rear window heater

[marc69]

The rear window heater is not working in my SR. I have checked the fuse, the connections on the window and changed the relay and the switch. It won't be the window lines broken as the car is pretty pampered, besides the relay doesn't click and the voltmeter doesn't go down which it should if the circuit is working?

Aside from a broken wire is there anything else easy that it could be?

[marc69]

I had another check of all the fuses etc today and can't find the cause, any clues please?

It's the only fault the SR has now so desperate to get it back to 100%

[marc69]

I have sepnt some time with this,

the fuse is getting current,
the relay works (tested in another Nova)
the switch does work
No current is reaching the back window connections
I spent time checking what currents are reaching the relay (at the bottom of the picture), all but the red wire have nothing, whether the ignition and switch are on or not.
Red..constant 12v
two Blue and white wires..nothing
Black...nothing
Brown/white...nothing
Here's the wires if anyone knows whoch one should do what or what each one is connected to that would be a great help

http://i988.photobucket.com/albums/af5/69marc/Photo639_zps867fccce.jpg

[Benn]

Do any of the lines work?
What about the connection to the glass?

[Jack]

It should be a simple relay. According to Haynes:

Red = +12v (fuse 8, 20A)
Black = feed to window
Brown/White = feed from blower switch
Black/White = feed from charge relay

I'd check the black/white wire out at the alternator, see if thats Ok and is supplying current (no other electrical faults, charge warning light works as normal?). To override the heater/blower switch, earth out the brown/white wire.


[edit] No mention of blue/white wires on the diagrams though, are you sure you got the right relay there?

[marc69]

It should be a simple relay. According to Haynes:

Red = +12v (fuse 8, 20A)
Black = feed to window
Brown/White = feed from blower switch
Black/White = feed from charge relay

I'd check the black/white wire out at the alternator, see if thats Ok and is supplying current (no other electrical faults, charge warning light works as normal?). To override the heater/blower switch, earth out the brown/white wire.


[edit] No mention of blue/white wires on the diagrams though, are you sure you got the right relay there?


Thanks for that, there isn't a black/white wire at the relay but two blue white ones in the one connection?
I assume it's the correct relay because I tested it in the xe which works, with no relay in no rear demister but with the relay in it works fine.


I'll check the wire form the altenator but there are no other electrical problems at all, no warning light and the voltmeter runs fine.

From what you have written there and from what I tested before, there was nothing from the black wire (feeder to the rear window) and there is current at the red wire so, it must be either the blue/white ones (whatever they are) or the brown/white, feed from blower switch, could be this wire is broken.....hopefully

When you say the black/white (blue/white in this car?) wire is the feed from the charge relay, where does this connect too/from?

[marc69]

I have been back out (in the lovely weather) and found that shorting the H+ and rear connections at the switch on the xe operates the realy for the rear window heater.

Doing the same on the SR does nothing, the H+ on it is two brown wires, again I'm confused...

I checked the altenator, the black/white wire is connected firmly and seems to be ok

[marc69]

Been trying to figure this out from the wiring diagram in Hynes for a 1989 model, I have found the bit for the blue/white wire which leaves the relay, it goes from the relay to a small box shape in the diagram with number 117 and there is a 61 immediately below it. I cannot figure out from key what this is? Does anyone know?

[jimbob-mcgrew]

you say your not getting power to the screen ?

are you getting juice out the back of the switch when you switch it on ?

I was gonna say, if you are, the break is probably somewhere in the wire going to the screen. It runs to the passenger side, and along the sill under the plastic trims. I think it earths at the rear of the car, 10mm nut from what I can remember, behind the carpet at the very centre of the back of the car.

if the earth was anything to do with it, youd probably have issues with tail lights etc, so im thinking its either that wire or somehow the screens dead.

you could try manually feeding juice to the screen to see if it works ok.

and you could try manually feeding juice from the back of the switch to the window to check if theres a break in the wire

[marc69]

Thanks, I spent a few hours today on it after trying to make sense of the wiring diagram, basically removing the altenator blue white wire gets it all working, except the ignition light in the dash...wierd any, this lets me know that the switch, wiring to the light and the live feed all work so,

I think it is something to do with the two blue/white wires. The problem is according to haynes ther is only one which then goes to the instrument cluster (there is a blue/white wire here) unless there are two wires, one from the altenator and them the other goes from the relay to the instrument cluster?


Anyway I am now stuck, it works with the blue/white removed from the altenator but does not when it is reattached? Any clues?

[jimbob-mcgrew]

this sounds a bit more complex than my brain can comprehend, im useless with wiring diagrams.

the rear screens not linked to the alternator wiring is it ?

I thought all the alternator side of the loom ran its circuit before it gets to the ignition switch and fusebox ?

im wrong quite a lot tho, so not 100% sure, lol

[jimbob-mcgrew]

is this on your 1.3 carb ?

[marc69]

is this on your 1.3 carb ?Yes it's on the 1.3 SR, from what I can tell from what has been said and the wiring diagram, using the relay as the base,

The red wire is a constant feed which works, (fuse box)
Brown/white wire is from the switch which also works,
Black wire goes to the rear window and it works,
The Blue/white wire is supposed to be attached to the blue/white altenator wire which also goes to the ignition light on the instrument panel,

This is live in my xe when the ignition is switched on but is not on this car.
When I undo the blue/white wire at the altenator it works or, when I short a 12v feed to this blue/white wire at the relay connection it also works but in both cases the ignition light then doesn't work. I have tried putting a wire from the relay to the instrument cluster incase that wire is broken but, it is exactly the same, the one at the altenator is obviously not broken as removal of it makes a difference.

I can only figure out two other theories...the car was fitted with a WASO alarm when new that has two immobilisers (one for the starter and one for the ignition) motion sensors and so on.... there is a lot of additional wiring behind the fusebox, perhaps this has interfered with the rear window wiring?

The black box on the altenator, what does that do? would it stop this from working?

I cannot recall whether the rear window ever worked as this is the first year the car has been an everyday car since I bought it.

[marc69]

It should be a simple relay. According to Haynes:

Red = +12v (fuse 8, 20A)
Black = feed to window
Brown/White = feed from blower switch
Black/White = feed from charge relay

I'd check the black/white wire out at the alternator, see if thats Ok and is supplying current (no other electrical faults, charge warning light works as normal?). To override the heater/blower switch, earth out the brown/white wire.


[edit] No mention of blue/white wires on the diagrams though, are you sure you got the right relay there?

What is the charge relay? I wonder if that's the problem?

[meritlover]

isnt that wire there so that the window heater only comes on when the engine is running/battery charging? its quite a high load. I'd have to check the diagram.

[marc69]

isnt that wire there so that the window heater only comes on when the engine is running/battery charging? its quite a high load. I'd have to check the diagram.

In my other Novas the window heater comes on when the ignition is switched on, you can see the load as the voltmeter drops, and hear the relay click. But evven with the engine running it doesn't work unless the blue/white wire is disconnected from the altenator

[marc69]

GOT IT WORKING!!!!

I cleaned all the altenator connections, ingition connections at the key and changed all the relays, I can now hear the relay clicking on and off and did the test with wire and a bulb from the connections at the back window.

I susopect one of the other relays must have had a fault and been interfreing with it, but that's a guess.

Thanks everyone for help andd advice.

[jimbob-mcgrew]

gwaaan marc :thumb: