505 SLi electric clutch fan setup
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  1. #1
    Member blizzardboy's Avatar
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    Default 505 SLi electric clutch fan setup

    I am fixing up a few things on my recently acquired 1986 505 SLi wagon. After finding that someone had previously permanently locked up the electric clutch on the cooling fan, I have resurrected it. I found a second hand brush and holder, cleaned up the slip ring, adjusted the gap and away we go.

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    I do have one concern however. I have been led to believe that there should be a diode in the power wire supplied to the clutch (via the temperature switch on radiator) to prevent current generated by the free spinning fan flowing back into the fuse board. If this is the case, where is the diode and how do I test it?

    Is there anything else in the electric clutch setup I should check (apart from the correct engaging of the fan) before I drive the SLi?

    Thanks in advance for any assistance.

  2. #2
    1000+ Posts robmac's Avatar
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    Default Diode For Clutch

    Quote Originally Posted by blizzardboy
    I am fixing up a few things on my recently acquired 1986 505 SLi wagon. After finding that someone had previously permanently locked up the electric clutch on the cooling fan, I have resurrected it. I found a second hand brush and holder, cleaned up the slip ring, adjusted the gap and away we go.

    I do have one concern however. I have been led to believe that there should be a diode in the power wire supplied to the clutch (via the temperature switch on radiator) to prevent current generated by the free spinning fan flowing back into the fuse board. If this is the case, where is the diode and how do I test it?
    Is there anything else in the electric clutch setup I should check (apart from the correct engaging of the fan) before I drive the SLi?

    Thanks in advance for any assistance.

    Hi Blizzard

    If you are using the standard Peugeot setup . That is, the switch in the bottom of the radiator controlling the engine fan clutch . No diode is required because the clutch winding ( is like an electromagnet) it is not a motor and not will generate voltage.

    The aircon condenser fan will need a diode (or relay) if it is connected to run with the aircon compressor clutch. The fan generates voltage when run by air movement and can pull in the compressor clutch.

    Personally I would use a relay because reduces the current through the aircon thermostat - without a relay both the compressor clutch and condensor fan are switched through the thermostat.

    One more (optional) use of a diode is to arrange the engine fan engage when the aircon compressor at comes on but not vice versa. This is some in very hot climates.


    regards

    Rob

  3. #3
    Member blizzardboy's Avatar
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    Default Two outputs on thermoswitch

    Hi Rob,

    I already started another thread on this subject (I am never sure how many threads to start!?). Thanks for the advice on the electromagnet not being a motor.

    What I am confused about is that the thermoswitch has two outputs: one to the electromagnetic clutch for the radiator fan, the other I am not clear on its purpose. If I pull the plug off the thermoswitch and supply 12V from the battery to the wire which plugs onto that 'other' output, the A/C clutch locks up.

    Does that seem right?

    I understand that the A/C fan is meant to come on in the event of the radiator fan failing. Do you know how this two output (three pin) thermoswitch is meant to operate?

    Cheers, Todd

  4. #4
    Gone Fishin' Ray Bell's Avatar
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    Default

    Like I said in the other thread, I think you're feeding power back up a wire that usually has power come down it, if you know what I mean.

    In other words, the wire you're putting the power to that makes the air con clutch work is normally feeding power to the fan clutch when the air con is on. Turn on the ignition and the air con and see if you have a live wire there...

  5. #5
    Budding Architect ???? pugrambo's Avatar
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    Default

    have you hot wired the thermo fan to make sure it works ?

    you will also have a fuse for this fan as well so make sure that it isn't blown as they blow very easily once the fan is dead
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  6. #6
    1000+ Posts robmac's Avatar
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    Default misleading info about thermo switches

    Quote Originally Posted by blizzardboy
    Hi Rob,

    I already started another thread on this subject (I am never sure how many threads to start!?). Thanks for the advice on the electromagnet not being a motor.

    What I am confused about is that the thermoswitch has two outputs: one to the electromagnetic clutch for the radiator fan, the other I am not clear on its purpose. If I pull the plug off the thermoswitch and supply 12V from the battery to the wire which plugs onto that 'other' output, the A/C clutch locks up.

    Does that seem right?

    I understand that the A/C fan is meant to come on in the event of the radiator fan failing. Do you know how this two output (three pin) thermoswitch is meant to operate?

    Cheers, Todd
    Hi Todd,

    I think I may have mislead you. I was under the impression that all 505 thermo switches have had only one set of contacts, for the engine fan clutch.

    It appears that some 505s have three terminals (two sets of contacts) on the thermo switch from what Ray says.

    If this is correct then there is a common (power via fuse +ve) and one terminal goes to fan clutch and the other to the radiator fan (is this the fan in front on the a/c condenser ?).

