II don't have a circuit of he MK1 or Mk2 and cant remember if the screen is split into 2 elements. If it is a single element it could be the screen itself. You need to get a meter on the screen connections.

As I say I don't have a circuit but on the MK3 the ON indication LED comes from the output of the relay which tell you that the relay has pulled in and there should be voltage on the screen fuse(s). I would think that the MK2 has the same configuration.

If the element is a split screen there will be a further ultimate fuse too which protects the wiring and relay. You refer to 'fuses' so I'm now guessing it is a split element and unlikely that both elements would go at once if at all. Though, is the ON indicator is wired as per my second paragraph, the fuse must be OK as the indicator woldnt come on.

Anyone any circuit?

Oh I wish I'd saved my Haynes..

Phil

 

I have read the wiki fuse section and checked fuses 5 and 6 and they are fine,the wiki says there is a relay in the engine compartment but this is the switch timer and i take it that is fine because it does switch itself off,there is another relay but it controls both front and rear but the rear works fine so i don't think its that, i really am stuck what to check next,i do not have a multi-meter so i cannot check the terminals at each end of the windscreen.

 

I hate to state the obvious, but you have checked to make sure you actually HAVE a heated screen??? Obviously the car DID have one as you have the switch, but the last MK2 I had must have had the original heated screen replaced with standard glass before I bought it, hence I had the switch (which even lit up) but no heating elements in the glass.

The screen IS split into two elements, with connectors on the bottom corners. I'm not sure how the circuits are wired though and whether there is one relay or two.

 

Well obviously working on the idea you do have a heated screen.

As I say, if Ford have used the convention that the ON LED is illuminated when the relay has pulled in, then its obviously not the relay (this needs confirming on a circuit/wiring diagram). In the unlikely event of both halves of the screen failing together, what is common.

I cant see both connection to the two fuses coming away together as these will be hard wired into the fuse holder. Again without a wiring diagram, are the 2 screens using a common earth point and has this come adrift. (Mk3 diagram shows where this common earth connection is so I guess a MK2 would too)

I suspect the other relay you refer to that supplies the rear and front heated windows is in the 'smart charge' circuit which prevents you turning on the heater without the engine running and the alternator delivering charge.

Circuit anyone.......

 

ok, a few wiring diagrams for you. though I would suggest, if both sides arer not working, then it will either be a wiring issue on the positive side between the relay and the screens, or an earth issue, as they both share a common earth, the earth is G1, down near the battery I think.

 

ok, bear with me.

low power side of relay, switch turns on relay, and I think sends a signal to alternator to increase power output? or up engine revs or something.
high power side, direct link from battery to relay, through relay, then splits to Fuses 5 and 6, then direct to screen connectors, also lights led on screen switch, so if the LED is working, it has power to the RHS of the heated screen. (at the connection point in the engine fuse box).

both sides then go to earth at G1 (engine compartment, front, LHS), but go through a ground distribution block, located in the centre of the engine bulkhead.

just to be sure, you are checking the fuses in the engine bay, not in the cabin?

hope this helps

 

Yep, you've said it all there. LED says relay is pulled in and that power is to the right hand side fuse so the problem is after than and outsode the junction box (according to the diagram)

Engine revs increase via ECU monitoring the charge voltage out of the alternator, and in an attempt to maintain charge increases idle speed.

Whats that connector, M111/C848

Phil

 

yes i have checked the correct fuses in the engine bay (my names not scooty

) also the revs are going up slightly when i turn heated screens on.It is a heated sreen,i can see the thin wires in the glass.

 

When you say heated screens does that mean engine revs increase when just switching front screens only on too?

 

the revs increase when i turn the front heated screen on

 

Thats as it should be then....

at this stage its probably worth checking the connectors to the screen itself. They shouldn't come undone, but *might* have been left disconnected (by mistake) if the screen has been replaced in the past...? the connectors are under the scuttle panels where the wipers are. I doubt its this, but its worth ruling out. If you've got a meter available, you can check for a current at the connector while your at it!

 

I can see me paying £60 excess for a stonechip thats going to crack my windscreen

 

Really, then that would suggest that the screen is drawing current if the charging circuit works as the original smart charge is supposed to, i.e. when voltage drops due to load then revs increase.

Unless yours senses the relay has pulled in which isn't how the smart charge was supposed to operate.

This is where one of these as a Christmas Present to yourself would be handy. Christmas Present

 

Phil - do you know for certain if its EVER worked?? and is it an original screen (will have a ford logo on it) or a replacement??

 

This is the first week we have had frost so i don't really know,only had the car since august.just going to run out and check if its original screen

 

I will try just the front screen heater tomorrow,i just had a thought would it be slower if i use front and rear together ,so i hope its frosty tonight so i can try it

 

I'll put £1.59 on it being a knackered screen! It'll be knocking on 12-13 years old if it hasn't been changed before.

 

If you want to test it without ice steam the window up and switch it on.

 

The screens should not fail, they dont wear out, and particularly not both sides. You can damage them yes.

Phil even without waiting for frost, just start the car with the interior light on, switch the screen on and you should see a momentary dip in the interior light if the screen is drawing current.

 

Its not the original screen. 4titx i'll try what you suggest now,and also look under scuttle panel to make sure the things wired up.

 

ok,checked under the scuttle,and they are connected,steamed up window switched front screen on,revs raised a little but did'nt clear screen,so i think windows knackered.also spotted another job to do,pollen filter,i don't think its ever been changed.Thanks for all of your help guys

 

my screen takes a fair few minutes (about 5?) to have any effect in the mornings, then only 3/4 of it works!

and if you dont have a tester, solder 2 leads to a lightbulb and check it that way!

or use one of the R5? bulbs (footwell lights) bend the 2 wires downwards and try to get it to connect to the 2 wires on the plug giving power to the screen?

 

Phil I've git rid of my mk2 For a mk3 and still have the haynes manual, if you don't have one? You can have it for the price of postage.

 

Just strange both going at once and its usually only partial as donteus points out.

The increase in engine speed is a sign that extra load has been placed on the electrical system/engine so something is drawing current and the smart charge has operated to maintain charging voltage. Did the interior light dip momentarily?

 

yep,maybe its just really slow.my last car was really quick

 

It should be quick. Mine has never worked since I had the car, but sometimes when I switch it on (it also triggers the heated jets AFAIK) you can just see faint lines appearing as though it is doing something, albeit almost nothing.

All the fuses and relays are fine (the relay clicks on and off with the timer circuit as it should) so I checked the connections under the scuttle panels. I get full voltage across the car side of the connectors but cannot get a continituity reading on the actual element on either side. I've come to the conclusion that it must be the upper connections that are fubared which are impossible to get to without a new screen, everyday now I just hope my screen cracks so I can get a new one on the insurance instead of forking out £450.

 

Just reading your post again, when you say you get full voltage on the car side of get connectors, do you mean the connectors that connect to the screen connectors?

Just seems strange that both are not working.

If your screen works only partially, you would still get almost a short circuit continuity reading across the elements.

Unfortunately I've not seen the connectors in real life as I never had any issues with my MK3 heated screen.

 

The heated jets are powered all he time the ignition is on summer or winter and independent of the heated screens etc.

If it is partly working then you have a poor connection somewhere, something else is getting warm perhaps somewhere too if that the case.

If both sides are not working or partially working, that actually narrows down the wherabouts of the problem.

Tell us about it!!