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  1. #1

    Join Date
    Jul 2003
    Posts
    15
    Location
    Earlysville VA 22936
    Tractor
    POWERTRAC PT425

    Default Added an extra cooling Fan

    I wanted to share a modification that I have made to my PT425. The initial reason I had for adding an extra cooling fan is an unseated valve and bent push rods. The earlier PT425's have the front of the Kohler engine down in the box at the front. This location on mine wasn't able to pull enough fresh air through the engine. The side benefit that I have enjoyed has been the icing on the cake for this mod. With the extra fan blowing down into the box, the positive air pressure keeps the grass clippings from being sucked into the engine box area. I haven't had to clean the front of the engine off after mowing.

    Now for the details. First I ordered another fan. I went ahead and used the same SPAL fan that is on the oil cooler. It draws around 6 amps. I had some concern about the alternator being a 15 amp source. After talking to the small engine shop whom I had replace the valve seat. They were of the opinion that the alternators almost always supply more current than advertised.

    Next I had to build a box to mount the fan in. There was not enough space to mount the fan flat. I cut a 6" x 11" hole in the top of the engine compartment cover. Mounted the fan and box upright on top of the cutout.

    I tapped the wires for the oil cooler fan before the temperature switch.

    Finally I used flashing to close off the front of the engine compartment cover and 10" back on each side. Under the cover I added a flashing panel extending from the top down to the top of the air filter cover. This had the effect of channeling the air from the fan down to the front of the engine. Activating the fan I could feel airflow coming out the back of the PT425 near the bottom

    The one drawback that I have run into so far is that when the oil is hot and both fans are running, there is barely enough amperage to crank the engine. I haven't decided whether to change the battery to one with a larger cold crank capacity or simply add a normally closed pushbutton switch to the circuit to act as a temporary fan kill switch for cranking.

    Attached Images Attached Images

  2. #2

    Join Date
    Jul 2003
    Posts
    15
    Location
    Earlysville VA 22936
    Tractor
    POWERTRAC PT425

    Default Re: Added an extra cooling Fan

    Hopefully this post will show a pic under the cover.
    Attached Images Attached Images

  3. #3
    Elite Member BobRip's Avatar
    Join Date
    Sep 2004
    Posts
    4,329
    Location
    Powhatan Va.
    Tractor
    2000 Power Trac 422

    Default Re: Added an extra cooling Fan

    The one drawback that I have run into so far is that when the oil is hot and both fans are running, there is barely enough amperage to crank the engine. I haven't decided whether to change the battery to one with a larger cold crank capacity or simply add a normally closed pushbutton switch to the circuit to act as a temporary fan kill switch for cranking.


    Nice looking modification.
    I am concerned that you are discharging the battery while running both fans. The alternator output is only 15 amps if the engine is running at full speed (3600 RPM). While cranking an additional load of 12 amps does not seem like much unless the starter is not getting enough voltage to engage, the push button seems like a good idea, a relay that is engaged with the starter and opens the fan power would be automatic. Does it crank slow or just not engage the starter. If you have a multimeter check the battery voltage with both fans running and the engine at full speed. You must have at least 12.6 volts to keep from running the battery down, and 14 volts would be much better. A larger battery will not help for long if it is being discharged while using the tractor. Still with a larger battery, you could trickle charge the battery between uses and probably get by. Better to run a battery down than overheat an engine.

    Bob Rip

  4. #4

    Join Date
    Jul 2003
    Posts
    15
    Location
    Earlysville VA 22936
    Tractor
    POWERTRAC PT425

    Default Re: Added an extra cooling Fan

    I am one of those operators that runs the engine at full throttle whenever I am using the PT. I have put 20 hours on since the modification and haven't run the battery down yet. The sympton with a warm engine is the dreaded click - click then the engine starts turning over. This occurred the first day with the modification. When first starting the fans actually draw more than 6 amps until the fans are turning. I like the relay off the starter idea. This seems to be the slickest solution. The trickle charger was my backup plan. [img]/forums/images/graemlins/smile.gif[/img] [img]/forums/images/graemlins/tongue.gif[/img] [img]/forums/images/graemlins/ooo.gif[/img]

  5. #5

    Join Date
    May 2004
    Posts
    247
    Location
    Washington - West Cascades
    Tractor
    PT-422

    Default Re: Added an extra cooling Fan

    Nice looking mod!

  6. #6
    Platinum Member tmarks11's Avatar
    Join Date
    May 2005
    Posts
    716
    Location
    Port Orchard, WA
    Tractor
    Power Trac 422 (2005)

    Default Re: Added an extra cooling Fan

    where did you order the SPAL fan from?

    I have been thinking that maybe another fan mounted on the right hand side of the canopy, so that it blows across the exhaust manifold might be worthwhile. It would circulate air acros what is probably the hottest spot in the engine compartment.

  7. #7
    Elite Member BobRip's Avatar
    Join Date
    Sep 2004
    Posts
    4,329
    Location
    Powhatan Va.
    Tractor
    2000 Power Trac 422

    Default Re: Added an extra cooling Fan

    If you turned the key to on and let the fans get upto speed the current would drop and then it might start better. This is all a little too marginal for me, the relay solves it all.

    Thanks for this concept and pictures.

    Bob Rip

  8. #8
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
    Posts
    18,288
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Added an extra cooling Fan

    A good volt meter will help solve some of your problems. Hook it up to the battery and turn switch to on, observe the voltage. Turn the key to start position, and observe the voltage. With engine running, you should see the charging voltage.

    You could also add another battery to the circuit, with a one way diode so that the fans run only off the second battery. The engine would charge the second battery, but it would only be used for the fans.


    There might also be a larger alternator for that engine.

  9. #9

    Join Date
    Jul 2003
    Posts
    15
    Location
    Earlysville VA 22936
    Tractor
    POWERTRAC PT425

    Default Re: Added an extra cooling Fan

    <font color="red"> </font> where did you order the SPAL fan from?

    <font color="black"> </font> The fan is a SPAL VA11-AP8/C-29A. Ordered cost $62.00 + shipping. This is the pull version. Hindsight says that I should have used a push version. You want to find a Hot Rod shop close to reduce the shipping.

  10. #10
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
    Posts
    18,288
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Added an extra cooling Fan

    You should be able to reverse the wires to make it run the other way.

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