C

Crunchy

Member
NOW FIXED - THANKS ALL.

Hi guys, always happens at the wrong time - the heater blower fan on my 1998 Disco 300tdi has just packed in. Nothing on any setting, fuses all check out OK.

I need to pick up a load of family and ferry them around a bit this week and need a quick bodge short of pulling out half the dash and centre console - is there anywhere easy I can tap into the circuit to pop a simple switch so it can blow on max fan on/off? Presuming the actual fan unit itself is not the issue?
 
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You will have to tell us whats wrong.
So are u getting a 12v supply at the blower relay ? if so does the relay operate, all thats left is the blower motor and its switch/ speed resistor unit (max speed is the default speed) and of course the ignition load relay and fuses 15 plus fuse 6 in the lower aux fuse panel.

There’s already an existing thread on a heater fan not functioning… somewhere :(
 
Hi guys, still flummoxed by this. Is there a really, really simple way to bodge this albeit safely if I just bypass all the resistors and switches by running a simple switched direct (fused) supply?

All I really need is to have the blower off or just on at max.

If so where do I find + into the blower motor please?
 
Crunchy said:
Hi guys, still flummoxed by this. Is there a really, really simple way to bodge this albeit safely if I just bypass all the resistors and switches by running a simple switched direct (fused) supply?

All I really need is to have the blower off or just on at max.

If so where do I find + into the blower motor please?
Click to expand...
If you are going to bodge it, you'd still be better to do it via a relay. Thick wires to and from the fan as they can take loads of watts.
I'd also be tempted to wire it connected to permanent live with it being switched through the negatve lead. This used to be common practice for high current draw electrical items.
So I'd wire it directly from the battery.
You could use a feed from the "ignition on" lead at the steering column to power the positive side of your switch to the relay, negative from that to any good earth and the thick negative wire from the fan, back to the batt or the earth point nearest it.
But then what do I know?
I'm just a thick, old, old skool guy.;)

So I've now run off to a safe place and put my steel helmet on!:eek:

But this is how I have wired up my electrical cooling fan in my 300tdi since I removed the viscous one. It works just fine. And I expect this/my fan is bigger.;)
 
Crunchy said:
If so where do I find + into the blower motor please?
Click to expand...

on the motor, in the passenger footwell - have a look in RAVE for cable colours and such .... you could get a cheapo speed controller from the zone too - might make things a bit better / easier ...
 
Stanleysteamer said:
I'd also be tempted to wire it connected to permanent live with it being switched through the negatve lead. This used to be common practice for high current draw electrical items.
Click to expand...
Maybe if those circuits are made by butchers .... no offence but who told you that was wrong cos on the contrary, some sensitive electronic circuits/digital signals are controlled by switched earth.
 
Cheers guys, I have had a good rummage about in the footwell before posting and had a look at the wiring diagrams etc but still confused - all I can see going into the motor (both in situ and on the diagrams) are red/white and black/orange but both are earths.

Anyone who has done it can point me to the exact colour of + in and the location please. I've no problem making a safe switched and fused supply - it's just finding the actual + in...
 
Go to the blower relay's plug(C2068) it has a blue/red wire in pin 5, cut it and connect ignition live to it through your additional switch also connect the brown wire at pin 3 to earth, cut the black/orange wire at the motor's plug and conenct that to earth too... then you have controll of the blower on full speed through your switch and the live to the motor is through the original relay and fuse(MF2 60A engine bay fusebox) while your switched live has low current as it's connected to the relay's coil....provided it's not some short circuit somewhere cos on the white/red wire at the motor is not supposed to be earth, that's the live side
 

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sierrafery said:
Maybe if those circuits are made by butchers .... no offence but who told you that was wrong cos on the contrary, some sensitive electronic circuits/digital signals are controlled by switched earth.
Click to expand...
I don't see your argument here. It would appear you actually agree with me. I don't think I actually said is was wrong, cos I never thought it was. With switched earth surely the pressure on the relay in terms of heat etc is less, no?
I have worked on a mate's Series and found even the horn was switched earth, by design.
The only danger I felt there was with this is what happened if the live wire to the unit rubbed on the chassis or something causing a dramatic short to earth.
This was what had happened with his horn and it drained his batt so much he constantly had to start it with the starting handle!
(He'd found a break in the wire, twisted the ends together and "insulated" the join with sellotape!)
I am, as you well know, not used to, or very clever with sensitive electronic signals. One of my kit cars has precisely three fuses. That's it! Based on a Morris Marina.
And the one I am building at the moment based on a Ford Cortina Mk 4, has no complicated modern electronics. But at least it has relays!
You are well aware that I know my shortcomings and that I am always keen to learn.
I always appreciate your comments.:):):)
 
