MatraSport Forum

Each model => Murena => Topic started by: davidewanprice on March 09, 2007, 12:17:41 am



Title: Rear Screen
Post by: davidewanprice on March 09, 2007, 12:17:41 am
Hi there im new to the forum and just got myself a Murena and loving it, from now on i'll be posting many stupid questions in the quest of improving my murena. Anyway my first question is about the heated rear sceen, is everyone elses totally in effective, it does work after 20 minutes but only just, can i do anything that will improve it? Thanks


Title: Re: Rear Screen
Post by: Anders Dinsen on March 09, 2007, 08:49:40 am
Hi David and welcome to the forum! and congratulations on your car! 8)

The first thing I think you should check is whether there's wet in the trunk. When the engine heats up, any moisture trapped in the carpet in the bottom with vaporise and make the situation worse back there.

The next thing is whether the wind screen heater is receiving the power it needs. To check that, I suggest you turn on the heater, measure battery voltage at the battery, and then measure voltage across the heater. There shouldn't be that much difference. If there's more than 1V or so of difference, then there's likely to be a problem somewhere in the feed to the heater.

You will notice that it is powered through the struts, so measure at the base of these too. And if that still doesn't show anything, then you need to measure at the power feed to the relay in the engine room. It's located at the fire wall, right side of the engine room.

This relay is known to give problems since the environment is a little harsh down where it sits.

This should get you started :)

Cheers,
Anders


Title: Re: Rear Screen
Post by: davidewanprice on March 09, 2007, 07:09:43 pm
Thanks for the quick advice, will try that. Many thanks


Title: Re: Rear Screen
Post by: krede on March 11, 2007, 04:22:20 pm
My rear window heater WORKS the way it is intented to ( i think) but after a few kelometers in damp weather, the window still "fogs up".. It is as Anders said due to the fact that moisture/water trapped in the trunk is heated by the engine and has no where to escape...
As of now I have no solution to the problem.... apart from trying to seal the rear quater windows the best I can...
perhaps some form of coating on the windows would help?


Title: Re: Rear Screen
Post by: Lennart Sorth on March 11, 2007, 05:59:25 pm
As of now I have no solution to the problem.... apart from trying to seal the rear quater windows the best I can...

Are you sure the water comes from the rear quarter windows ?
The most common leak is the rivets along the underside of the "gutter" under the bottom of the rear hatch itself. 

/Lennart


Title: Re: Rear Screen
Post by: davidewanprice on March 11, 2007, 07:29:32 pm
The inner of the car as a whole is very dry, despite the fact ive no inner covers for the rear lights (of which i will be purchasing asap, i think politecnic do some) also i was given a device that is supposed to soak up excess moisture, seems to work, no i think its down to a loss in voltage somewhere, im going to spend some time over the next few days.......


Title: Re: Rear Screen
Post by: Lennart Sorth on March 11, 2007, 11:31:46 pm
i think its down to a loss in voltage somewhere
Highly likely.
I would start by looking at the connectors at the base of the gas-struts, - the ones near the window itself are rarely bad (unless broken completely).  The voltmeter is your friend. - good luck.  :-)

/Lennart


Title: Re: Rear Screen
Post by: macaroni on March 12, 2007, 12:04:38 am
Hi and welcome.
Mine didn't work at first so I took it to an auto-electrician and they sorted it. It workds very well now, although I tend to leave it on all the time.


Title: Re: Rear Screen
Post by: zac on March 14, 2007, 03:50:47 pm
There is also the low tech approach of leaving the engine cover open slightly (worked for my old 2.2)

I've got all this to come with the new car, still trying to locate all the bits that went missing while the engine was out...


Title: Re: Rear Screen
Post by: Anders Dinsen on March 14, 2007, 04:59:48 pm
I've got all this to come with the new car, still trying to locate all the bits that went missing while the engine was out...

If you were my 8 year old son, I'd check your bed first... ;D


Title: Re: Rear Screen
Post by: krede on March 15, 2007, 05:23:27 pm
Quote
Are you sure the water comes from the rear quarter windows ?
The most common leak is the rivets along the underside of the "gutter" under the bottom of the rear hatch itself.

