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help identifying an odd looking coil in the heater blower

Discussion in 'Series Land Rovers' started by JCS1991, Dec 5, 2010.

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  1. JCS1991

    JCS1991 New Member

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    in my 1981 series 3 I was replacing the heater fan (blades came off) and noticed a cylinder shaped thing inside the fan unit, the one attached to the wing, the cylinder looks (not entirely sure of this) like its a ceramic cylinder with wire wrapped around it in a spring shape, like an old style bar heater, or maybe a resistor

    its about 4 - 5 cm (just under 2 inches) long

    there is a wire coming out each end of it and these dissappear into the bulkhead

    my first guess was that its there to defrost the motor and fan blades, but I can't see how it would be controlled

    other ideas are temperature sensor of some sort (very unlikely)
    a resistor (but what for)


    its a mystery to me, so if anyone can shed some light on it I would be happy
    I could start poking around in the dashboard and trace the wires, but im not really in the mood right now and was hoping someone on here would know
     
  2. brnocz

    brnocz New Member

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    high voltage resistor almost sure its to regulate power and to stop the high temp from wiping out your heater. if you have a haynes manuel it will tell you in there,
     
  3. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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    "High voltage resistor"????
    Pray explain where the high voltage comes from?

    You have two speed heater fan - that is a high current resistor to slow down the fan on it's slower setting. There should be 3 wires going to the fan box. One is earth and the other 2 are power going to either side of that resistor. When power is applied to one line the voltage goes through the resistor, slowing the fan diwn. When voltage is supplied to the fan side of the resistor, the fan sees the full voltage and runs at full speed ( or blows the fuse if the fan is fuct).
    Ask Jps - he is an expert in heater fan control ;).
     
  4. 1396midget

    1396midget New Member

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    ^^^ WHS. Most (all multi speed) heaters have em in somewhere, must admit to being confused as to wat it was when i first saw one, thort it was some kind of weird pre-heater. it's not though.
     
  5. brnocz

    brnocz New Member

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    why is it mad hat that you never give advice or help when asked but you always jump in with negative remarks, dont bother replying as i dont read the boring comments
     
  6. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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    :confused: I merely asked if yu would explain your post as I dont understand where the high voltage comes from?
    I apologise if my explanation was too difficult for you to understand, but then, as I didnt understand yours either, I just hope that the OP understands one of them.
     
  7. oxides

    oxides Well-Known Member

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    Hmm, MHM's answer was succinct and accurate and yours was a load of bollocks in every respect - and you're feeling offended?
     
  8. nathan5346

    nathan5346 Well-Known Member

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    Yer... so come on brnocz and explain yaself :D
     
  9. nrgserv

    nrgserv Well-Known Member

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    genuinely the first post that made me laugh uncontrollably!

    apart from i'd have called it a ballast resistor, i'd say the same.
    and its in the fan unit cos it gets hot and the airflow cools it.
     
  10. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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    I concur with your words of wisdom :d.
     
  11. oxides

    oxides Well-Known Member

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    Oh dear, I feel a dose of nit picking coming on.........
    A ballast resistor is designed to limit current. In a vehicle electrical system we have a constant voltage (ish) generated by the alternator regulator and the fan needs a dropper resistor to lower the voltage at the motor to slow it down. Although it's a moot point......
     
  12. JCS1991

    JCS1991 New Member

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    hmmm seems so obvious now, I feel embarrassed for not realising what it was myself. I just assumed I had fast and slow speeds LOL
     
  13. nrgserv

    nrgserv Well-Known Member

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    Ballast Resistor

    soooo....
    why are these called ballast resistors?

    its ohms law really, and probly more professionally referred to as voltage drop across a resistance.
    and its what i've allus known em' as.

    not nit pickin tho!:eek:
     
  14. oxides

    oxides Well-Known Member

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    The coil is fed with a switched DC supply and therefore does not behave like a fixed resistance, the resistor has a damping effect in the circuit, limiting the maximum current flow so it is, technically, a ballast.
    The heater motor is fed with a fixed DC and therefore, under normal running conditions, behaves more like a fixed resistance so the series resistor acts as part of a voltage divider and is acting as a dropper resistor.

    Pass the nit comb, please.
     
  15. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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    :confused: power is supplied ( via a multiposition switch) to both sides of the resistor. Power is taken from resistor end "b" to fan and then to earth.
    If power is supplied to resistor end "a" then current glows thru resistor to fan and then earth. If power is supplied to resistor end "b" then current bypasses resistor and goes direct to fan.
    Power to "a" = reduced speed.
    Power to "b" = full speed.
    Simples....
    Where do yu get a switched DC supply from? It is a fixed Dc supply via a switch - that ain't a "switched dc" supply.
     
  16. oxides

    oxides Well-Known Member

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    Where do yu get a switched DC supply from? It is a fixed Dc supply via a switch - that ain't a "switched dc" supply.[/QUOTE]

    I'm talking about the ignition coil ballast resistor here - fed via the points. Maybe "interrupted DC" would have been a better term.
     
  17. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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    But the OP is talking about the heater resistor, not the coil resistor :doh:. Yu is muddying the water :eek:.
     
  18. nrgserv

    nrgserv Well-Known Member

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    hehe seem to be hijacking a thread here!

    mhm, soz for the confusion, you were right, we were right, we're just debating on the name of summat.
    you could join in, then we could have a massdebate.....:D

    oxides, temporary defeat here as the s3 o&m manual has everything but the resistor.
    but to be going on with,
    https://www.lrcparts.com/view_produ...ES&PHPSESSID=1b51b47ad2375179d4c007d375c20578
    this is fixed dc?
     
    Last edited: Dec 6, 2010
  19. oxides

    oxides Well-Known Member

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    No NRG was muddying the waters, I was trying to clear.....Oh sod it. Anyone know what the biggest tyre I can fit on my SWB is? :)
     
  20. thought it was mine!

    thought it was mine! New Member

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    zooport makes little britian seem posh!!!
    yea ones that fit round ones are the best!!!!
     
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