Stanleysteamer said:
I have worked on a mate's Series and found even the horn was switched earth, by design
Click to expand...
The Series have positive earth so the positive was switched not the negative, my disagreement in the other reply was for the quoted part only where you recommended to connect permannent live and switch the earth(negative in this case) which is not OK especially on loaded circuits
 
sierrafery said:
Go to the blower relay's plug(C2068) it has a blue/red wire in pin 5, cut it and connect ignition live to it through your additional switch also connect the brown wire at pin 3 to earth, cut the black/orange wire at the motor's plug and conenct that to earth too... then you have controll of the blower on full speed through your switch and the live to the motor is through the original relay and fuse(MF2 60A engine bay fusebox) while your switched live has low current as it's connected to the relay's coil....provided it's not some short circuit somewhere cos on the white/red wire at the motor is not supposed to be earth, that's the live side
Click to expand...

EDITED.

OK, plug and relay out - five wires, tested with multimeter and checking for reading with ignition on/off and fan slider on/off:

(Regarding the black/orange thick wire to the motor = this is permanent earth).

red/white (thick) no reading = from below this must be the +12v feed to motor.

brown = switched earth (switched with fan slider).

blue/red = ? no reading

white/black = ? no reading

red (thick) - permanent +12v

So to bodge it, I can just bypass the relay and jumper the red 12v feed to the red/white motor feed to give me all 4 fan speeds but this will of course flatten the battery if it is left on and forgotten.

EDIT: above is no good as the fan still runs in speed 1 even if fan slider is 'off'. So, I'd need a switch regardless but guessing a new relay is what I need?

So the 12v in is OK and the fan switch is working on all positions and switching the earth to the relay OK.

Does all this simply mean the relay is fooked? - it does not click.
 
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With ignition on you must get +12V on the blue/red wire which comes from the ignition load relay, if that's missing the problem is on that path, check fuse F6 sattelite fusebox, apply voltage to that pin with a wire and the relay must click and blower start hence my first reply
 
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sierrafery said:
The Series have positive earth so the positive was switched not the negative, my disagreement in the other reply was for the quoted part only where you recommended to connect permannent live and switch the earth(negative in this case) which is not OK especially on loaded circuits
Click to expand...
I have no idea about whether his Series was positive or negative earth, it wasn't an early one, and anyway lots of people changed the polarity of positive earth to negative earth for all sorts of reasons, fitting radios would be one.
Whatever the polarity the feed to his horn was shorting to earth for the reason described and sorting it out was down to a proper connection and decent insulation.
As you know, I have a lot to learn and would be very interested to know what is wrong with switching the (negative) earth on a loaded circuit or any other.
I daresay I picked up on this from some person in my past who appeared to know more than I did.:rolleyes:
 
Right, sierrafery - I cannot thank you enough for the clear instructions and help with this. ;):)

Fuse good and applying 12v to blue/red does indeed allow relay to click and fan work as it should on all settings.

Does the ignition load relay serve anything else as not noticed other failures? And can you tell me the location or if not important can I just borrow another ignition switched 12v supply to serve the blower motor relay?
 
sierrafery said:
The Series have positive earth so the positive was switched not the negative, my disagreement in the other reply was for the quoted part only where you recommended to connect permannent live and switch the earth(negative in this case) which is not OK especially on loaded circuits
Click to expand...
I have since tried to find out more on this as i am very interested.
I found this discussion which has clarified the matter and back EMF seems to be what you were on about.
So for anyone else interested, here is a link.
http://www.locostbuilders.co.uk/viewthread.php?tid=57804
 
Crunchy said:
Right, sierrafery - I cannot thank you enough for the clear instructions and help with this. ;):)

Fuse good and applying 12v to blue/red does indeed allow relay to click and fan work as it should on all settings.

Does the ignition load relay serve anything else as not noticed other failures? And can you tell me the location or if not important can I just borrow another ignition switched 12v supply to serve the blower motor relay?
Click to expand...
Download this http://www.landy.ee/manuals/electricity/Disco_Elec.Troubleshooting Manual - LRL0077ENG (1997).pdf save it and open with acrobat reader then go to "Connector" and see C2007, that's the ignition load relay which is for more functions, check te blower control diagrams too, maybe that relay is fubar... you can use other switched live for the blower if you dont have air conditioning
 
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