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tjc transport

CV-713 fan clutch stays locked.

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hi guys, new poster but old trucker here.

i ran into an issue with a 2005 CV-713 Granite triaxle dump truck.

427 engine, with eaton fuller 8LL trans.

the past few weeks the fan clutch has had a mind of it's own. sometimes it works perfectly, other times it stays locked all day long.

it lockup today, and i finally had a test light with me in the truck to do some pinpoint testing.

i removed and cleaned the connections on all the fuses and relays in the engine bay fuse compartment, and now have power to both side of alll the fuses.

this made the ABS light go out, and the reverse light come on when put in reverse. but the fan stayed locked on.

i have 12 volts to the air switch on the firewall, but no ground.

the ground for the switch is computer controlled, correct?\does this sound like a bad temp sending unit, or a bad computer?

when the fan clutch is working properly, engine temps stay rite around 165 degrees, unless i pull a long hill loaded, then it will creep up to arouns 200 degrees and the clutch locks up. once temps drop to around 180 or so, the clutch unlocks, and if on flats the temps drop back down to 165.

oil temps are also around 150-165, unless coolant temp climbs up, then the oil temp rises accordingly. and once the coolant temps drop the oil temps drop also.

with the clutch locked up all hte time coolant temps stays around 150 no matter what i am doing.

i would really like to resolve this issue, because it sounds like a F-16 driving down the road with the clutch locked up.

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12 volt power goes through the air solinoid all the time. The engine ECM grounds it internally , when the ECM tell it to engage it breaks the ground and fan engages. High water temp, high intake air temp and A/C high pressure will engage fan. With engine off, shoot air into fan clutch and see if it disengages. That will rule out the fan clutch its self. Make sure you have system air pressure going to solinoid (130 + or -). Other wise have a laptop hooked up to it and check switch status to see whats engaging it.

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i have since grounded the switch and the fan unlocks.

if the air conditioner is kept off, the fans stays unlocked.

as soon as the air contitioner is turned on, the fan locks up and stays locked until the engine gets cold and all air is drained from the system. then it will stay unlocked until the air is turned back on again. and it does not matter is the pressure switches in the air conditioning system are connected or not.

also, the air conditioning does not work at all.

if i put 12 volts directly to the clutch on the compressor, the ac works and pressures are correct, 35 low side 290 high side. until the 12 volts is removed.

both high and low pressure switches can be disconnected, as soon as i push the AC button on the temp panel the fan locks up and stays locked until no air/cold engine is reached.

Edited by tjc transport

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The AC high pressure switch should be a green and round and opens at 300 psi. Is someone installed the wrong switch or got it plugged into the wrong place it could make the ECM think the AC head pressure is over 300 psi

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but once the high side pressure drops below 300 the fan should turn back off correct?

with this truck, the clutch will not disengage until the engine gools off the air system is drained.

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The fan can stay engaged for awhile after the high pressure switch it opened. Usually its set at 60 seconds. This a parameter that can be changed in the engine ECM. Factory setting is 60 seconds.

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The fan can stay engaged for awhile after the high pressure switch it opened. Usually its set at 60 seconds. This a parameter that can be changed in the engine ECM. Factory setting is 60 seconds.

that is what i thought.

once the clutch engages, it stays locked up until the engine cools off and all the air is drained out of the tanks.

today it came on at 8:15am as i was pulling a grade loaded.and stayed locked until i parked the truck at 3:35pm which was a little different than normal,

normally the clutch works as it should, comes on at 200 degrees and shuts off at 185 or so, unless the ac is touched or the defrosters are turned on. then it stays locked until engine is cool and all air drained out of the tanks.

Edited by tjc transport

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to add to the confusion with this truck.

the boss replaced a 1/2 inch synflex line in the driver side frame that was leaking last night.

the line would leak out all air in about 4-5 hours sitting engine off.

today i tried the ac at 11:30 because i noticed the fan did not come on all morning. the AC now works, and the fan stayed off until i hit a grade and temp got up to 200. cooled off to 180, the fan turned off, and stayed off for the rest of the ride home.

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