Radiator Fan Run On...

[bacardincoke 42 1 Cars]

Can't imagine anyone doesn't know as it's been done to death on another post but incase not... My '89 1.9 has the twin fan and radiator set up from a TD, including the correct relay box etc. etc.

 

I'm confident it's working perfectly, insofar as the cooling side of things go.

 

I've only recently realised that if the fans were running just before switching off the ignition, the fans stop too. I'd have expected them to keep going to finish their cycle.

 

It varies but if you switch on again without starting they can keep going (in low speed) for anything up to a few minutes.

 

I'm not experiencing any coolant problems at all, the car's running sweet as a nut at the moment.

 

I can't find it again but there was another very old post on here where someone was discussing the opposite (the fans running on when the ignition is off)... Another poster mentioned that this was normal for all engines except A/C equipped and Diesel ones.

 

Is this correct... May explain why my TD set up does it?

[2052006 10]

Mine, to which I have recently fitted a TD relay setup, operates exactly the same way.

 

Conversely, my old setup (original) used to run on with ignition off, like you say.

[welshpug 1,621]

yes this is correct as they use an ignition switched live, single fan are permanently live standalone from the ignition.

[bacardincoke 42 1 Cars]

Is there a technical reason for the difference?

 

I'd have thought if the engine, be it petrol / diesel or one with A/C reached a temperature that brought the fans on, it would need them to continue to run to the end of their cycle, aiding cooling. Shutting off too soon must be hard on the engine.

 

Is it the normally redundant red socket behind the washer bottle that's the ignition live for TD fans?

 

Would it be beneficial for me to have mine revert to permanent live?

 

At the moment if they're running when the car's going to be turned off I leave it on accessory for the few minutes it takes them to end of their own accord. No big deal, but it'd be handier not to have to.

 

 

[bacardincoke 42 1 Cars]

Anyone any thoughts on this?

[Ryan 99]

Yes it's the red plug that powers the fans. One pin is a switched live and, the other pin goes back to the fusebox but isn't connected to anything (maybe used on cars with a/c?).

[bacardincoke 42 1 Cars]

Cheers Ryan... That answers one question, still seems odd Peugeot would differentiate between models as to how / when the fans come on.

 

I'm new to these cars but one thing that seems to crop up frequently when reading old posts is their susceptibility to overheating damage, curiosity's got me wondering why the TD / AC way of doing it.

 

Like I say everything's working 100% and presumably also as intended so no plans to start changing anything plus it's seldom the fans are running on shut down in any case.

 

 

 

 

 

[stewal 7]

My car has the twin fan set up as standard and can confirm that the fans turn off with the ignition.

 

I suspect the reason for this is the twin fan set up uses a very clever system of 3 relays which either connect the fans in series or parallel creating the 2 speeds.

 

I guess peugeot didnt want the relays to be permanently live which is sensible because they would be more likely to fail.

 

In the standard car I dont think the fan is  relay controlled but is live via the thermostaic switch. This means the switch has to carry a large current when the fan runs and is prone to failing as a result.

 

With our set up, the switch carries very little current thanks to the relays and should be much more resilient. 

 

In addition, the twin fans will be much more efficient in cooling so I guess there would be less of a need for them to run on after the engine is stopped.

 

You have probably never heard the fans run at high speed: they sound like a Hovercraft when they do and the engine temp drops really quickly! 

[bacardincoke 42 1 Cars]

Thanks... I've since tried to recreate the conditions were the fan(s) cut in so as to better understand how they behave.

 

You're right... under normal conditions the high speed has yet to kick in at all. Like you say, you'd definitley know by the sound when it's on.

 

Might explain why Peugeot thought to fit the test plug... probably the only time owners heard the fans on high and needed convincing they worked!

 

Now that I've been paying more attention, the low speed doesn't come on at the end of a drive... it really only occurs after you've stopped, but allowed the car to idle for a while.

 

I know the gauge readings are to be taken with a pinch of salt, but if it's even reasonably accurate the highest it's ever gone in all situations has been midway, so I'm more than happy things are working as they should.