Testing Cooling Fan Switch

[mikeygulley 19 1 Cars]

Hi,

 

Driving to work this morning I got stuck in traffic and the coolant temp on my 6'd 205 got higher than I would have expected but didn't over heat. It got up to between the last 2 thick lines on the gauge, I haven't had it this high before. It didn't climb any higher than this but sticking my head out the window to listen for the fan wasn't much cop!

 

Anyway I dropped my bro off at work, by then the temp had dropped to just below the 2nd to last thick line. When I stopped the fan wasn't on. I then decided to cross the wires on the 3 pin 'test' plug, the fan came on on both blue and white (I removed slow speed resistor some time ago).

 

My question is does this actually tell me if the stat in the rad is OK or would it work even if faulty??

 

I did change the expansion cap recently to 20psi, so running at a slightly higher pressure to the standard 15psi.

 

Thanks in advance.

 

Mike

[Tom Fenton 1,542]

The test plug proves everything except the switch is working, so it checks motor etc is OK.

[mikeygulley 19 1 Cars]

OK cool, I will let it sit this evening to see if they come on. Sure I have a spare somewhere!

[mikeygulley 19 1 Cars]

thermo switch changed this evening and all is good again

[starky5 18]

Digging this back up as I have a similar problem, where is the thermo switch and how can you test it? My fan doesn't kick in but I've tested it and it works

[Goliath 94]

Digging this back up as I have a similar problem, where is the thermo switch and how can you test it? My fan doesn't kick in but I've tested it and it works

It's in the side of the radiator. To test it you can take it out, put it half into a kettle of water and bring to the boil, the fans should kick in before it boils. It will say on the shoulder of the sensor what temp it is meant to activate at.

[welshpug 1,657]

or just buy a new one, they're about £12.

[Anthony 1,003]

or just buy a new one, they're about £12.

This. If you're in any way doubtful of it and you're going to have to remove it to test it anyway, just replace it with a new one.

[starky5 18]

Ok ill pick a new one up and see if it solves the problem! Are there any particular brands to look for with the new switch? I've had a load of problems with crap quality parts lately!

[farmer 328 1 Cars]

Ok ill pick a new one up and see if it solves the problem! Are there any particular brands to look for with the new switch? I've had a load of problems with crap quality parts lately!

 

Go genuine!

[welshpug 1,657]

no problems with the ones I've used from my local motorfactor, facet iirc!

 

have a search on the forum using the term "intermotor" I posted several part numbersrecently that any motorfactor can cross reference and all the temps for standard and slightly lower are shown.

Edited July 11, 2013 by welshpug

[TooMany2cvs 65]

Definitely just bin it and replace if you're unsure about it - but make sure the temp range is the right one.

 

I've also had one suddenly fail closed before. I walked past the Saab parked up in the snow one day - it hadn't even started it for a couple of days - and the fan was going full speed. WTF...?

[starky5 18]

 

Go genuine!

I had just assumed they wouldn't be available! Ill pop into my local dealer tomorrow, do you know if mi16 thermostats are available? I'm not sold on the quality of my current one as it was in a plain unbranded box.

 

Thanks welsh pug ill have a search and read up on the different options

[starky5 18]

I've just had a quick read of your thread with the part numbers welshpug. I'm not the most clued up on different temp stats etc. Now is if as simple as if I want the engine to run cooler I put in a lower temp stat? And if I was the fan to kick in at a lower temp then I pick the switch with the lower switching temp?

 

Are there any down sides to it coming in at a cooler temp? In my mind the cooler the better?!

[welshpug 1,657]

Theres no harm in going down a little bit, i run the 83 deg stat rather than the original 89, similarly i have a 92 deg fan switch rather than 98 iirc.

 

Theyre all o.e spec bits from other pug or citroen vehicles.

 

These engines (and most internal combustion engines generally!) Run best at around the same mid 80's, so dont be tempted to ditch the stat, even race engines that sandy and others build still have thermostats, as they run much more efficiently and cleaner, and this last longer!

[starky5 18]

That's makes sense, I don't suppose you have the part number for your 83 stat? I had a mission to get hold of my current one but I was in a rush as it was the only thing holding up my engine swap! So I have no idea what temp it is

[welshpug 1,657]

No need for a part number, just get down your local motorfactor.

[farmer 328 1 Cars]

1338 37

01

ENGINE WATER THERMOSTAT

82 DEG (83 DEG)

VERNET -

Edit

You will need these if you go genuine I would think.

1339 10 * 2

Edited July 11, 2013 by farmer

[starky5 18]

I seem to know more than my local motor factors half the time! They never seem to be able to find if the part is for the mi16 or the 8v 1.9. Will pop in tomorrow and see what i can find tomorrow morning, need to get this sorted i dont like getting so nervous in traffic haha

[welshpug 1,657]

i missed you said its a 6, theyre 83 deg as std.

[starky5 18]

It's mi16 rather than a 6, are they still 83 standard?

[TooMany2cvs 65]

Now is if as simple as if I want the engine to run cooler I put in a lower temp stat? And if I was the fan to kick in at a lower temp then I pick the switch with the lower switching temp?

The engine has a "normal running temp" band.

 

The lower end of that is managed by the 'stat. If it's too cool, then the 'stat closes and it warms up.

The upper end is managed by the fan switch. If it's too warm, the fan comes on and helps it cool.

Are there any down sides to it coming in at a cooler temp? In my mind the cooler the better?!

Definitely not that simple!

 

If the 'stat is too cool, the engine won't be at optimum efficiency. The "choke" might be on a bit, so you'll use more fuel. The heater will be much less efficient. I chucked an 83deg 'stat in my old Saab instead of the normal 89. Two weeks later, I chucked an 89 back in.

 

If the fan switch and 'stat are too close together, then you'll have the fan on too often, quite possibly overlapping with the 'stat closing.

Edited July 12, 2013 by TooMany2cvs

[Anthony 1,003]

One other consideration if it's a 1.9 Mi16 and you're still running the rear coolant rail that runs across the back of the cam cover - this won't work properly without the correct 1.9 Mi16 thermostat fitted. If you're not running that, then a regular 1.6/1.9 8v thermostat fits fine

[welshpug 1,657]

derp, quite confusing, the o.p was a 6

 

1.9 MI as Anthony said has a two stage thermostat, 1338 03, probably will be more expensive than most, seems like its used by a few older pugs and some nissans talbots and rovers, 88 degree.

 

[starky5 18]

Sorry I forgot I had hijacked an old thread! I did get the correct stat when I fitted the engine with the extra bit to control the rail round the back of the head. So I'm guessing that must be an 88 degree stat then. I have just picked up a thermo switch that cross referenced with the 50092 intermotor one. Should this be alright or in confusing you all have I confused myself and bought the wrong one?

 

It's a phase 2 1.9 gti to start with which I then fitted a 1.9 alloy block mi16 which I'm still running the cooling pipe round the back of the head