Yep.. a trip to the carwash made it painfully clear where all the water came from  ;)


Title: Re: Rear Screen
Post by: davidewanprice on March 15, 2007, 08:22:25 pm
Another thing leant, i'll stick to the hand washing then, im supprised i dont get more water leaking in to the boot, my rear light covers have died a death several times over, has anyone bought the politecnic reproductions? i was thinking of making something but if they do the job i may invest.


Title: Re: Rear Screen
Post by: davidewanprice on August 10, 2007, 08:29:50 pm
Ok ive finally used the multimeter (my friend!) on the rear sceen, at the base of the struts it reads 11.8 Volts, touching the metal at on either side of the screen the voltage drops by a volt (meaning some loss but still a working circuit). So if my voltage remains this high why is the effect of my heater so poor? any ideas? Is a loss of 1.2 volts enogh to loose function?


Title: Re: Rear Screen
Post by: roy4matra on August 12, 2007, 05:08:29 pm
Ok ive finally used the multimeter (my friend!) on the rear sceen, at the base of the struts it reads 11.8 Volts, touching the metal at on either side of the screen the voltage drops by a volt (meaning some loss but still a working circuit). So if my voltage remains this high why is the effect of my heater so poor? any ideas? Is a loss of 1.2 volts enogh to loose function?

If you had the multi-meter probes on the screen contact +ve (right side) and a good earth and had 11.8 volts showing, and then on the -ve contact (left side) and the same good earth, and it then showed only 1.2 volts less (i.e. 10.6 volts) then the HRW earth is almost non-existent.  The voltage at the screen contact on the left should be zero.  The heating element should be using all the voltage, and the earth side should be the same as earth!  With only a 1.2 volt drop you cannot expect any heating effect.  Check the earth wiring as it obviously has a high resistance.  It usually starts breaking where it bends continually as you open and close the hatch.  Also clean the actual earth point as the zinc creeps back under these and ruins the contact.

Roy


Title: Re: Rear Screen
Post by: Anders Dinsen on October 14, 2007, 01:48:12 pm
Time to reviewe this thread as I've been looking for reasons to find out why my rear window heater (as everyone elses apparantly) isn't particularly effective. I have found that the power drawn by it is actually quite low, only a few watts, and having been through everything else I'm wondering if the aluminum strips on the rear window are still in good state or if it was really designed to be this weak. Here's a photo of one of them (taken on super-macro!) of one of them. Is this corrosion???

(http://gallery.dinsen.net/d/1428-2/DSCF0319.JPG)

- Anders 8)


Title: Re: Rear Screen
Post by: Anders Dinsen on November 21, 2007, 10:25:03 pm
Anyone here has any experience with this:

http://shop1.actinicexpress.co.uk/shops/Rat_Sport/index.php?cat=Rear_Screen_Demister_Kit (http://shop1.actinicexpress.co.uk/shops/Rat_Sport/index.php?cat=Rear_Screen_Demister_Kit)

(http://shop1.actinicexpress.co.uk/shops/Rat_Sport/images/catalog/rearscreendemisterkit.jpg)


Title: Re: Rear Screen
Post by: Martin Tyas on November 22, 2007, 11:23:59 am
Anders, I fitted a similar kit to a 1964 Hillman Super Minx I had until a few years ago.... thinking back I don't really know what was "Super" about it at all.... probably that it had a few more chrome trims than the standard Minx  ;)

It worked very well until the track started peeling off the glass towards the end of the first winter of use  ::)
I tried a second one that did last and worked for quite a few years... but I fitted that one during the summer. It seems to me that one of the biggest problems is that, quite understandably, people wait until winter to fit them when they start having a problem with condensation and then wonder why, as I did, that they don't stick to the glass indefinitely. In my experience of them they ideally need fitting in summer when condensation doesn't form on the glass as soon as you put your hand near it to start applying the heater track.

