ZX high speed rad fan doesn't work

[bv2991]

Hello fellas,

My ZX's radiator fan only runs on low speed. Wouldn't engage high speed when temperature reaches 90deg C.

Car's for Malaysia model. Factory Air-con, twin fans.

I've tried:

a) Swapping fan relays.
b) Bypassing the high-speed wire on top of the aircon drier cylinder can.
c) Topping up air con gas (previously it worked).

I was told that there's a sensor behind the water thermostat housing that's related to this as well. How do I check if it's working or not?

Appreciate any advice. Thanks a lot in advance.

[Clogzz]

Don’t know about the air-conditioned ZX, but hope that it’s got much in common with its relatives of that vintage.
The brown sensor on the thermostat housing controls the cooling fans.
When you disconnect it, both fans should go to high speed.
We have a lot of topics about the Xantia cooling fans.

This link gives a good explanation:
http://www.peugeotlogic.com/workshop/ws ... fanop1.htm

[CitroJim]

90 degrees seems a very low temperature for the fans to cut in at high speed. Low speed yes, but they should not do their impression of a cyclone until the coolant is much hotter...

Intrinsically, if the fans run at low speed then they are OK in themselves as they are in series. For high speed they switch to being wired in parallel.

[bv2991]

Thanks guys,

Clogzz, I've tried disconnecting the brown sensor behind the thermostat housing, and nope, the fans stayed at low speed. Could this means that it's the culprit?

Citrojim, it wouldn't engage high speed even when the temp hits about 95dec C.

I guess I should just bring the car to a specialist eh?

Cheers!

[Clogzz]

The brown sensor isn’t likely to be faulty.
Do the fans go to low speed from cold, or only after warm-up when required, even with the air conditioning turned off ?
Being in Malaysia, hasn’t the air conditioning been permanently hard-wired to function all the time, to make up for an engine cooling fault ?
Do the relays look like this ?

[bv2991]

Err well,

Upon start-ups, with A/C off, the fans wouldn't turn. When the temp reaches 90dec C on the gauge, they'll run automatically.

But, turn A/C on and the fans will run right away regardless of engine temperature.

Usually, I'd top-up the refrigerant and it'll run at high speed as normal. This time, no. So, we tried bypassing the refrigerant pressure switch on top of the drier cylinder, still wouldn't engage high-speed when it should.

Yup, the relays look like in the pic.

I'll consult a specialist workshop soon. Will keep you fellas posted.

Cheers!

[Clogzz]

Low speed must only come on when the engine gets hot enough to need cooling.
Even in ambient temperatures around 30ºC, the fans should be off if the car is moving at more than about 40 km/h.
Turning on the air conditioner switches on the fans at low speed for all the time that the air conditioner is on, to cool the condenser.
High fan speed is to cool the engine when it gets close to overheating, or when there is overpressure in the air conditioning.
Topping up the air conditioning may cause overpressure.
My air conditioning is low on gas, but still turns without putting out any cold.
As a sort of rule, you may take that the pressure is still sufficient if it puts out any useable cold.
If topping up now no longer causes high fan speed, it may mean that you refilled from a lower charge, or didn’t refill to the same charge.
Can’t explain why disconnecting the brown sensor or shorting the overpressure pins doesn’t send the fans to high speed.
A possibility is that the bottom and left relays don’t get energised for the high speed, due to an open wire from the Bitron control box.

[bv2991]

Yikes!

Could this mean that the Bitron box is kaputt?

I've yet to take the car to the specialist, but still, I appreciate your kind advice. Your explanation is quite detailed, yet easy enough to understand.

Have yet to verify the Bitron box and the brown sensor. Will update later!

Cheers!

[bv2991]

Hiya fellas,

Well, took my ZX to the Citroen/ Pug specialist today to fix the fans problem.

After fiddling with the relays and overpressure switch (just to make sure), then replacing the Bitron control unit, the fans roared at high speed!

