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Discussion Starter · #1 ·
I have installed a Linclon Mark VIII. It seems to cool very well but I would like to install a switch to turn it on automatically when the temp starts to get too high. I don't trust myself to ALWAYS remember to switch it on when it needs to be on and I don't want to run it all the time.

What vehicle would have thermostatic switch that would turn the fan on at approx. 195-205 and off at 180-190. I installed a switch of this type (screwed it into the crossover near the temp guage sending unit) that I had lying around, but it apparently is defective as the temp went up to 225 it did not turn the fan on. I don't know what it is out of or what temp it is supposed to operate at. I grounded the wire at the switch and the fan worked so I think the switch I have is definately bad or does not "turn on" until the temp is over 225. In either event I want to find another switch that "turns on" (creates a ground or continuity) no higher than 205 degrees.

Any idea what vehicles might have come with this type of switch? If it is available I would prefer one that "turns on" at 200 degrees.

Thanks, Joel
 

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I put up a post in bench racing about he very same thing. It got side tracted, but has some good info in it.

I should find a solution soon. I'll let you know how that turns out.

BUT, if you find a part that does what you listed. let me know ASAP!

-Mike

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71' 3880# with me. Big Block 402, TH400, 3.73 posi,
13.1sec @ 105 MPH (poor 2.1 sixty foot and rookie tuning)
--will be racing at Chevellebration 2001!--
Picture of me roasting the tires and other guy stuff
Video of me staging (smoke of course)
 

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Discussion Starter · #3 ·
I stopped at Trak Auto today and tried to find a switch. I think the switch I have is from an 85 Olds 98 that I used to have. I asked them to look up that part and it is exactly like the one I tried in the car. It is not marked but their book said 108C. I'm not sure but I think this must be the Celcius temp that the switch "turns on". I ran my car longer today and I was just about to manually activate the fan when it switched on at about 230 degrees. It shut off again at about 220 degrees. I am not certain but I suspect that 108C is approx. 230F. This is way too hot for me.

Trak Auto let me look thru their box of Electric Fan Switches. The one for the 85 Olds 98 was a KEM RF2. It has a 3/8 NPT thread and that is what I drilled and tapped my intake crossover for. I could not find any others with 3/8 NPT threads but I did find one that would thread into the 3/8 NPT hole, it just never got tight like the 3/8 NPT switch does. It was a KEM RF3. The switch is marked 92 87. I think this is the Celcius turn on and turn of temps.

I bought a KEM RF3 and installed it with a lot of Teflon Tape to keep it from leaking(this seemed to work OK) It has an O-Ring but the O-Ring just "squished out" when I tightened it down. It might stay in and work if I put a bevel at the top of the threads in the crossover. I ran the car for a while and the fan switched on at about 192-194 it only ran for a few seconds till the temp got down to 188-190 and shut off. It is very cold, approx. 35 degrees out so I assume it will run much longer when it is warmer out. In my opinion the KEM RF3 will work OK.

I currently have my fan wired (thur a 75 amp relay) directly to the battery. I will be connecting the switch wire to only run in the on or acc. positions. When I shut the car off the fan would run for several minutes before shutting off. I assume this is because the water is not circulating and no matter how cold the water in the radiator gets it does not cool off the water in the crossover.

If anyone finds a better switch(especially one with 3/8 NPT threads), please let me know. I would also prefer one with a bigger temperature gap between the turn on and turn off temps so that the fan will not cycle on and off so often.

Thanks, Joel

PS. I don't know what vehicle/s the KEM RF3 is supposed to fit. Does anyone know? What type/size of threads does it have?
 

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I'll stop by auto zone friday and see what I turn up.
 

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WE are getting closer yet.

STopped by autozone and looked at what they had to offer. Desk people where to helpfull. I ended up buying 2 units. No temp numbers, just trial and error. Niether unit swtiched ON while held in boilng water (210*F) And if they do switch above that, woopy, I DON'T WANT IT.

The summit piece is looking more apelaing by the day. In case you don't know about it yet. Jegs/summit both sell them. They are listed in the "ECU upgrades" section. They appear to be the exact same design as what you and I are testing. Just a screw in 3/8" fitting copper piece with a black top and single prong in the middle. They are listed as "ON @ 200, off @ 185" they have one lesser temp unit also. only bummer is, price is $44 plus shipping.