Hopefully glue technology will also have improved since then anyway but the best pieces of advice I could give are
1) make sure that the glass is perfectly clean
2) fit them when the glass is warm or at least when condensation cannot easily form
3) be very careful when cleaning the screen once they are fitted because the heater elements being simply bonded to the glass with a thin layer of adhesive don't hold up so well to rough treatment with a window leather.

Oh... and one other thing I am reminded of whilst looking again at the photo of the kit. Instead of rolling up the heater element and it's backing paper when packaging it they instead fold it over. I assume that it will be the same as the one I fitted years ago and like ordinary decals in that you apply the heater track to the window along with the backing paper and then peel off the backing paper once the elements are bonded to the glass. I found with the first one I fitted that the heater element tracks become very slightly stretched at the point of folding so when you come to apply and smooth them out flat then the elements can ripple or pucker in the area where they have been folded. That will have resulted in poor bonding of the tracks in that area and... surprise, surprise... that was where subsequently they started to come adrift from the glass.
So the 4th piece of advice if you do try one of these kits is to take it out of the packaging and either roll it up loosely or lay it out flat and leave for a couple of weeks like that to settle before attempting to fit it.

Martin


Title: Re: Rear Screen
Post by: Anders Dinsen on November 22, 2007, 12:03:11 pm
Thanks a lot, Martin for your practical advice. Nice to see you on the Murena section too! :)

In this case I'll have the existing strips to cater for too, I don't think it's possible to simply remove those, as they are probably not simply glued on the glass, but I was hoping perhaps it would be possible to put the new strips on top of the old ones. The kit looks like it has been designed for cars without any rear screen heating (like your Minx).

So I don't imagine it's going to be an easy fix or upgrade, and I suppose I was hoping that someone had tried this on a Murena or Bagheera - but since nobody answered my first post, I don't think that's likely.

But your advice to wait until summer is certainly very good - I really get the point! I'll go and fit one of those small electric cabin heaters and wire it in parallel with the rear screen, that could also help on the side window, which also mists a good deal. With all the bicycles we have here in Copenhagen, one has to have good visibility out the back!

- Anders 8)


Title: Re: Rear Screen
Post by: lewisman on November 22, 2007, 10:53:23 pm
http://www.speeding.co.uk/acatalog/PermaPoxy_Expoxies___Sealants.html (http://www.speeding.co.uk/acatalog/PermaPoxy_Expoxies___Sealants.html)

This might be worth a try...

I repaired a hrw with a silver based paint many moons ago with some success.


Title: Re: Rear Screen
Post by: Lennart Sorth on November 26, 2007, 01:18:47 am
've been looking for reasons to find out why my rear window heater isn't particularly effective.

I think the rear window heater is lower power than modern cars, but they should be able to demist the rear window in most cases.

However, have you tried feeding it 12V - say straight from the battery ?  - just to make absolutely sure it really is the heater strips themselves (or their connectors) that are poor ?

Also, IF the strips themselves are corroded, I would find it somewhat surprising if they ALL were equally corroded. It would make much more sense if some were more corroded than others, which would show as uneven effectiveness. (?)

/Lennart


Title: Re: Rear Screen
Post by: Anders Dinsen on November 26, 2007, 08:49:56 am
Lewisman, thanks for your link. I have one of those (a Loctite product, though, but seems to be the same content), but I haven't used it as I thought "which strip should I apply it to?" - they are all bad ;)

I've been looking for reasons to find out why my rear window heater isn't particularly effective.

I think the rear window heater is lower power than modern cars, but they should be able to demist the rear window in most cases.

However, have you tried feeding it 12V - say straight from the battery ?  - just to make absolutely sure it really is the heater strips themselves (or their connectors) that are poor ?

No not exactly that, but I've measured the voltage drop from the battery to the screen and it's virtually zero. All components are repaired or replaced :) So I think I have ruled out everything else...

Quote
Also, IF the strips themselves are corroded, I would find it somewhat surprising if they ALL were equally corroded. It would make much more sense if some were more corroded than others, which would show as uneven effectiveness. (?)

