GTV Rear screen demister fix.

[stoyce]

Originally Posted by monkeybrain1234

24/0.2 Wire 10m Black, guy in maplins said this was equvialnt to 2.5mm! Is this true? - I have used this wire for the earth connection and the live from the battery. When I tested the system eveything works but the live from the battery seems to get warm. Is this wire thick enough or should I get a thicker one?

Thanks

The guy at Maplins gave you 2.5mm CSA (cross sectional area), not Dia.
You need 2.5mm Dia wire, which is AWG 10 or AWG 12 and rated for 40A.

More info here;

AWG to Square mm Wire Size Converter - Storage

I'll edit my post to read 2.5 Dia, which is 4mm CSA.

The 1mm wire you have is fine for the earth connection, as it just switches the coil on the relay, but you must use the higher rated wire for the power feed.

[monkeybrain1234]

Cheers For info guys, obviously I need to upgrade the wire I have used, but I have been to Maplins and they dont seem to have a wire thick enough, halfords also didn't although they had a live wire for incar audio that could handle 42 Amps.

Not trying to be a useless prat here but Stoyce could you by any chance tell me which wire (part no) to get and where from? I would really appreciate that......

[faceplant]

good fix guide! my old GTV melted the fuse and the 4 around it when the timer failed.

[stoyce]

Originally Posted by monkeybrain1234

could you by any chance tell me which wire (part no) to get and where from? I would really appreciate that......

Maplins should have XR59P, which should do the trick, it will take more than 30A.

Also, VWP - standard cable Ref 65 will do.

[monkeybrain1234]

I have a spare AWG 8 lead that I could use - Would this work?

Says following on wire -CSA TYPE TEW 105°C 600V FT-1 LL55192 E28423 8AWG AWM STYLE 1028 105 C 600V VW-1 BS6231 10MMsq HEAT RESISTANT 90

Is this too thick? Any drawbacks to it being too thick? etc

[stoyce]

Way too thick!!

It will work a treat, the bigger the wire the better its current handling capacity, but it'll be really hard to connect up to the relay and is far too much overkill.

Just find some wire that's as close to the size of the heater wire as possible.

[hlambourn]

sorry this is another issue but i noticed my spade connector has come away from the element on the glass. is there a way to reattach this?

[stoyce]

If the spade terminal is still connected to the element, then you should be able to get some clrear resin / glue to fix it back to the screen. I think Halfords sell something that'll do it, otherwise give someone like Autoglass a call.

If it's broken off from the element, then I don't think theres a fix...

[Stixy]

Originally Posted by hlambourn

sorry this is another issue but i noticed my spade connector has come away from the element on the glass. is there a way to reattach this?

I had the exact same problem, the garaage had to replace rear screen although the tried to reattach the terminal to glass, but every time they laid the glass back down into the car, the terminal broke off!!

[ChrisH]

Great post, I’ve been thinking about doing this for a while and your guide gave me the motivation to get on with it so thanks for that!

Just one little build...

The original rear screen heater circuit also – if fitted – controls the heater wing mirrors so that they defrost as well. This means that even when this upgrade is done, the original circuit will still carry a current load as it will continue to supply the heated mirrors. I would guess these draw far less than the rear screen so it’s not a big deal, but it does mean a 5 amp fuse may not last too long (I’m not sure how much they actually draw). Obviously it is best that the fuse goes before anything else so no need to panic for anyone who has done this, but if you find it blows quickly or repeatedly, this could be why. If so, check your wiring first, but then perhaps try a 10amp fuse which I would guess would cover it.

As for my efforts...

I first had to work out where the fault was in my circuit as it had fried itself some time ago. The connector behind the glove box proved to be OK so the fuse box came under close inspection. The fuse had melted pretty badly and there were signs of damage to the casing itself.

Many hours of testing later showed that the fuse circuit was still working, supplying a fused supply to the relay (which in itself took a while to identify – ever heard of labelling Alfa? Especially when the box you fit looks nothing like the one in the manual!).I also managed to prove that the switched earth from the heater on off switch was working – great as I didn’t want to go messing around with that. The failed point was that the switched supply from the relay which wasn’t getting to the brown and white cable for the main circuit – it had obviously melted somewhere!

Reluctant to part with the best part of £100 for a new fuse box, and even keener to fix it on the Sunday when I couldn’t have got one regardless, I rigged up a little bypass circuit as you can see below. This just allows me to mount the relay remotely and therefore run the switched output directly to the brown and white cable. You can see the spade plugs entering the fuse box in place of the relay, which can be seen tucked away to the right (the bright yellow box). The rest of the fusing and switching works as usual. Bit of a ‘phaf’ but it’s a fairly need job and works a treat so I’m pleased with it, saved me £100 too!

Again, good guide mate, proof that in some cases a few simple tweaks can iron out some of the factory niggles...

Chris

[stoyce]

The mirrors are on the same circuit, but the size of the heater elements are negligable, compared with the rear screen. You'd be lucky if GTV mirrors were rated at 30W. Most will be in the region of 20 to 35W, depending on size/ area of element, so if they are 30W then that equates to 2.5A each, total of 5A.

(Good point on the fuse, if it blows the 5A, stick a 7.5A in there. (Mine is working fine with a 5A in there))...

