92 - 87 C rad fan switch?

[burgandy81]

Hi All,

Following some research on the board here I have purchased a 92-87 rad fan switch (box says Beck Arnley 201-0908, part is stamped MotoRad) as a replacement for my failing stock unit in my 81.

My understanding of this switch is that it is normally open and closes at 87C. The switch will OPEN again at 92C. In its original application this is part of a two stage fan assembly.

I have a couple of questions.

1. Is my understanding of this switch correct?
2. Is my spider likely to heat up past 92C with the fan on? My worry is that the fan will come on at 87 and the temp will continue to rise above 92 and the fan will shut off leading to potentially disastrous overheat.

Cheers,

Jordan

[courtenay]

I'm guessing here, but I'd say the opposite is probably the case. i.e. the switch will turn the fan on when the temp reaches 92 deg C and turn it off when it drops to 87 deg C. I simply cannot imagine that anyone would design a switch to do the opposite.

[burgandy81]

Thanks Bruce,

Having read your reply I feel you are right and also feel a little foolish for not having thought of that. Annoyingly the parts guy had no idea what the numbers meant and the internet was not explicitly clear.

Anyone else able to confirm this?

Cheers

[rlux4]

Hey, if that's what Bruce thinks, I'll go along.
(He's right of course.)s
Ron

[courtenay]

Careful, Ron. The sum total of my mechanical knowledge would fill a very small book - or pamphlet. Note my earlier post had words like "guess" and "imagine" in it. Thank you, though, for confirming my guess and imagination.
Cheers,
Bruce

[azruss]

simple test. you can test this yourself as i have done several times to see if T-stats were working properly. all you need is a stove, pan of water, and thermometer. put the t-stat in the pan and check the temp when it opens and closes

[courtenay]

Russ - the part here is a fan switch - the little thingy at the bottom of the rad that turns the fan on. Not sure if you can do the hot water test on it as well.

[RRoller123]

A plumber's thermometer purchased at Home Depot for a few bucks does perfectly for testing this stuff.

[Fi8spider]

Russ - the part here is a fan switch - the little thingy at the bottom of the rad that turns the fan on. Not sure if you can do the hot water test on it as well.

Good point you've raised here courtenay.
Thermofan switches can be tested with a pan of hot water, a 12v supply, a common 12v blinker globe and socket (or test light) and a couple strips of auto wire.
Wire up the blinker globe to the 12v supply though on the positive wire snip it in the middle and place the thermo fan switch in line between the 12v supply and the globe. Now drop the switch in the water and start boiling. The thermofan switch opens circuit at the highest temp rated for the switch for example in this case 92deg where the light should go on. The light will switch off as you cool the water down to lowest temp rated for the switch. You can use this method to check old switches you may have lying around in the shed or use a thermometer to check if the switch is working in the range you need if its not marked on it.

[azruss]

you dont even need a power supply, just check the switch for continuity. when it gets to temp, the switch should close and show 0 ohms. The last time I tested, i used a coffee cup and nuked it in the microwave to boiling. lowered the switch in cold and as it comes up to temp you can see it close. if you have one of those futuristic temp probe ray guns, you can check the water temp as the meter jumps. easy peazy

[burgandy81]

Thanks all,

Feel much better about my choice and learned a few things.

Love this site!

Jordan

[124cso]

A word of warning if I am not too late ???
That existing switch may have been in that radiator for 20 years or more and be well settled in. I had to pull my rad out to get to it properly and could see the tank flexing with a 12" Crescent on the switch/plug. So i had to hold the mounting boss with Pump pliers in one hand and crack open the plug with the other. It would have torn the mount out of the radiator otherwise. Used them again to fit new switch.