Citroen zx radiator fan to manual switching.

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Huskyxantia
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Citroen zx radiator fan to manual switching.

Post by Huskyxantia » 02 Jul 2019, 21:53

Took my old ZX estate 1994 today for its MOT. Its been off the road since 2017 and decided to take it for the test.

It passed.

I'm wanting to put the radiator fans on a separate switch .

How do you do this .

Any help
Thanks in advance :)

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white exec
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Re: Citroen zx radiator fan to manual switching.

Post by white exec » 03 Jul 2019, 08:23

Here's the standard circuit set-up for twin fans being controlled by the bank of three relays. The relays are energised by supplies from either a two-stage thermo-switch (early models) or from an ECU-fed temperature controller* (later models).
* Check polarity of this control signal, +12 or Gnd.

Either way, it is possible to manually turn on the relays (you just need to identify the Low and High speed supply lines) to give manual switching of the fans.

The circuit was originally drawn to add manual fan control to a twin-fan BX.

Hope the circuit may be of use.
Cooling fan circuit-001.jpg

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Re: Citroen zx radiator fan to manual switching.

Post by Huskyxantia » 03 Jul 2019, 08:57

Many thanks for this.
Cool , I'll study this later and source parts needed then give it a go , fingers crossed.

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Re: Citroen zx radiator fan to manual switching.

Post by Huskyxantia » 03 Jul 2019, 09:04

So when I find the low and high speed power lines do i splice these to a rocker switch for the manual operation of one or both ?
If that makes sence.

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Re: Citroen zx radiator fan to manual switching.

Post by white exec » 03 Jul 2019, 09:18

Locate the Hi and Lo signal lines, and check whether they are +12 or Gnd when fans go into operation.
Splice into those for the manual switch(es).

I don't have a ZX wiring diagram handy, but someone here might well have one.

Caution: don't modify/change the connections to the main relay contacts, as the three relays are inter-connected, and if this is done incorrectly there is a risk of a high-current short circuit.

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Re: Citroen zx radiator fan to manual switching.

Post by Huskyxantia » 21 Aug 2019, 08:23

Update,

Things seem to be fine , I unplugged the sensor on the top right side of radiator and bridge the plug and added a toggle switch correct ampage, so far I've only used it 3 times only when idling in traffic cues , watch the needle flick switch if need be.

Today I will plug it back to the sensor and see what happens .... The little saga continues

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Re: Citroen zx radiator fan to manual switching.

Post by Pug_XUD_KeenAmateur » 21 Aug 2019, 13:08

Have always found it useful to bring the revs up periodically while ticking over, which negates the need for manual fan switching.... about 1200rpm for 10 seconds or so at a time.

If I fail to do this, the recorded temperature stays fairly low, but then shoots up to 95c once I'm back underway, at which point of course the fans come in & get things back to normal.

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Re: Citroen zx radiator fan to manual switching.

Post by Huskyxantia » 23 Aug 2019, 10:29

Pug_XUD_KeenAmateur wrote:
21 Aug 2019, 13:08
Have always found it useful to bring the revs up periodically while ticking over, which negates the need for manual fan switching.... about 1200rpm for 10 seconds or so at a time.

If I fail to do this, the recorded temperature stays fairly low, but then shoots up to 95c once I'm back underway, at which point of course the fans come in & get things back to normal.
A good idea I've done this a few times even the water pump needs a little kick now and again, and its only 2500 miles old !