    The rationale of this is probably two temperature switch points
    1) for clutch on engine fan
    2) electric fan (set a bit higher)

    If the electric fan is also switched by a/c compressor clutch you will need a diode to stop the electric fan spinning and pulling in the a/c clutch.

    At this stage can we have some expect advice from other forum members about three terminal 505 thermo switches and how they work ?

    The above is only a guess and there are definitely people in the forum who will know exactly how things work.

    As to threads - the way I personally work it is to keep the threads to minimum once the inital topic has been presented and just keep posting. I will start a new thread if there is an aspect which is very specific is raised and I want to know more. Sometimes threads become very unruly and too long -then it's worth starting again - but wait for a while - everyone gets bored about one topic ad nauseam! You know when this happens because the thread stops getting posts!

    regards


    Rob

  7. #7
    Gone Fishin' Ray Bell's Avatar
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    Now electricity gets me a bit... I don't really know all the ins and outs of it... but it seems to me that there must be a reason for a wire to run between the A/C and that switch.

    Is it possible that there's some kind of a one-way device in there so that turning on the fan doesn't turn on the compressor? In which case what I suggested above would be the natural function, that both turning on the A/C or getting up to the thermo level would turn on the fan.

    Then another possibility... could it be that reaching fan temp switched off the A/C as in other cars?

  8. #8
    1000+ Posts robmac's Avatar
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    Default One Way Device

    Quote Originally Posted by Ray Bell
    Now electricity gets me a bit... I don't really know all the ins and outs of it... but it seems to me that there must be a reason for a wire to run between the A/C and that switch.

    Is it possible that there's some kind of a one-way device in there so that turning on the fan doesn't turn on the compressor? In which case what I suggested above would be the natural function, that both turning on the A/C or getting up to the thermo level would turn on the fan.

    Then another possibility... could it be that reaching fan temp switched off the A/C as in other cars?


    The "one way device" is called a diode .

  9. #9
    Budding Architect ???? pugrambo's Avatar
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    the thermo fan will run through a relay and be fused in the fuse box

    the engine fan i don't think has any of this

    from memory 504's with A/C had the engine fan triggeredfrom a sender from the head and the thermo fan was triggered by a temp switch in the radiator

    now the XN heads from memory have the temp guage switch at the rear of the head which to me is wrong as it's the coolest part of the engine anyway...........

    make sure the engine fan kicks in when powered and the thermo fan operates when hot wired

    then check fuses and relay contacts

    the engine fan kicks in at a lower temp than the thermo fan and the thermo fan also kicks in whenever the A/C is turned on

    to check the 3 way switch in the radiator you will need to run the car and run a meter on the switch or even just a simple test light setup to see what side switches in what order

    you also may be able to do this in the stove but please don't get burnt
    3 x '78 604 SL

    1 x '98 306 GTi6

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0


    WTD long range fuel tank for 605

  10. #10
    Member blizzardboy's Avatar
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    Default problem solved

    Well its been a fun problem to solve, but I have finally worked it all out.

    Firstly, thank you to everyone who offered me advice. I really appreciate it.

    While I had the radiator out I tested the thermoswitch on the stove. There are two temp ranges stamped on the side of the switch: 88/84 and 92/88. The lower range applies to the clutch fan and the higher to the A/C fan. Once heating on stove, the switches kicked in pretty much on cue and then, with the gas off and the water temp cooling, kicked out to plan. The only issue was that the lower range switch was wobbling around 3 Ohms when closed.

    Worried about the resistance of the lower range switch, I went out to the car to test the thermoswitch in its native environment. After setting up my Trangia, a pot of water, a thermometer, an upside down sardine tin and some creative wiring, I found the clutch to closed up on cue.

    After reinstalling the cooling system (including a rebuilt coolant level switch - but that's another story), alas the clutch no longer kicked in. However, when the temp rose high enough the second switch closed and the A/C fan kicked in nicely. Cycled away on the A/C fan as happy as Larry.

    By removing the connector to the thermoswitch and adding in some bridging wires, I wired up the clutch fan to run on the upper range (A/C) switch. Worked a treat. So I then knew that I indeed needed a replacement thermoswitch.

    Gary at Pugparts sold me a secondhand one, I tested it (good in both ranges) and then put in the radiator. Clutch fan kicks in nicely now.

    As I said before, when I bought the SLi the electromagnetic clutch fan was locked up. My guess is now that the car was running hot as a result of the dodgy thermoswitch so someone bypassed the problem by locking it up.

    At first it was a bit unnerving to see the temp gauge sit higher (now about midway) but great to hear the quiet start, see the quick warm up, watch the fan cycling on/off, and feel the better drive when the fan is not running full bore. I took the car for a good run on the freeway (100 km/h) and the temp behaved nicely.

    Another little note from this exercise, is the importance of setting the 0.3mm gap correctly on the clutch fan. When hot this gap closes up; If the gap is set too small the fan would be locked on fulltime once the engine reaches running temp.

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