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Thread: Engine temperature

  1. #21
    Join Date
    Apr 2019
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    Arlington
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    Thanks guys. I have been too busy to follow up on this any more. I am going to make sure the fan actually goes to high speed when I get a break. I dont recall it being as loud as some describe it when its on high. I was reading another post where someone added some small LED lights that indicated fan speed. That would be fun to have.


    Mark and Debbie Fratto
    1998 Parliament

  2. #22
    Join Date
    May 2012
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    Beverly Hills
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    Loc, your results are very similar to those reported by others. I know my results on my last 99 and now on my 03 were very similar.

    Thanks for the post.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

  3. #23
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    Apr 2019
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    Arlington
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    I finally had a chance to look at this again. Before I started the diesel, I held the fan pulley still and could not rotate the fan. Then I started the diesel. As soon as the air built up to tension the drive belts, they chirped and the fan started to turn. It was blowing enough air that you had to hang on to the engine access doors when opening them. Then I turned on the AC compressor and the fan speed did not change. So it would appear that my fan clutched is locked in or perhaps replaced with one that is not two speed? I looked and did not see any wires going to the hub.

    Also, I do not have transmission temp gauges etc. Does anyone have a recommendation for a meter that would plug into the DDEC to provide some real time information?
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    Mark and Debbie Fratto
    1998 Parliament

  4. #24
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    Nov 2018
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    PIEDMONT
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    Are these fan clutches two speed? I've never had a definite answer to that question. My chassis has OTR A/C so no condenser in front of radiator. I've somewhat come to the conclusion that the "HIGH FAN" switch simply engages the fan clutch. Fan will spin otherwise ("HIGH FAN" off) but is simply freewheeling due to the fan drive spinning.

    I have a relay socket in rear engine electrical cabinet marked "LOW FAN" but there was no relay there. When I had Carrier compressor shaft seal replaced by a charter bus mechanic I asked him about the empty relay space. He said he was pretty sure OTR A/C chassis didn't have a relay there. He put one in to check, nothing changed so left it for me as a spare.

    If any of this is incorrect I'd like to know. Mine will get to 205-210 range without "HIGH FAN" switch turned on. That will bring it down into the 190's.

    Billy & Lisa Gaines
    1996 Marathon XL40

  5. #25
    Join Date
    May 2012
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    Beverly Hills
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    Mark,

    Turn the ignition to off. Is the fan still locked? If so, there's something wrong with the clutch or it's manually locked. It doesn't locked locked as I can see the lock bolts.

    If it wasn't locked in the last step, turn the ignition on but don't start the engine. Is it locked? If so, pull the low and high speed fan relays one at a time and see if the fan is still locked. If it's locked in either one, replace the relay or swap them to see if the one that locked it moves when you swap the relays. If a relay replacement does not unlock it you have a problem with the ground coming from the DDEC.

    Billy, how did you determine putting a relay in the low speed slot had no affect on the clutch. I can't imagine what bus air has to do with the fan clutch as bus air doesn't need the radiator fan to turn.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

  6. #26
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    Nov 2018
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    PIEDMONT
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    466

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    Gil, bus was in shop on high idle when relay was put in. Fan was moving somewhat - freewheeling - that never changed. Nor has it changed since. Only way to bring engine temp down in the 190's is to turn on the "HIGH FAN" switch. Same as before additional relay was added.

    I only mentioned mine has bus air so there wouldn't be any confusion regarding fan clutch engagement / dash air / radiator mounted condensers, which this one doesn't have. There was discussion earlier about the dash air system causing fan clutch operation - just wanted to be clear this one doesn't have any of that.

    Billy & Lisa Gaines
    1996 Marathon XL40

  7. #27
    Join Date
    Mar 2013
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    Chicago
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    3,988

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    The wire lead is forward of the hub going thru a hole in a bracket forward of the hub. There r additionally 2 eyelets they run the wires through that r in a location that r impossible to loosen without pulling the whole carrage.

    So often, removing the old one gets done buy cutting the wiring and pulling them out of the eyelets.

    Ive seen countless leads on the replacement ziptied up to those eyelets because of this and worse yet just lying in there. Be sure its secure the leads r over length and can lay on the oil cooler if not sufficiantly fastened.
    Last edited by Joe Camper; 08-28-2019 at 08:13 AM.
    1990 Peterbuilt 377
    3406 B Caterpillar
    13 Speed Roadranger
    No Norgrens


    1 day on paper no machines

  8. #28
    Join Date
    Jan 2006
    Location
    Pinehurst
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    953

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    Joe,

    The difference in my temps was due to the fan not being locked up. When locked up, the temps were very predictable even in high outside temps and the bus runs cooler than when the fan is not locked up. When not locked up, temps got up to the 210 level then the fan kicked in and brought them back down.

    Loc - 2008 Marathon XLII - Houston

  9. #29
    Join Date
    Apr 2019
    Location
    Arlington
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    871

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    I checked the fan and it was locked up with the key off and both the 12V and 24V engine bay switches in the off position. I will double check this again this weekend to make sure. As I understand it, the fan has electo magnets and they will not lock up without power is that right? Assuming that is is locked up without power, is that an automatic replacement of the clutch or can we drive it and just not have two speeds?

    Assuming that it is locked then that would be high speed so that would not be the reason for running a higher temp with the dash air one right? Unless the belts were slipping or something like that.


    Mark and Debbie Fratto
    1998 Parliament

  10. #30
    Join Date
    May 2012
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    Beverly Hills
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    Mark, even though I could see the locking bolts weren't used, you should make sure the clutch does not have locking bolts installed. I've never heard of a failure mode where the clutch locks. And yes, it takes power to lock the clutch. Although it should not be powered with the key off, try pulling the main fan relay. I think it's R99 on your coach. Look at the relay decal on the door to make sure.


    Gil and Durlene
    2003 H-3 Hoffman Conversion

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