It's definitely the Bitron unit because disconnecting the brown sensor and shorting the overpressure wires doesn't put the fans into high-speed. We replaced the Bitron unit but it didn't work at first!

After fiddling with the brown sensor and the relays, suddenly one of the fans went into high-speed. After a few more tries and checking the current flow, both fans went into high speed. It's like after changing the Bitron, the car's re-learning the parameters and took a while before correcting the fault.

So, in the end, I replaced the Bitron box and 2 fan relays just to be safe.

Well, at least I'm much happier now, not having to worry about refrigerant leaks after a few drives in hot Malaysia noon anymore.

Thanks a lot to you guys, especially Clogzz and Citrojim!

P/S: Clogzz, whereabout in Australia are you by the way? I did my degree 'down-undah' from 1993-1996.

[Clogzz]

Oops ! I missed your post of last week.

Good to read that it’s fixed, and hope that it will last, because there are some curiosities in this fix.
The Bitron has a single output for the high speed of both fans, so cannot cause only one fan to run at the high speed.
Neither does it have a learning capability; it’s controlled by the coolant temperature, the air conditioning on-function, and the refrigerant pressure.
The Bitron can have bad connections though, mostly on the input side, and replacing it, or just disconnecting and reconnecting the dodgy contacts may clean them.

I’m in Palm Beach on the Gold Coast, in gaudy Queensland.
Palm Beach sounds like a fabulous place from the distance, but in fact it’s an old slum area, made up of shacks built of wood, asbestos and corrugated iron.
We think that we are better than that, because we live on the fringe, near the snootier ‘Elanora’.
They're in the process of pulling down the old slums to build ‘better’ places, so the yobbos are losing their habitat.

It’s too hot and sticky in summer here, 30ºC every day for over three months.
We’ve been here four years, and were in Sydney before, though I’m a native of the French-speaking part of Belgium.

http://en.wikipedia.org/wiki/Palm_Beach,_Queensland

[bv2991]

Yup,

I was flummoxed myself at first, after replacing all the relays, fiddling with the overpressure switch and disconnecting the brown sensor, no response.

So, the mechanic checked each terminals for the relays, wires and switches for presence of current, after changing the Bitron box. Nothing happened at first. While he was fiddling with the relay, then one of the fans went into high speed. Went on fiddling with the overpressure switch and thermostat sensor and Voila!

Even the mechanic was as flummoxed as me! Driving home in the evening, the fans went into high-speed at intervals. As the night comes, they maintained low-speed due to cooler ambient temp.

Today, under the stinging sun (it's really hot today!) I ran the engine and Aircon at my office's parking for about half-an-hour and the fans were running at high-speed mostly, cutting out to low speed at intervals. Later, after office, they ran mostly at low speed.

I suppose these were correct behaviour of the fans? The aircon is noticeably much cooler under the hot sun too.

So, you're in Gold Coast eh? If you're complaining about the heat, I used to complain about the chill as I was in Armidale NSW (New England). Even the locals were complaining about the climate!

Plenty of stories about Australia, but maybe I should PM you ha ha.

Once again, thanks fellas!

[Clogzz]

Yes, normal behaviour for the fans to switch between high and low speeds when idling in the heat with the air conditioning on.
The refrigerant pressure increases as the condenser gets hotter, and so does the engine, and the fans go to high speed.
The air conditioning was cooler because the high fan speed was cooling the condenser more effectively.

The relay faults were either bad coil contacts, or sticking relays.
If the coil contacts are intermittent, there will be no traces on the terminals because the drive current is low.

The relays can also stick shut, as I’ve had, and also came good by itself.
The bottom change-over relay can stick in the non-energised position, which is used at the low speed, and has the fan current going through it even in the released position.

I remember Armidale’s cold weather from passing through there.
Further north, near Glen Innes, at an altitude of about 1,000 metres, it was snowing.
Disgusting to slosh around in the snow when going to live in Australia to escape the cold.