looking for temp/ fan switches for two speed fan

[mc1984ss]

I am getting ready to put a new replacement Mark VIII fan in my very long slow project. I am going to use the Hollister road company wire harness/ relay kit. ( http://www.hollisterroad.com/proddet...?prod=MarkVIII ) If you are not familiar with it this wire harness operates the high and low speeds on the fan with two separate temp/ fan switches. The low one turns on at 185 degrees and the high turns on at 200 degrees. The sensors they sell are 3/8 npt. I was planning on putting the two temp sensors in the radiator tank where I have two bungs that I thought would be perfect for this. I am looking for the two fan switches/ senders of the same temp. on and off but 1/4" npt. I could even use a 1/8" npt switch. Does anyone know where I could possibly find this? Thank you in advance!!!

[H2Ogbodies]

The Mark VIII fans are not 2-speed. They are single speed and with the replacements being Chinese, I doubt they are as stout as OEM Motorcraft fans. I know Hollister lists it as a 2-speed Mark VIII kit but the fans don't operate as a 2-speed so I'd be curious how they would expect their kit to work with one.

Now, the T-Bird RF24 fans ARE dual speed and would work with their kit...but, I would suggest keeping with engine installed 3/8 NPT temp switches either in the t-stat housing or intake.

[Justin@EntropyRad]

You will need a fan with a dual coil to operate it at two speeds. To bring the wiring up to pro-touring specs, you might want to look into sealing up those relays with epoxy to keep moisture out.

[H2Ogbodies]

http://www.hotrod.com/how-to/engine/...radiator-fans/

This is old article but they talk about using a Mark VIII fan all throughout the article as well as mention all the 2-speed controllers on the market (at that time anyway...) but their "mockup" shows a 2-speed T-Bird RF24 as evidenced by the black fan plug. Mark VIII's have a white plug. Also, all versions of the fan plug have 3 terminals-its in the wiring itself about 12" in that the Mark VIII's have the center wire cut-that would normally be the low speed output. But, since the Mark VIII fans are single speed by design, they have 2-actual wires to the fan -high speed and ground. Lincoln used a type of VSC for the fan using fixed transistors to act as a variable speed control unit and it not easily adaptable. The article is a little misleading so do some research on the Mark VIII fans if buying used.

[thoroco]

The use of Mark VIII fan in our articles and sales text is due to the internet lore that a Mark VIII fan is two speed and sold on eBay as that. As much as we try to get the message out that a true Mark VIII was never a two speed the T bird fan was used as a replacement for the M8 fan in an M8 car because of the cost difference, this is why you see "I got it from a M8". We try to dissuade people from the M8 two speed notion but it remains today as strong as ever. The next question is what the difference in speed. Answer is not much, It looks different because it was run by a pwm unit and it was in a very expensive car and Ford didn't want the fan noise to be heard so they changed the blade pitch not the CFM. It does not blow 4000 -5000 cfm, its actually more like 3200 MAX on high, about the same as a dual spal. Yes I do have the testing to back this up. Test data

We have been making and selling M8/T bird/Taurus relay kits since 2006 and have yet to see an actual M8 two speed and I get calls every day on the elusive M8 two speed. Unfortunately we don't have editorial control over CarCraft and Hot Rod magazine and they did get some points wrong but the general gist of what we do and how it works is correct. Seeing two or 3 wires is also deceiving because I have seen 3 wires on certain year M8 fans and two wire on others, the only real way to tell is test the fan, power it up and if it changes speed by at least 800 rpm its a two speed, it you can't tell a speed difference then its a single. True M8 fans come with white plugs and black plugs, 2 wire and 3 wire all are dimensionally the same as a T Bird/Cougar two speed for a 4.6 V8.

[H2Ogbodies]

I'm sure a lot of the confusion even before 2006 was that the two fans do "look" similar....even though they differ in activation. However, since the OEM Motorcraft fans are no longer available, I don't worry too much about it anymore-the offshore replacement fans aren't an equal to the Siemens design anyway.

I've talked with a Siemens rep who worked on the design of their fan motors for Ford who wanted the most stout motor to quote "run 24 hours/day for 10 years if need be" since they would incorporate them in their high end Lincolns and police duty CVs. Obviously its a little much to ask out of a fan motor but nevertheless, its a big reason why they are still a popular fan-STOUT even as a used/high mileage fan!

[ixfn]

I have had great success with a BMW temp sensor (3 terminal, 2 speed), Volvo fan control relay (2 speed), with M8 and T-Bird fan assemblies. The Volvo relay handles a lot of current and is controlled by low current ground signals which the BMW unit outputs, and is easy to add override signal switches. The BMW unit is metric, so I've just drilled and tapped brass fittings to adapt them. It also works progressively (off, low, high, low, off), which helps avoid current spike. I can get application, part numbers, and pictures in a few.

[H2Ogbodies]

Yep-I too have been using them as well. I like to use a thermostat spacer and drill/tap it for the 14mm x 1.50 thread pitch. Looks more factory than using a wayyyy overpriced bushing adapter. The Volvo relay is a stout unit to be sure....however, when it comes to high powered OEM fans I still prefer my 3-speed approach. On average its about $50-60 to install a BMW dual temp sensor without the spacer....but IMO its worth it because it does look good!

[hessdawg]

My mark VIII is a true dual speed, I pulled it from a black Lincoln. I also took the BMW sensor ground it down and retapped it with 1/4 NPT and in stalled it in radiator drain

[thoroco]

The BMW switch needs to be on the radiator like you have it, They don't seem to work well at the motor. Send me a picture of the plug and blades of your fan to [email protected] , most of the M8 two speeds were actually a Tbrid fan used as replacements because they were $200 cheaper and looked and fit the same. i'd like to see how it compares to a Tbrid fan.

The new control we have on the drawing board will run a Taurus or M8 two speed with one sensor, adjustable temps, ac , and doesn't use relays. No drilling tapping needed, no pipe ports needed, The sensor slips between the hose and water neck of the radiator and picks up that temp, Also has a soft-start so no spikes at all to worry about.

[hessdawg]

I got 2 from pick and pull
One was a single speed
One was 2 speed