I am stopping by the GM dealership Friday. Will maybe having some more answers by friday evening.

---ALSO---
I am wondering wether or not these are actualyl switches. i.e does the unit complete a "swtich to ground" when 'said' tempature is reached? OR, does the computer moniter this aparent voltage drop across this piece in acordance with the whole "REsistance is lowered as heat rises" principle.

-damn it-
I'm gonna end up paying the $50, cuz I design some home-made unit. My last resort is a small IC that outputs a voltage proportional to the chips tempature. only bummer is, the darn thing increments in milli volts and is ment for industry application. i.e. 180-210 degrees might very well be a fart in the wind to this guy.


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71' 3880# with me. Big Block 402, TH400, 3.73 posi,
13.1sec @ 105 MPH (poor 2.1 sixty foot and rookie tuning)
--will be racing at Chevellebration 2001!--
Picture of me roasting the tires and other guy stuff
Video of me staging (smoke of course)
 

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Discussion Starter · #6 ·
The RF3 switch that I bought has two terminals that are normally open. Closes when temp goes over 194?? I connected one side to ground and one side to fan relay but you could also use it to complete the +12V feed to the relay if you wanted to.

If you call/E-Mail Summit, they may be able to tell you how their "switch" works. If you get one, or find out how they work, please let me know.

Thanks, Joel
 

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Joel,
Hypertech, the guys that make the performance computer chips, have a fan switch that keeps the temp at around 180. I dont remember the exact temp, but I have the info at the shop.
Hope this helps,

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100
 

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Utto. Me thinks they work like this:

As they heat up the resistance scene buy the "top post" changes and so does the voltage at that point. Maybe the ECU actually monitors this voltage and turn on a relay accordingly??

I just tested mine using a multi meter set on the "check diode and beep" function. I'm about to get back on the lab suit and see what is REALLY happening with this do-hickies.
 

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Discussion Starter · #9 ·
Bill,
I am running a 180 thermostat so I think a switch that activates at 200 and shuts off at 185 would be ideal.

Does Jet, or anyone else, make one with that operating range with 3/8 NPT threads.

I saw the Jet Fan Switches in the Summit Catalog (page 103) that I just got today. It list them for 3 different cars so I assume the mounting arrangement is different on each switch. One of them may be correct but I don't know which one to order.

On the same page Summit lists "Painless Electric Fan Relays", one of which is rated at 200/185. I don't need the relays but they list "replacement thermostat". I am not sure but I suspect the "replacement thermostat" is actually the type of switch I am looking for.

Both of the "switches" (Jet & Painless)are shown in photos and they look like the correct design and thread type for my car. I would like to confirm before ordering one.

I would prefer an OEM switch if one is available. It would probably be cheaper and it would be easier to get a replacement if I ever need one.

Thanks, Joel
 

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The light at the end of the tunnel is looking more and more like a train.


I just got through doing a nother test on my "thermostatic sending units"

By just suspending them in 210* of water they don't do jack. However, if I press the base against the bottom of the pan, (still keeping the top black piece out of water) the red hot stove coils heat through the pan and give me a tempature unkown, but I say aroun 230*. Something happened!

The "fatter base" unit showed a resistance very quickly after being applied to the bottom of the pan. 5 seconds after touching the meter read 25 Mega Ohms. 5 seconds later I was down to 3.3 Mega Ohms. Wouldn't go any further.

The second unit didn't do anything after 5 seconds, but after 10 seconds showed me 19 Mega Ohms. So it is a "higher temp application"

REsults: hell, I don't know? What can I do with 3 mega ohms? With a 12 volt source that will only sink 0.4 micro Amps. That can't be near enough current to cause our relays to latch! Maybe the late model ECU cars monitor this unit with a "current sense" device and 0.4uAmpere is enough for it to trigure and go do something.

--I'm gonna figure this crap out!

