Unplugged everywhere...

Unfortunately I'm not getting very far with this :(

DaveRover3500s said:
...so check if voltage on that at the heater wire connector in engine bay.....do your wipers work ok?

Dave
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Johnny The Fox said:
Was showing a voltage at the Brown/Green wire at the three way connector adjacent to the steering box /bulkhead.
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I have checked for voltage on the brown/green wire at the connector here & there's nothing..

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So this is likely to be the root of my troubles.
But the wipers are working, which presumably suggests that the fuse box & related connections will be OK?
 
Phil Robson said:
Unfortunately I'm not getting very far with this :(





I have checked for voltage on the brown/green wire at the connector here & there's nothing..

View attachment 28665

So this is likely to be the root of my troubles.
But the wipers are working, which presumably suggests that the fuse box & related connections will be OK?
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Hi Phil. Sorry been away.
In my opinion I think that as you have no voltage at the 3 way connector (the feed wire from fuse box being green brown as Johnny the fox says), then as your wipers are ok that proves there is a feed at the point behind the fuse box where the feed splits to the feed side of the 3 circuits (wipers heater motor and heated rear window). However it’s still very much possible you have an open circuit either at the top part of the heater motor fuse, or the bottom output side of the fuse -or as Johnny has found, fuse itself is defective.

Check behind the fuse box fully to see if you see signs of melting or heat damage and check the heater motor fuse holder tongs for looseness. I would bet the open circuit no voltage issue is fuse box side where the brown green wire originates.
What’s tad annoying is it’s not easy to get to as we get older! Low down and looking up! Especially closely inspecting the fuse box when it’s taken off to see the back of it!

Hope helps Phil.

Dave
 
With this hot weather, means the heater blower is on full speed for long periods, I have now fitted a relay to reduce the load through the fuse box for the motor.
 

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Great job John. I did same but came out the heater fuse to relay trigger feed and put relay up near fuse box. The load feed wire then connected to the wire brown green to the motor input. The fuse for heater in original fuse box now has a 2 amp fuse fitted.

No more high loads to weaken my original fuse box!

Dave
 
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The fuse box connections are not simple clips they are wavy plates seperated by plastic and joined electrically by the fuse end. Each side has different wires attached so you need to check for power at both sides and both ends with no fuse in place. If fuse is only contacting one side only those things connected to that side will work. The things on the un connected side wont but it will look like they all should...Thus you have a wiper that works and a heater that doesn't and a fuse with power....
 
Thank you guys.

I have checked that the heater motor works by connecting the feed wire to a spare battery & earthing the return wires in turn. Both speeds work correctly, so I know the motor is working OK.

I have now also been able to look at the fuse box:

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There is no evidence of any melting :) & there is continuity between the top & bottom of the fuse.

I checked for continuity of supply (lack of resistance) between the lower 23-24 fuse terminal & the feed in the engine bay & it was fine. This is presumably between the fuse & this connection on the circuit diagram:

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I then checked the continuity between the slate/brown heater feed wire & the fuse box:

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Again, this is presumably this connection:

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There was no continuity :(

Any ideas gratefully received.....
 
Hi Phil. I am unsure if I am seeing this right- my pdf of heater wiring does not say slate brown wire is heater blower - that’s heated rear screen on mine…. Brown green wire is heater blower feed

Dave
 
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DaveRover3500s said:
Hi Phil. I am unsure if I am seeing this right- my pdf of heater wiring does not say skate brown wire is heater blower - that’s heated rear screen on mine…. Brown green wire is heater blower feed

Dave
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Thanks Dave.

The yellow sleeve on the slate/brown feed is marked “Heater”, so I assume it relates to no. 40 in the diagram I have.
 
I can only tell you what my series 2 wiring says which is what Johnny The Fox also has on his 75 series 2. It may be marked up heater - but according to the attached pdf of P6 series 2 (late) and my car the slate brown is rear heated screen. Green brown is from fuse to heater motor. That said: with ignition on both heated screen, heater motor and windscreen wiper motor should all be live to and out fuse box vis their fuses- heated screen live to its switch on dash, wipers live to its switch and heater live direct to motor via the connector just before the heater box (3 wire connector). Something is amiss with your wiring mate, your diagram like mine says feed to motor is brown green - not slate- brown. So I know it’s frustrating but I still suggest you have something amiss at fuse box - you mention continuity but not voltage- Mr Chips rightly advised that it’s possible to appear to have continuity but once voltage to applied a bad connection high resistance will stop current flow. Your wipers work so that’s a tick. Again to repeat - ignition feed to fuse box splits and feds wipers, heated rear screen and heater blower fuses - I think Mike said how re via fuse bases etc. If you have 12v wire and connect to the + battery you could use to feed heater motor via bottom of heater motor fuse then to top of its fuse see what you get - it will back feed though so if you want and wire is ok for 20smps, put wipers on they should come on to.

Hope this helps.

PS The fact you have wire indents is I think unusual- someone has been in and done that… why?

Dave
 

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I was thinking Phil- you could always check behind the heated rear screen switch on your drivers side dash and checking wiring colour code. The wire from the fuse to it should be slate brown stripe. That would be easy to check from under dash with knee box I open am sure.

Dave
 
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Couple pics of what I have found before Phil - what year wiring diagram are you using might be earlier version than mine from 1975.This loom suffered overheating at fuse box - heater blower and wipers feeds. Note its green brown wire from fuse output.

Dave
 

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Ive found in the past that a connection that wasnt doing its job turned out to be an easy fix by removing the fuses at the fuse holder and doing a bit of a clean up with light emery paper on all the connections and fuse wire ends.
Simple but often overlooked.
 
The slate/ brown wire, might have a sleeve on it saying heater, but it refers to heated rear scorn not heater blower motor, Trace the slate/brown wire, I bet it goes to the heated rear window switch, which on 75 year Series 2 cars is a red illuminated rocker switch, to the right of the steering wheel, above the shin bin.. Exactly as Dave has said, the green/ brown s the live feed from the fuse box to the heater motor.
 
The wiring diagram I'm using is for 'New Look 3500 & Manual 3500S suffix A'. Admittedly the one I use in the garage is a Haynes book, but it is a direct copy of the Factory Manual's diagram:

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:hmm:
 
If yours is a Series 2 with round instruments with suffix letter E at the end of your chassis number late 74 and on this is the wiring diagram for you !
 

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So have had a look at your series A wiring - quite different! Ok so diagram is right Phil - and your diagram also shows that heater motor feed is Brown Green where it connects to the final connector near heater box under front scuttle.

Point 40 brown purple wire is fed via Lucas connector from output of a heated screen and heater motor relay - we don’t have this on series E wired cars!

The relay is triggered by white wire from top of windscreen wiper motor fuse connection to the relay to bring that relay in. - looks like that relay is permanently triggered - energised and is there to take the load of ignition switch I guess. Seems good idea! They took that off series E!

So have you confirmed that relay is ok and you have 12v at the point 40 and heater fuse?

Thanks for your wiring diagram I can see how much they differ from ours!

Dave


Dave
 
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After checking virtually everything heater-blower related, I went out in BOP last night & thought I'd just try the heater fan - it worked fine.... o_O

I think it may have been the prodding around the fusebox terminal that corrected it, which gives me a head-start if it stops working again! I may well do some further crimping & cleaning to be on the safe side.

Thank you for everyone's help.

"I'll be back.." ;) (probably!)
 
One thought, if the fan died after prolonged use. Check the rivet contact on the plastic console housing. I had mine overheat from tarnishing causing resistance. When hot it would sink into the plastic.
 
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