Coolant fans conundrum

[Adamstanford 3]

Hi all, car is a 1.6 gti, runs perfect, temp used to get to a click over half way on the gauge then the fan would cut in. 

 

I replaced the rad, and the fan temp switch was weeping so replaced that too. 

 

Now, the car temp never goes above half, and in town driving the fan cuts in a lot (in this hot weather) and stays running a few mins after turned off. 

 

So its not overheating but the new switch seems to make the fan cut in earlier. Not the second fan. 

 

Is this a cause for concern or should i get a bigger alloy rad like the 40mm direnza?

 

Car doesnt get driven hard atall, im very mechanically sympathetic and its my wee pride. 

[welshpug 1,655]

either the new switch is lower switching temperatures or the old one had failed on the low speed circuit.

[Adamstanford 3]

3 minutes ago, welshpug said:

either the new switch is lower switching temperatures or the old one had failed on the low speed circuit.

I didn't think of that second point! Thanks. Nothing to worry about with the frequency of them coming on? Temp never goes up. 

[stewal 8]

Trouble with the fan switches is that there is such a variety of switching temperatures as the location of them varied in the rad (some high up, some lower down): which is why there are blanking holes on some rads.

if you still have the original switch, the temps should be stamped on the side on one of the flats: low speed cut in and out, high speed in and out, would guess the replacement cuts in at a lower temp. Not a problem this time of year but guess it will overcool in winter.

[Tom Fenton 1,540]

Rad fan switches are identified by coloured bands, standard for a GTI is a red coloured banded switch.

[jackherer 543]

36 minutes ago, stewal said:

Not a problem this time of year but guess it will overcool in winter.

It wont over-cool if the thermostat is working, the airflow from the fan is just the equivalent of driving at 20-25mph.

[Anthony 1,002]

9 minutes ago, stewal said:

Not a problem this time of year but guess it will overcool in winter.

 

Over-cooling won't be an issue - thermostat controls the running temperature, and the fan switching temperature should always be above the point at which the 'stat is open.

 

As Tom said, standard GTI thermoswitch is red banded which has a switching temperature of 97/102 degrees for the slow and high speed fan respectively.  I've run the cooler purple banded switch (found on later XUD's etc) without issue - that one is 92/97 degree from memory, and results on the slow speed fan coming on a touch over halfway on the gauge.

 

On 7/12/2019 at 7:11 PM, Adamstanford said:

Is this a cause for concern or should i get a bigger alloy rad like the 40mm direnza?

 

The slow-speed fan cycling in slow moving traffic on a warm day is perfectly normal and not anything to be concerned about - only if the temperature continues to rise and you're seeing prolonged periods of the high-speed fan running and/or the fan is coming on when moving at speed in free-flowing traffic would I be investigating to see what's amiss.