Fan thermo switch; is this right? (cheap FIX?)

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Roady
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Fan thermo switch; is this right? (cheap FIX?)

#1

Post by Roady »

Revised 28 July 2008. Please read my advice in This Post. I no longer believe that the cheap mode is profitable.

Cycleman used his scientific method to break down an Alternative Fan Switch. Read his string of posts if you really want to do this. Cost is about the same as OEM. 5 Feb '09.

Mark King came up with a way to Repair a Switch. This might be worth a try. 11 Aug '11
___________________________________

Am I doing this right?


I'm not getting any action out of the fan or temperature gauge. The gas gauge is working correctly.

Starting with the fan switch ... The radiator has been removed and the fan runs good when directly connected to the battery. So I pulled the switch out of the outside part of the thermostat housing (the one with two poles on it). I hung it in engine oil, clipped on the candy timer (yeah, it's okay, the wife is out at the stable playing with her horse) and cranked up the heat.

[attachment=0]fanswitchtestfd2.jpg[/attachment]
My tester is set on 200 ohms resistance. The Haynes manual says:

Switch open (no continuity) from 198° to 207° F
Switch closed (continuity) from 208° to 215° F

I checked from 175° all the way up to 250° and there was no change on the tester.

So, are my tester settings correct? Is the switch bad?

Later that day ... ...

Still no luck on the fan switch test. With both leads moved down one hole I get a reading of 0.3-0.2 when touching the leads together. But still no movement when testing the switch.

Good news is ... I pulled the temperature sensor and tested that (as long as I got the kitchen to myself :twisted: ) and as the temp went up the ohms went down. Not exactly the same numbers as the book but close. Mine were running about 10 higher. That prolly means wiring to the gauge or the gauge itself, eh?

But I'm still confused about the fan switch test. My Haynes manual says, "Test the switch by using a similar method to that detailed in the previous Section for the temperature gauge sensor switch and check that the temperatures at which the switch opens and closes correspond with those given below.
"Switch open (no continuity) from 198° to 207° F
"Switch closed (continuity) from 208° to 215° F
"If the reading obtained differ, then the sensor switch must be renewed."


I love the part "using a similar method". And what about below 198° and above 215°F?

But, I'm not getting any readings at all. Am I reading too much into this? It should just indicate ON/OFF, right? Maybe I need a palm reading. Let's all go jump on the Reading Railroad.... crying1
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Alley Kat
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#2

Post by Alley Kat »

I'm guessing the ranges mean that the switch should close (operate fan) at some temp between 208 and 215, and should open again (shut off fan) at between 198-207. Unless someone else knows different - 208 for 'close' seems way high, that's 97 deg C??
My book doesn't give ranges just a logic test of fan & switch.

I'd say your switch was duff, same as mine. Someone butchered mine to fit a manual fan override :roll: Tested mine in heated water, no joy.
hth
cheers
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taunusrainer
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#3

Post by taunusrainer »

Your meter is plugged wrong. :!: The black wire always must be in COM, the red wire must be above the black. Where You have plugged the red wire is ONLY for measuring strong currents up to 10 amps .
If Your switch won't close at about 210°F then it is dead. That happens often. Ford has a (Escort) switch that replaces it if Honda is too expensive.
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#4

Post by jacknj »

taunusrainer wrote: If Your switch won't close at about 210°F then it is dead. That happens often. Ford has a (Escort) switch that replaces it if Honda is too expensive.
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Ray
can you offer any specifics on that switch? mine is toast as well and i'd like to replace it.

-j
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#5

Post by taunusrainer »

It is fom an 1.6l Escort with injection, I can place a pic tomorrow. I unscrewed it from an engine lying around on the junkyard. It was mounted to the intake manifold.
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#6

Post by Roady »

taunusrainer wrote:Your meter is plugged wrong. :!: The black wire always must be in COM, the red wire must be above the black. Where You have plugged the red wire is ONLY for measuring strong currents up to 10 amps .
If Your switch won't close at about 210°F then it is dead. That happens often. Ford has a (Escort) switch that replaces it if Honda is too expensive.
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Ray
Thanks, Ray. Whiskerfish straightened me out on the connections when I originally asked in the other thread. But it was still a no go.

