection in there which corrodes. Did on mine anyway.

 

[Cruiserdude]

Thanks to all of you for your info and offers. Think I’ll steer well clear of Auto Windscreens TP, cheers! Thanks Karl, a little more testing to do but an inexpensive replacement might be a great answer. I’m temporarily in Cambridge and normally based 9 hours drive north so anything I can get done over the next week would be a real bonus as I’m rarely this far south at the moment. If you’re not too far maybe I could come and pick it up?

I’ve tried a substitute earth wire FR but seems to make no difference? And the strange thing is, is that the screen looks immaculate!

Head scratching continues!

Thanks again and a Happy New Year to you all
Mark

 

[Dave2000]

Did you get voltage to the opposite end Frank is talking about opposite side to the earth?

Getting 12v does not gaurantee there are amps available but it would be a good start. There is a plug in the IIRC left hand side under the jack? This gets wet, so you may have corrosion in there, enough corrosion to impede the amps but not enough to stop volts.

Regards

Dave

 

[Cruiserdude]

Hi Dave,

Mmm... now you have me thinking, I didn’t realise that could happen. (Electrics aren’t my strong point).

So I measured around 12.5 volts on the one side (left) when the switch was on and yes, that side has had dampness in the past! Would simply drying and cleaning up the connections sort the amps issue? There is also a blue unused socket/plug down under the jack

Going to check the amp reading now....

Cheers,
Mark

 

[Towpack]

The HRW draws around 10-12A and is fused at 20A. If you don't have a
suitable ammeter function on your test meter just use something thats draws a similar current, maybe a 55/60w headlamp bulb with both filaments lit, and connect it up across the 2 feed wires to the HRW element. It should light up at full brightness.

 

[Cruiserdude]

Hi TP/Dave,

That’s a nice simple idea, cheers! I did put my multimeter on it and while I’m still getting to grips with multimeters it appeared to read only 0.5 amps and actually 14volts with engine on. Will try your idea with the bulb tomorrow morning.

Thanks guys,
Mark

 

[StarCruiser]

Hmmm, I think I get what some of these posts are intending but you really don't have amps available (aside from the capacity of the battery that is), amps are drawn by a load and limited by resistance. You couldn't for instance have 12v to 14v at the HRW if intact with it drawing 0.5A. That indicates that much of the element is gone otherwise you would have lower voltage across the heater, indicating there was resistance elsewhere in the circuit. The 55w lamp suggestion is a good one as it will draw a current and from what you've told me it will light brightly. I don't think your connector by the jack is to blame here, I think it's the heater itself and yes it will look perfect.

I'm toying with the idea of fitting 12v fan heaters to demist the rear screen as mine is deceased in at least 3 of the wires.

To test for poor conductivity from battery to heater, test from battery + to heater + on volts with heater on, or better still a known load like a lamp connected across the heater. You should get less than 1 volt. Likewise test between battery - and heater - you should get less than 1 volt. The lower these readings are the better your connections are.

 

[chapel gate]

https://www.frostfighter.com/clear-view-defrosters-about.htm

 

[StarCruiser]

That looks useful CG.
There's an info page that details finding breaks which may be helpful to you CD.

I might order one or at least look into it. Is this the one you've got sitting in your garage CG?

 

[chapel gate]

That looks useful CG.
There's an info page that details finding breaks which may be helpful to you CD.

I might order one or at least look into it. Is this the one you've got sitting in your garage CG?

It is rich. I put it in the loft though cos its nice and dry in there..

 

[Towpack]

I'd love a heated windscreen like some cars have as OEM (and my works Transit) but came up with nothing after making enquiries with various glass replacement companies. They clear the screen in a minute or so. I wonder how much it would cost to have one made for a 80 series? The wiring would be pretty simple to sort.

 

[chapel gate]

I'd love a heated windscreen like some cars have as OEM (and my works Transit) but came up with nothing after making enquiries with various glass replacement companies. They clear the screen in a minute or so. I wonder how much it would cost to have one made for a 80 series? The wiring would be pretty simple to sort.

IM with you on that. Save me at least 10 mins on a winters morning.. and some diesel..