09 Kenworth T370 blowing "key switch" fuse

Discussion in 'Kenworth Forum' started by Mach, Oct 11, 2021.

  1. Mach

    Mach Light Load Member

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    Nov 19, 2017
    Knoxville Tennessee
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    So out of the blue, my truck is blowing the "key switch 10 amp" fuse. Started cruising on the highway when I made a down shift to pass a slow truck. The check engine light came on immediately but truck drove fine. Took it about 10 miles and got off at a pilot to stop at the service shop. Roll into the parking lot and the truck immediately dies. No power to the key. Everything else is lit but the key does nothing. Come to find out the key switch fuse blew. Replaced it and all was well.

    Still wanted to see what the check engine light said but they shop computer wasn't working, so I said eff this and left. Go to pull out of the parking lot and as soon as I went for 3rd gear, she died again. Same fuse. Replaced it a again and now parked my self up.

    Off note, I had the starter replaced 2 weeks ago. I check under there and saw that the ground cable was rubbing against the starter pretty good and cutting through the insulation. I shoved a piece of old hose to separate the two thinking I'll fix it later, but now it looks like I'll do it here. I don't know if that could be related at all.

    I'm not sure if the truck will continue to run with that fuse blown at highway speeds but the CEL and the second time the fuse blew both happened when I was giving the beans. Any ideas?

    Mechanic here is useless and has no idea.

    2009 Kenworth t370
    Paccar px8 (Cummins 8.3)
    Eaton 10 speed manual.
     
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  3. circle h

    circle h Light Load Member

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    Oct 22, 2020
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    What do you have hooked to keyed ignition power. Stereo, cb, chargers, etc. If you had an amp meter you might start unhooking items and see if you find something that has become a big draw. You might also check your fuse diagram and see if that fuse feeds a relay. You may have a relay that went bad. 10 amps isn't a lot for keyed power. These are just guesses, but where I would start. I hope you find it quick.
     
  4. Mach

    Mach Light Load Member

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    Nov 19, 2017
    Knoxville Tennessee
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    Thanks for the quick response. I do t have an amp meter, just a basic test light. And as far as what's hook to that fuse, it's all typical factory stuff. Only stuff that turns on is everything on the dash, cb, and HVAC stuff. And I'm trying to find a diagram for this truck but all I can find is t800 and w900 stuff. But I'm still looking
     
  5. circle h

    circle h Light Load Member

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    Oct 22, 2020
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    Did you get it figured out? There is an ignition relay. You could switch it with a relay you aren't currently in need of.
    Screenshot_20211011-173924_Free Adblocker Browser.jpg Screenshot_20211011-173953_Free Adblocker Browser.jpg
     
  6. Mach

    Mach Light Load Member

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    Nov 19, 2017
    Knoxville Tennessee
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    Gave up for the night. I have already switch the relay with a similar one and that did not help. Truck has an ignition relay, ignition fuse (15amp) and the key switch (10amp) Wich is the one that blows. That fuse box in your picture is different from mine. So I wond 20211011_205124.jpg 20211011_205138.jpg er if that's from a older model or not.
     
  7. circle h

    circle h Light Load Member

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    Oct 22, 2020
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    I wish I had more for you. Sucks when they don't work right. I hope you find it. You might look behind the dash for anything that might be grounding outwhen the truck moves. Good luck.
     
  8. Mach

    Mach Light Load Member

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    Nov 19, 2017
    Knoxville Tennessee
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    That's what I'm going to tear Into In the morning. She's old and cranky at times and just needs a little help. What I'm hoping is that check engine light I got before all this may lead me in the right direction. Won't know until the shop I'm stick at fixes there stuff. In the mean time it's ripping the dash apart to see what I can find.
     
  9. Mach

    Mach Light Load Member

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    Nov 19, 2017
    Knoxville Tennessee
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    Update: still having issues but was able to make some progress today in the drive. Spent all morning chasing and jiggeling every single wire on the truck with the truck running to try and get it to pop, never did. The shop got it's computer working and scanned the truck. Two codes one is unrelated and I fixed it. Was the cank case filter being bad. The other was read key switch abs power fault or something like that but gave no details. Now I know the abs does it's checks when you turn the key so I wonder if that is related in some way. Checked all the wires and couldn't find anything odd.

    Eventually I gave up and drove the truck around the lot for a while and all seemed fine. Decided to try my luck out on the road and see if I could make it to my home town Knoxville. Truck drove fine all the way here. Even delt with a lot of stop and go with no issues.

    Decided to park up at the loves west of Knoxville for the night. Get off the freeway and the truck dies right as I get to the traffic light. I frantically take the dash apart and replace the fuse, start the truck and roll on. Pull into the loves and just puttering a long when it dies again. Replace the fuse, park and sit. Truck idles fine with out blowing it.

    100% clueless. Trying to get a wiring diagram from Kenworth to help diagnose it and now haveing my mechanic coming out to meet me tomorrow. Frustrating day this has been lol. Glad the load isn't time sensitive but I hate being late
     
  10. circle h

    circle h Light Load Member

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    Oct 22, 2020
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    Maybe pull the abs fuse see if it does it again? At least most of the day went well.
     
  11. Mach

    Mach Light Load Member

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    Nov 19, 2017
    Knoxville Tennessee
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    I'm actually debating it. I pulled it while sitting here and it doesn't trip the light, but maybe I need to be rolling for it to do such. But that is one of the things I'm going to try tomorrow. Right now I'm just hoping my mechanic and I can dig in and maybe find it. I hate by passing problems like that, but glcant sit forever. Customer will want their steel lol
     
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