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Thread: 1998 Freightliner FLD120 ***PROBLEMS***

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    Default 1998 Freightliner FLD120 ***PROBLEMS***

    Does anyone have any suggestions on why my fan won't shut off....???

    It cools my engine right down to less than a 100 F

    Thx Mike

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  3. #2
    Uturn2001 is offline Senior Board Member
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    Is this a new problem?

    If it has "always" done this since you have had the truck check to see if someone has run a jumper wire at the fan.

    If it is something "new" then check the switch on the dash.

    If that isn't it then it is probably a bad temp sensor.
    Finding the right trucking company is like finding the right person to marry. I really comes down to finding one whose BS you can put up with and who can put up wih yours.

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    allan5oh is offline Senior Board Member
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    "down" to 100? There's no way your engine should be able to cool itself off that much.

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    Malaki86 is offline Senior Board Member
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    "down" to 100? There's no way your engine should be able to cool itself off that much.
    It could if the thermostat is bad as well. Nothing like a bad thermostat to make a long drive on a cold day/night a living hell.

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    btinc is offline Senior Board Member
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    Most fans are controlled by air to turn them on and off. There is a internal gasket that could be bad. There are fan hub kits to fix this problem, just make sure the hub is put back on straight. The kit is in the 200 range and a new one is in the 500-600 ranges. That bad gasket is the most common problem with a easy fix.


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    I live in calgary alberta...the temp outside right now is -25 C. I tried changing the the EDM under the dash as well as changed the sulanoid for the fan still nothing...So i took it one step futher, on the EDM there is a wire labelled (Fan Control). I spliced into it and hooked a two way switch up to the wire and grounded it. works great but still not fixed anymore ideas???

    thx for the idead btinc

  8. #7
    stranger is offline Member
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    As for the engine temp. If you have a Detroit, the thermostats go bad on a regular basis. Change both, and use new seals.

    The fan is probably a Horton. The Horton fan switch go bad on a regular basis also. It is either screwed into the fan shaft behind the pulley, and if not, follow the air line back until you come to a connector that has an electrical wire to it.


    This is the Horton fan control. Change it if you haven't. I have seen them go bad at the rate of two a year, while some will last for several years.

  9. #8
    mrpersons is offline Member
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    I don't know about your fan clutch, but mine works by applying air to the clutch to disengage the fan. With the engine off and air up, remove the air line to the cluch, apply 12v to the solinoid by use of a jumper. If that works, try using the trucks 12v, key on, not running. If that works okay, reattach the air, apply 12v, (do not start engine), and smack the fan clutch hub with a hammer, and see if the fan rotates freely. If air goes where it supposed to, you're good to the clutch. If it won't break loose, rebuild or replace the clutch assy.

    You get all that??? (mine likes to stick if it's been sitting for awhile)

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    I did mr pearsons thx. Ive tried everything except change the thermostat and rewire the whole thing. If its not the thermostat m guessing its grounding out somewere. For now, the switch i put in works great but ill have to fix it b4 summer as its not working right. Im gonna try the thermostat this weekend and see if that does it. I dont think its the fan hub because i can't hear any leaks with the truck off. I had it in the shop this week and it cost me 500 bucks only to find out it still wasn't fixed.. Thx for all the ideas, pls keep em' comin

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    Thx for the help people

  12. #11
    stranger is offline Member
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    The fan solenoid has a normally on and a normally off setting. Look at the instructions that came with the switch.

    There should be two places that you can hook up the inlet air line, and one exit line to the clutch. It may be hooked up backwards, and may have been that way when you bought the truck.

    The correct setup in most applications is: when the key switch is on, the fan will rotate freely, and then will engage with the switch turned off. If your fan turns freely with the switch off and the air built up, then the fan switch is hooked up backwards.

    Some switches change the on off settings by the electrical plug, but most just have a total of three places to hook up air lines, and you use the correct one for your application. They are easy to get backwards.

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    roadranger is offline Board Regular
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    My fan clutch on my 1995 FLD120 is a Kysor and is presently stuck on like yours might be. With the hood open turn on the key but don't start the engine aand see if you can hear an air leak in the clutch like mine. If not, now turn the fan by hand with the key still on - it should turn. If not it is stuck on. I bought a rebuild kit from Freightliner for $115 but haven't put it on yet.

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    GMAN's Avatar
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    I would guess it is the fan clutch. That happened to me once with a Detroit. I nearly froze until I could get it fixed. :? There is nothing like being in a foot or so of snow and having your heater blowing out ice cubes. :shock:

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    I once drove home from Baltimore with no heat,the temp was 38 when I left and sunny,kept cab warm until the sun went down for the last 2 hours,basically wrapped myself up in a sleeoing bag........ah the memories

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    I have tried changing the sulinoid, i checked to make sure it was hooked up right by turning the key on, everything seems to be working fine. Ive come to the concultion that its a wiring problem. Im just gonna rewire the whole thing. Thx for the tips guys

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    GMAN's Avatar
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    Have you checked the manual switch in the cab?

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    roadranger is offline Board Regular
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    Update on my stuck fan clutch:
    The fan clutch was working before the truck was parked for six months. Today I went to mess with it and decided that the air leak wasn't big enough to cause it to stop working. I read in one of the manuals I have for it that the clutch can get "stuck" and tapping it with a hammer would get it loose again. I hate to play "hammer mechanic" but damned if tapping on the three back pates that hold the lining in didn't get rust powder puffing out. It didn't immediately start turning right by hand but after starting it and running down the road a bit I noticed my shifting sucked - with the fan off it takes about twice as long as before for the engine to slow down enough to catch the next gear :shock: . BIG difference on running downhill too - that fan was soaking up a lot of horsepower and now I have to use the brakes a lot more.

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    GMAN's Avatar
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    It is amazing what you can do with a hammer and brute force. :lol:

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