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  1. #1
    DHG FTW! ninety5fiveoh's Avatar
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    Keep blowing 50 amp fan fuses! HELP PLEASE!

    When I put my blower together and got it tuned, a few days later the 50amp fan fuse blew. I traced the problem, replaced the 50 amp fuse and it has been good for over 2 months. The last week my a/c has been blowing non cold air occasionally, and today I was sitting on the highway in traffic and the temp gauge went to about 235-240. I shut it down and let it cool, checked the fuse and sure enough it was blown. I replaced the fuse, fired it up, the fan tried to spin and blew the fuse again.

    I honestly don't know where to start, I've done a lot of searching but haven't found really what I'm looking for. Suggestions would be awesome, thanks!


    2001 DHG Bullitt - #4113
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  2. #2
    M112'd Roush x2 LilRoush's Avatar
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    Check the 3 pin plug going into the radiator fan motor. These cars like to melt them... and they ground out. Causes the fan to either blow the fuse to kills the fan motor itself (which can also lead to popping the fuse). Based on your description, I'd guess that's what is going on. When mine went, I just hardwired it myself instead of buying another connector.
    1998 Roush: M112 - Cobra short block - T56 - 1 of 1 made.
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  3. #3
    DHG FTW! ninety5fiveoh's Avatar
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    I checked that this morning and it looks perfectly fine. I also jumpered the motor and it seems as if both low and high speed work ok, but I spoke with Kevin my tuner today and he said the fan is probably going bad which would create more resistance on the circuit and blow the fuse. Makes sense to me, I'm probably going to just replace the fan and the fan resistor to rule those out. Wiring also looks fine. Not sure what's next!

  4. #4
    M112'd Roush x2 LilRoush's Avatar
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    Seems like a smart step. The fan assemblies are easy to swap out, takes less than 15 minutes.

  5. #5
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    You should be doing an ohms check on the motor not voltage check.

  6. #6
    DHG FTW! ninety5fiveoh's Avatar
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    Thanks fellas, I'll report back tomorrow with progress once I get the fan.

  7. #7
    DHG FTW! ninety5fiveoh's Avatar
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    UPDATE:

    I swapped the fan, low speed resistor, and fuse out. It ran perfectly for the last 3 weeks, sitting in traffic on 90 degree days, etc. Now today randomly the fans quit and the fuse IS NOT BLOWN! Also, with the a/c on there is a SLIGHT whirring noise coming from the engine bay.

    I am getting sick of this issue and throwing money into the car to try and fix this. Does anyone else have any more suggestions?

  8. #8
    M112'd Roush x2 LilRoush's Avatar
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    Did you do the wiring connector to the fan as well?

  9. #9
    DHG FTW! ninety5fiveoh's Avatar
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    Quote Originally Posted by LilRoush View Post
    Did you do the wiring connector to the fan as well?
    As in replace it, or test it. I haven't done either. Last night I was driving home from work and the fans were working perfectly fine. I also drove 13 miles to my buddy's house this morning to detail our cars and it worked fine. I brought my multimeter with me but the blower just gets too damn hot to reach under and I kept burning myself reaching for the clip. BUT, on my way home, the fans didn't work. It ALMOST boiled over, I got it home just in time. I checked the fuse, and it is NOT blown. I've also noticed that the whirring noise I mentioned before, ONLY happens when the fans aren't working. I notice it as I run through the gears, and it gets progressively louder as rpms climb. I'm almost wondering if it has something to do with the air conditioning system.

    Thoughts?
    Last edited by ninety5fiveoh; 09-01-2012 at 02:50 PM.

  10. #10
    DHG FTW! ninety5fiveoh's Avatar
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    SUNDAY UPDATE:

    OK, so let me outline where I am currently at to see if this helps. I also made a little headway on diagnosis:

    - I start the car cold, fans are obviously not on.
    - I turn the a/c on MAX (car still cold), and the fan comes on as it should.
    - I shut the a/c off, fan shuts off.
    - With the a/c off, car still cold, I unplug the coolant temp sensor on the intake manifold, fan turns on.
    - I plug the coolant temp sensor back in, fans shut off.

    ALL IS NORMAL AT THIS POINT.

    - Wait for car to get to ~188 deg where the tune calls for the low speed fan to come on, which is DOES.
    - Low speed fan runs fine until 194 deg where the tune calls for the high speed fan to come on which is DOES NOT and the fan shuts off completely.
    - At this point I checked the 50 amp fuse in the main engine fuse box and it is NOT blown.

    LET THE CAR COOL FOR 5 MINUTES.

    - Fired the car back up at ~188 deg where the low speed fan should come on which it DOES.
    - 30 seconds later when the car gets to 194 deg when high speed is supposed to come on, it does NOT and the fan shuts off completely.
    - At this point, turning on the a/c on max does NOT turn the fan on, nor does unplugging the coolant temp sensor.

    LS1KILR mentioned the a/c compressor might be going south so I tested that as well with the car COLD.

    - With the car running, I turned the a/c on max, and unplugged the sensor mounted on the a/c line directly underneath my powerpipe. The compressor kicked off. I plugged the sensor back in and audibly heard the compressor kick back on.
    -With the sensor plugged in, I also jiggled it back and forth, up and down as much as I could to see if there was any sort of continuity issue with that plug which there was NOT.

    At this point, from my testing, clearly the wiring to the fans is ok because low speed works all the time, and high speed HAS worked for the last 2 weeks, then only worked intermittently over the last 2 days.
    THOUGHTS?! THANKS!!
    Last edited by ninety5fiveoh; 09-02-2012 at 03:03 PM.

  11. #11
    DHG FTW! ninety5fiveoh's Avatar
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    I just checked the ground wire going to the fan, because from what I have read, both the a/c high pressure switch and the fan run off the same ground. Resistance on 200ohm setting on my multimeter was between 15 and 17 with the fan working.

    I tested this by turning the car on COLD, turning on the a/c to verify low speed fan was working, unplugged fan clip, and tested resistance on the ground wire.

    Even though resistance is high (Haynes manual says it shouldn't be higher than 5), I don't understand why the low speed fan would still work since both low and high speed run off the same ground wire.

    Tomorrow I will test both power lines for low and high speed fans. It is now raining...FML! I want this car fixed!!

  12. #12
    DHG FTW! ninety5fiveoh's Avatar
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    Now its throwing PO118 code - Engine Coolant Temperature sensor. I figured, shit this controls the fans as well, so I replaced it. No dice, still have a CEL.

    EDIT: Went for a rip to blow off a little steam, and when I came back, the high speed fans were working with the a/c on and the car was at around 200 deg. I shut it off, turned the a/c off, turned it back on, the fans were still working and the CEL was gone. Since I changed the ECT sensor, I had cycled the ignition about 5-6 times. Would that have cleared the code in the car? The factory temp gauge works fine, FWIW.

    NOW, this has happened before with the fans working then not working the next day, but maybe the ECT sensor fixed it. Who knows, I hate electrical diagnostics!!!
    Last edited by ninety5fiveoh; 09-03-2012 at 01:16 PM.

  13. #13
    Crazy SVT Poster gregor185's Avatar
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    Electrical problems are the worst..did u clear the Ck engine light after u put the sensor in? Just replacing the part wont just shut off the light


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  14. #14
    DHG FTW! ninety5fiveoh's Avatar
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    Quote Originally Posted by gregor185 View Post
    Electrical problems are the worst..did u clear the Ck engine light after u put the sensor in? Just replacing the part wont just shut off the light
    I was wondering that. The light actually went out on its own after the ignition had been cycled a few times. Cars are weird.

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