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Author Topic: Rear Screen  (Read 25417 times)
davidewanprice
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« 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
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Anders Dinsen
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« Reply #1 on: March 09, 2007, 08:49:40 am »

Hi David and welcome to the forum! and congratulations on your car! Cool

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 Smiley

Cheers,
Anders
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1982 Talbot Matra Murena 2.2 prep 142
2017 BMW i3 "Charged Professional" 94Ah

Used to own:
2001 Renault Matra Grand Espace "The Race" V6 24v
1997 Renault Matra Espace 2.0 8V
1987 Renault Matra Espace J11 2.2
davidewanprice
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« Reply #2 on: March 09, 2007, 07:09:43 pm »

Thanks for the quick advice, will try that. Many thanks
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krede
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« Reply #3 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?
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Lennart Sorth
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« Reply #4 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
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Lennart.Sorth@matrasport.dk
Murena 1983 1.9i silver // Honda e '20 Charge Yellow  // VW Polo '22 1.0 tsi silver//
davidewanprice
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« Reply #5 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.......
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Lennart Sorth
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« Reply #6 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
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Lennart.Sorth@matrasport.dk
Murena 1983 1.9i silver // Honda e '20 Charge Yellow  // VW Polo '22 1.0 tsi silver//
macaroni
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« Reply #7 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.
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zac
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« Reply #8 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...
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Anders Dinsen
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« Reply #9 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... Grin
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1982 Talbot Matra Murena 2.2 prep 142
2017 BMW i3 "Charged Professional" 94Ah

Used to own:
2001 Renault Matra Grand Espace "The Race" V6 24v
1997 Renault Matra Espace 2.0 8V
1987 Renault Matra Espace J11 2.2
krede
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« Reply #10 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  Wink
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davidewanprice
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« Reply #11 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.
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davidewanprice
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« Reply #12 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?
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roy4matra
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« Reply #13 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
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Anders Dinsen
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« Reply #14 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???



- Anders Cool
« Last Edit: October 14, 2007, 01:50:18 pm by Anders Dinsen » Logged

1982 Talbot Matra Murena 2.2 prep 142
2017 BMW i3 "Charged Professional" 94Ah

Used to own:
2001 Renault Matra Grand Espace "The Race" V6 24v
1997 Renault Matra Espace 2.0 8V
1987 Renault Matra Espace J11 2.2
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