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  1. #11


    The temp switch came in last week, though I haven't gotten to make any progress yet because I'm still waiting on relays. I ordered a couple Bosch 75 amp relays like this:

    They're supposedly rated for constant duty at 75 amps. I need 2 of them to run the fan in the 2-speed setup I intend to run, and the place where I ordered mine just happens to sell them in groups of 4 for right around $10 each. So, I'll have a spare or two to carry with me in case one goes out, but I hope that doesn't happen.

    This weekend I needed the Suburban and since I didn't have the project done, I converted it back to the mechanical fan. It took 30-45 minutes to complete and if I had to, I should be able to find the actual fan and fan clutch at any auto parts store for a reasonable price. I won't have the fan shroud, but it should be enough to get me home should the electric fan go out and I'm unable to find parts to fix it. So that's definitely a plus in my book.

    I hope to have the relays in hand this week, though the earliest I can try to get back on this project is next Sunday. Hopefully I can get this project done. In the meantime, I have what I suspect is an ignition problem to sort out.

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 265K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half

    There are 10 kinds of people, those who understand binary, and those who dont...

    Remember kids, the only difference between screwing around and science is writing it down- Adam Savage

  2. #12


    I was thinking today about this project and was searching for the upper radiator hose I need to get to fit the water neck I bought, when I stumbled across another solution that may be more optimal for me. I think I may use a radiator hose adapter like this:

    Using an adapter like this will permit me to have more free-form placement of the temperature switch, have it electrically isolated from the block in case of shorts, and allow me to use the cheap and easy to find stock radiator hose. The adapter is pricy at around $45, but I think it would be an optimal choice for quick and easy roadside repairs where I might not be able to find esoteric parts.

    What say ya'll to my new plan?

  3. #13


    I have the relays in hand now, but the project got stalled due to a lack of funds and breaking a connector for the coil pickup in the distributor. I'm hoping to hit this project again hard in the next couple weeks. But not until I replace the distributor and get the truck running again.

    I have now firmly decided that I will go the adapter route and not change water necks. Having to source the proper radiator hose was proving far too hard. Any ideas what size adapter I need to put my sensor in? I need to measure the hose where I plan to put the adapter then subtract the thickness of the wall of the hose.

  4. #14


    watching the thread as an efan upgrade is something I have considered doing eventually. I like the idea of the radiator hose adapter.
    2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
    1960 Land Rover Series II 88
    2001 Pontiac Sunfire
    2013 Toyota Avalon Limited (Wife's Car)
    NRA Life Member

  5. #15


    The distributor has been replaced, so that issue is resolved. All I have left in terms of parts to get are the sensor adapter and wire to complete the job. I'm still a couple weeks off though because of my car needing to go to the shop for work.

    During the wait, my factory service manuals came in. I was perusing through the A/C section to try to get some info and plan out rebuilding the A/C system from scratch. While reading, I solved an issue I foresaw with my plans for the e-fan. Originally I was planning to run the fan on low normally, but when the A/C clutch was locked in, kick the fan up to high speed to help the A/C out. However, with the compressor cycling in and out quite frequently, I was worried about killing the fan or the relays. The manual gave me the answer: pull the feed for the A/C override from before the low pressure switch on the accumulator. What controls the clutch pulling in and out is the low pressure switch, and the feed to the switch is always hot whenever the mode switch in the cab is in an A/C mode. So, the fan will run high whenever I have the A/C lever in an A/C mode. Much longer on-time for the fan in high, and more happiness by me being cool in the cab. A bonus is that getting to that power feed is easier than getting the clutch feed I was originally planning.

  6. #16


    I just ordered the Mishimoto MMWHS-38-BK temperature sender adapter to go in my upper radiator hose. Hopefully I chose the correct diameter of adapter. Provided everything goes right, I should be putting this all together next weekend.

  7. #17


    These are suppose to be some good thermal switchs..

    i bought a couple of them for my transmission cooler lines on my Samurai so it will run the fan on the Trans cooler. Havent tried them for reliability yet tho.
    2000 ECSB Silverado 2WD
    LQ4 with Isky 215 Turbo Cam
    4L80E KB Racing S475 Turbo Kit

  8. #18


    I'm sorry this project's gotten stalled, but between life and acquiring parts and working out strategies and methods to make it work, it's gotten put off. I'm hoping to get back on this soon to get it done.

    My initial plans were to run this in a 2-speed setup, but from the looks of it, I got the 1-speed model fan. No big deal, I just can't modulate speed based on need. That will make the wiring easier as it will now just be 1 relay with a couple diodes and 2 feeds: one from the temp switch in the upper radiator hose and the other from the A/C compressor power feed. However, this will most likely make the fan run non-stop when the truck is on since the A/C will virtually always be on in all but the winter. Any thoughts on that?
    Last edited by Crawdaddy; 09-26-2013 at 10:22 AM.

  9. #19


    I think that the fan running when the Ac compressor is on is what you want. My 2005 yukon xl came with twin factory installed e fans. When the AC is turned on both run on high. When I shut the ac off either one or both will stop depending on my coolant temp

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  10. #20


    I've noticed that in general, it seems that for electric fans, the ground seems to usually be the side that's switched with the relay. Why is that? I was planning on switching the positive, but I could just just as easily switch the ground. Just wondering what the logic was.

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