Well there are a few hot spots (indicating more corrosion), but nothing serious and no broken strips.

And why shouldn't they have corroded evenly? They are exposed to the same environment, and probably carefully made with the same width and thickness (to avoid hot spots when new).

It *is* aluminum, and a very thin layer of it, and since I think it's only protected by a thin layer of some kind of paint, it makes sense that they reduce in width over time. If only they had used silver... :D

But I agree it's likely that it was probably designed to be less powerful than demisters on modern cars. I just don't think they should be *this* bad ;), and further more, the current drawn by the screen is only a few Ampere, which does not make sense considering the large square wire running from the fuse box, the relay, and the large Amp fuse dedicated to the demister.

So I guess I still stick to the corrosion theory... but I would like to have more than 'circumstantial evidence' :D

- Anders


Title: Re: Rear Screen
Post by: Lennart Sorth on November 29, 2007, 08:16:47 pm
And why shouldn't they have corroded evenly?
for the same reason an unprotected steel plate (read Simca 1100 :-) ) doesn't rust evenly - it always starts at the weakest spot and builds from there.

The Simca 1100 however had a very effective rust accelerator in the way the steel had been folded and flattened several times like a Samurai sword - producing very strong steel with very little material (weight). As soon as rust got hold of the first layer, it spread throughout the entire panel rather quickly. But thats another story :)


Quote
It *is* aluminum
Now I don't normally correct language on the forum, but I know you can take this Anders - all in a good spirit.
its *aluminium*.
Only Americans think its called AlUUUminum ... Jeremy Clarkson makes some excellent jokes on this :-)

And if you can handle this without being insulted, I'll buy you a beer at Christmas.
maybe also even if you do. :)

/Lennart


Title: Re: Rear Screen
Post by: krede on November 29, 2007, 10:17:26 pm
I can handle being insulted!! (Well I have to really.... since im so poor at fighting).... so can I have a beer too? ;D ;D ;D


Title: Re: Rear Screen
Post by: Anders Dinsen on November 29, 2007, 10:41:24 pm
And why shouldn't they have corroded evenly?
for the same reason an unprotected steel plate (read Simca 1100 :-) ) doesn't rust evenly - it always starts at the weakest spot and builds from there.

The Simca 1100 however had a very effective rust accelerator in the way the steel had been folded and flattened several times like a Samurai sword - producing very strong steel with very little material (weight). As soon as rust got hold of the first layer, it spread throughout the entire panel rather quickly. But thats another story :)


Quote
It *is* aluminum
Now I don't normally correct language on the forum, but I know you can take this Anders - all in a good spirit.
its *aluminium*.
Only Americans think its called AlUUUminum ... Jeremy Clarkson makes some excellent jokes on this :-)

And if you can handle this without being insulted, I'll buy you a beer at Christmas.
maybe also even if you do. :)

/Lennart

Come on, you love correcting others don't you :)

Aluminuioum or whatever... Call it Al (there was a song about that...)

You owe me a beer, I just laughed :D


Title: Re: Rear Screen
Post by: Lennart Sorth on November 30, 2007, 02:22:02 pm
Iso can I have a beer too? ;D ;D ;D
Of course! - lets meet up at The Elm Tree in Beech Hill one of these days, ok ?
/Lennart


Title: Re: Rear Screen
Post by: Lennart Sorth on November 30, 2007, 02:24:03 pm
[You owe me a beer, I just laughed :D
Excellent! 
And today I was corrected at work for talking about "the sidewalk" when it is actually called pavement in UK ... so I guess I own myself a beer to ... or something :)

/Lennart


Title: Re: Rear Screen
Post by: krede on November 30, 2007, 02:43:59 pm
He he yep... try to "pop the hood" in England... and what you will actually be ending up doing is "lifting the bonnet"   :D


Title: Re: Rear Screen
Post by: lewisman on December 01, 2007, 02:16:13 am
Only Yanks call them hoods... we call the bonnets too ;)

Mind you poping a hood could well be a mafia term ;D