As for the wire running through the car, there will be no load on it. The wire is only current loaded when powering a large resistance. All you're powering is the relay coil. The mirrors are connected somewhere up front

[ChrisH]

Originally Posted by stoyce

As for the wire running through the car, there will be no load on it. The wire is only current loaded when powering a large resistance. All you're powering is the relay coil. The mirrors are connected somewhere up front

Agree with that, defitnitely a hands down improvement... quite amazing the original design didn't cause a fire or two, Alfa were probably lucky to avoid a recall!

[itacarboy]

just to add to this post.
i may have found a solution to the metal prongs that are attatched with solder to the element
you will have to remove parcel shelf
then use wire wool, brillo pad and clean up an area (take not how they are on there originally)
use spirits, brake cleaner, contact cleaner to clean are that you have keyed
the metal prong if it has entirely come of, cut the prong down so its just the soild peice, not the 2 peices that are originally attached.
clean strap same as the element.
you will then need a big tipped soldering iron. add solder to the prong, with a pair of pliers on other end
get the strap with the solder on very hot, push to screen then hold with pliers until attatched.
clean over solder and element area agian.
then i used some all purpose arildite for glass metal ect, and spread that all over were i could,

seems to have done the job

just be extra carefull

[monkeybrain1234]

I have been meaning to write this for ages.

Thanks goes to Stoyce for this article on this rear demister.

I did it almost a month ago and the result is no more burning smell in the cabin when using the rear heater now. Great news.

I have attached a picture of how my fuse looked under the footwell!! There was no yellow plastic cover of the fuse left, only the two prongs and the fuse element itself as that had not blown. When I saw this I was very glad I did this upgrade.

Fully recommend everyone doing this if needed, Thanks again Stoyce.

[jus]

Originally Posted by stoyce

....The timer on the relay can fail and cause the heater to stay on. ...

will it stay on even with the igntion turned off?

[stoyce]

Originally Posted by jus

will it stay on even with the igntion turned off?

No. It's only powered only when the ignition is on and the switch is operated.

The heater is on a switch, so can be turned off at any time. The timer keeps the heat on for 20 mins first off, then 10 mins (or 5), each time its opperated after that.

[stoyce]

Originally Posted by monkeybrain1234

I have been meaning to write this for ages.

Thanks goes to Stoyce for this article on this rear demister.

I did it almost a month ago and the result is no more burning smell in the cabin when using the rear heater now. Great news.

I have attached a picture of how my fuse looked under the footwell!! There was no yellow plastic cover of the fuse left, only the two prongs and the fuse element itself as that had not blown. When I saw this I was very glad I did this upgrade.

Fully recommend everyone doing this if needed, Thanks again Stoyce.

Excellent news, and well done

I bet it didn't take too long to carry out either?

[jus]

Originally Posted by stoyce

No. It's only powered only when the ignition is on and the switch is operated.

The heater is on a switch, so can be turned off at any time. The timer keeps the heat on for 20 mins first off, then 10 mins (or 5), each time its opperated after that.

ahh I see what you mean. I'm in the midst of investifating a battery drain issue ...

[colma]

Originally Posted by monkeybrain1234

I have been meaning to write this for ages.

Thanks goes to Stoyce for this article on this rear demister.

I did it almost a month ago and the result is no more burning smell in the cabin when using the rear heater now. Great news.

I have attached a picture of how my fuse looked under the footwell!! There was no yellow plastic cover of the fuse left, only the two prongs and the fuse element itself as that had not blown. When I saw this I was very glad I did this upgrade.

Fully recommend everyone doing this if needed, Thanks again Stoyce.

I got that burning smell last week and discovered a very similar senario to your picture today.
I removed the remaining prongs but couldn't put a new fuse in as melting has deformed it.
Is it ok to go without for the moment as I don't really want to spend any more on my car right now?

[stoyce]

Originally Posted by colma

I removed the remaining prongs but couldn't put a new fuse in as melting has deformed it.
Is it ok to go without for the moment as I don't really want to spend any more on my car right now?

Colma
I think its time for a new fuse board... you may be able to find a good second hand one, say from Autoluso or another breaker, (ebay).

It's fine to remove the fuse and not use the rear screen heater. No problems with that.

[colma]

cheers for that.
will go without for a while anyway and get it replaced at next service.
glad that i finally discovered what the smell was :-)

[GCPV6]

[QUOTE=stoyce;3034215]GTV rear screen demister repair:
The problem with the early GTV’s rear screen demister is down to poor basic electrical design.

Hi, Would you call a 2001 GTV and "early" one in this respect, in other words, is mine likely to have this problem? The demister packed up this weekend. The light in the dashboard switch remained on but the screen did not clear at all!

Thanks

[SimonT]

[QUOTE=GCPV6;3190718]

Originally Posted by stoyce

GTV rear screen demister repair:
The problem with the early GTV’s rear screen demister is down to poor basic electrical design.

Hi, Would you call a 2001 GTV and "early" one in this respect, in other words, is mine likely to have this problem? The demister packed up this weekend. The light in the dashboard switch remained on but the screen did not clear at all!

Thanks

Mines 2001 and had the same problem, so seems like the answer is yes. Fixed previously by dealer (think they put in new wiring - said 164s used to be similarly afflicted) which was fine for 2-3years but noticed a smell recently and now have the melting fuse issue. Think I've caught it in time to save the fusebox - will do this fix asap.

[GCPV6]

Many thanks. First things first - I'm going to check my fusebox tonight!

[jus]

How long should the rear demister stay on for before it cuts off?