JOEL. I think what you witnessed is the relay getting just enough current to latch itself. MAybe meaning that these switches (that are really tempature dependent resistors) do 'operate' at a lower tempature, but for the way we are using them, the design engineers would laugh their asses off.
So the above $44 dollar item might not work either. By god, I just need to design something and have CopperTop market it


I just read you last post. Let me know if you find out anything on that 'painless wireing' setup. And what the hell is that two terminal little metal can in the picture?!?!?

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71' 3880# with me. Big Block 402, TH400, 3.73 posi,
13.1sec @ 105 MPH (poor 2.1 sixty foot and rookie tuning)
--will be racing at Chevellebration 2001!--
Picture of me roasting the tires and other guy stuff
Video of me staging (smoke of course)

[This message has been edited by BB_Mike (edited 04-19-2001).]
 

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I just got off the phone with a tech guy at Painless wiring. What the sell (and you can get it through summit) is an item similar to what we dealing with. Their piece screws into the 3/8" fitting and can be used as a switch and NOT something that the ECU monitors. It will come on at 200* and off at 185*.

Summit part number is PRF-30110 price is $32.95

I'll check and see if GM can do them one better and beat that price. If not we'll just have to spend the $40 to get one to our door.


-the tech guy said the unit creates a "short to ground" when it reaches 200* and maintains this short untillthe unit cools below 185*.
 

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Mike,

Check at Bill Heard for a 80's model Corvette electric fan switch. My 81's fan is a +12V switched unit. I don't know the turn on/off characteristics, but it does turn on and stay on for awhile bringing the temp down before shutting off. It failed one time and I had to jumper the plug to run my fan until I could change it out.

Don't try to re-engineer the world when temp range switches already exist. I know it's fun to put into practice what you have learned, but it is also more time consuming sometimes.


Brian
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by 65elcamino:
Mike,


Don't try to re-engineer the world when temp range switches already exist. I know it's fun to put into practice what you have learned, but it is also more time consuming sometimes.


Brian
<HR></BLOCKQUOTE>

AMEN!

Bummer is the local GM guys don't know the above mentiones characteristics. So I basically buy an assortment and then go home and test them out. The design idea is if all else fails.
 

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Went by the GM dealer today and that was a big ol' waist of gas! NOt only could they not tell me what tempature the various units swtiched on/off at, but he said there is no return on any electrical stuff purchased there. Hell, autozone took back the ones I bought that didn't work like I wanted them to. I'm about fed up with my GM parts people.

FINAL ANSWER: I'm about to place an order for the "replacement thermostat" piece sold by Performance Wiring. Thier tech guy told me that is what I need and it will work like it needs to (driving the realy directly). If you want to wait for my trial run of it just let me know.

Should get the part in tuedsay. weather pending, I'll have some results for you by thursday.
 

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Oh yeah. The above mentioned GM piece cost $36!!! No crap. So I am paying only $2 more and I know EXACTLY what the switching tempatures are.
 

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Mike,
I am almost certain that all of the GM switches turn the fan on at approx 230 degrees. I have never heard of one that works at any lower temperature. The newer models do use a variable sensor that tells the ecm what temp the motor is at and then the ecm turns on the fan....but you cannot use that type of sensor by itself.
The Hypertech 160 degree switch is part number 4026. I do not have the part number for the 180.
Hope this helps,

------------------
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100
 

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There are different types of (temp switches) that were installed in GM cars. Older cars without electric fans had either a temp "switch" that activated a temp light by switching to ground, or a temperature sending unit which would vary in resistance based on temperature. Newer computer controlled cars typically use a sending unit that varies in resistance so that the computer can monitor the temperature and turn the fan on and off accordingly, also would give the signal for a digital dash temp gauge. Some aftermarket sending units that claim to lower fan on-off temps, do this by fooling the computer into thinking the motor is hotter than it actually is. There are many aftermarket fan "switches" available, check with the electric fans manufacturers. It should'nt be a problem to get what you need from them!
 

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Hi all!

A Polaris head cylinder temp switch off of a 97-05 sportsman 400 closes at 205 deg F.

This will turn on a relay or fan. It is norm open but at 205 deg F it closes and grounds the wire to engine.

They go for around $42.00 up.

Mike :beers:
 
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