I'd like to get the info on the Escort part, too. Best price I can find is $40 for the Wing one. I don't want to go to the manual switch, that sucks, errr blows, IMHO.
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Last edited by Roady on Fri Sep 18, 2009 12:40 pm, edited 1 time in total.
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#7

Post by 05c50 »

Careful with that Escort thing.... an Escort in Europe is a completely different car then an American Escort. There might be a switch that will work, but you'll have to figure out what engine it is from.
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taunusrainer
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#8

Post by taunusrainer »

Yes, that is right. Escort and Escort is not the same.
But another thing: Every gasoline engine has about the same operating temp range, because nowadays they all use more or less the same coolant and have a radiator cap that produces the same pressure.
Fan switches have all a switching temperature which is between 95°C and 100°C. Modern coolant boils at 110°C (under pressure).
Typical thermostat full open temperatures are 87°C-92°C.
:idea: In short words: Simply go to a junkyard or car parts store and buy a fan switch which has the same thread.
I believe Goldwings have M18x1.5, but that is not 100% sure
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#9

Post by rcmatt007 »

just remember about aftermarket switches they aint all the same.... sabre cycle slls some that have a different operating temp... then he sends you rude emails when you want your money back....
$40... less then a dinner out
$40.... 4 1/2 viagra pills
$40.... cheaper than an ebay engine
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#10

Post by taunusrainer »

I know there are temp switches with different switching points, don't know what they are normally used for. A fan shall not work while the vehicle is normally moving, so the ON temperature MUST be above the opening temperature of the thermostat, i.e. above 95°C. Otherwise it would run always.
All fan switches I ever seen are mounted on the top of the engine/intake manifold or the top of the radiator, where the hottest area is. They typically kick in shortly before the coolant boils, that is at 110°C with 1bar pressure in the system.
That is why they all should switch on at around 100°C.
I think it is harder to find a fan switch that works at lower or higher temp than to find a 100° type.
That is what I learned on the junkyards where I used to spend a lot of time.
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#11

Post by pdafreak »

I purchased one of Saber Cycles temp switches and it worked fine, right in the range it was supose to. Only trouble I had with it was the prongs were a little farthur apart and the rubber plug/boot did not want to fit on.

And in your test the switch should go from no continuity to continuity just like a regular on/off switch. On your meter, it should be the same as leads apart or leads touched together.
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#12

Post by Roady »

Thanks, pdafreak.

I figured it wasn't any good when I put the temp gauge sensor unit in the test lab and it responded to the changes.

So, I should leave the meter set the same when testing either sensor?
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#13

Post by pdafreak »

Meter should be set to read ohms. On the temp sensor you will see the ohm value change as the temp rises. On the switch it should look like an open circuit when the temp is low, like having the leads apart not touching anything, and close to infinity, or very close to what it looks like when the leads are touched together.

You can also check your fan circuit, just jumper the plug that goes to the temp switch and the fan should come on.

The temp gauge is a completly different circuit. If your temp sensor is working your guage may be bad or you may have a bad connection.
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#14

Post by Roady »

That is excellent, pdafreak.

I have been waiting almost a week for that basic, understandable explanation.

Very much appreciated, yer my hero.
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#15

Post by Roady »

Okay, I finally got it.

Thanks to Whiskerfish, PdaFreak and Hobie1! You guys are fantastic and these forums are great.

I drug out all my paraphernalia again, got the meter set up right and boiled the fan switch again. I'm sorry to say that it has gone to meet Soichiro. Why they couldn't have used a standard issue switch is beyond me. The replacement Honda part and even the after-market ones are expensive ($45 to $100!). The one in my Ford does the same job for $8.

Again, thanks for all the help.
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