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Fan clutch

Created On Sunday 1, February, 2009 10:34 PM by LBRacing

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LBRacing

Posts: 5
Joined: Jan 2009

Sunday February 01, 2009 22:34

I have a 2000 Freightliner Century with a 12.7 60 series. The truck has not been very well maintained and has several issues, I will tackle one at a time. The fan comes on when the air pressure reaches 75psi regardless of the coolant temp. I had someone with a Data Link check it and the coolant temp seemed to be reading correctly. If I connect a battery directly to the air valve it will function and the fan will stop. If I disconnect the plug from the air valve and check it with a volt meter I get 13 volts, if I check the voltage from the battery jumper lug near the firewall to the ground side of the plug (with it disconnected from the valve) I get 13 volts. If I reconnect the plug to the valve and check voltage from the battery lug to the ground side of the plug I get 0 volts. The truck shows the following inactive codes 54,43,22,36,34,16,31,46. Thanks for your help

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stonefly

Posts: 286
Joined: Feb 2008

Monday February 02, 2009 09:43

I have a 1993 Series 60. I had a similar problem, but the opposite was occurring. The fan was not turning on when the engine was hot. The problem was corrected by replacing the temperature controlled switch on the front of the thermostat housing.

On my engine, the switch has nothing to do with the ECM and it is not a sensor, per se. It has one function only. It turns on the fan when it closes, by actuating the air solenoid to the fan clutch. My engine did not come with a fan override switch. I installed one myself. I used the fog light switch, because I don't use fog lights and removed them from my truck. I ran wires from the fog light switch to the two terminals on the temperature controlled switch. I flip the fog light switch and that overrides the temperature controlled switch. This turns on the fan regardless of engine temperature.

I do not know if the air solenoid on your engine is hooked up to a switch similar to the one I described that my engine has.

On my engine, one side of the air solenoid goes directly to ground. The other side goes to one terminal of the temperature controlled switch. The other terminal of the temperature controlled switch has voltage on it. When the temperature of my engine gets to 200 or 205 degrees, the switch closes and puts voltage on the air solenoid. That closes the solenoid and removes air pressure from the clutch. The clutch then engages and turns on the fan. My fan clutch is engaged when no pressure is applied. It is the opposite of yours, which is engaged only when pressure is applied. I have a CAT with a fan clutch like yours.

I think you must have a bad connection somewhere. The solenoid does not draw that much current. If you are measuring battery voltage at 13 volts with the plug to the solenoid disconnected, and 0 volts when the solenoid is connected, then the place where you are measuring the battery voltage must not be a solid source of current. It must have a bad connection. The only way the solenoid could draw voltage down to zero is if the source of that voltage could not provide any significant amount of current. This could happen from a bad connection. It reads 13 volts only if there is no current draw. The slightest current draw drops the voltage to zero. That's it. There's a bad connection somewhere.

If you did have a switch similar to the one on the front of my thermostat housing, and it was faulty, it could easily cause the problem you are experiencing. You measure 13 volts when there is no circuit hooked to that voltage. As soon as a circuit is hooked to that voltage source, the voltage drops to zero. The switch might be corroded where it does not pass enough current to operate the solenoid, but when disconnected, shows a voltage. It happens all the time. It's also possible that the ground point where you are measuring is not a good ground. One way or another, you must have a bad connection. It's either a bad connection on the voltage side, or a bad ground. A solenoid simply does not draw enough current to cause a zero voltage between its voltage side and its ground side. It's impossible...unless the voltage side has a bad connection, or the ground side has a bad connection. If you do have a temperature controlled switch for your air solenoid, that could be where the bad connection is, the contacts of that switch. Follow the wires from your air solenoid. Find out where they go.

I don't know if this helps, I hope it does.

stonefly

Edited: Monday February 02, 2009 at 19:36 by stonefly

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stonefly

Posts: 286
Joined: Feb 2008

Monday February 02, 2009 19:48
<< If I connect a battery directly to the air valve it will function and the fan will stop. >> When you do this, are you also connecting a ground to the air valve? stonefly

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LBRacing

Posts: 5
Joined: Jan 2009

Monday February 02, 2009 22:39
I disconnected the air valve from the truck and connected a 12 volt battery to it. When I do this the fan will stop, this tells me the valve is working.

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stonefly

Posts: 286
Joined: Feb 2008

Monday February 02, 2009 23:29

Now you have to find out why the 12 volts from the truck's electrical system will not activate the air valve.

The air valve has two wires coming from it. One of those wires has to go to a good ground, and the other has to go to a good source of voltage. Without knowing what the wiring configuration is for your system, it's difficult to advise. However, I believe the first step should be to see if you have a pressure operated switch like the one on my engine. If you do, you may find the answer to your problem right there. It may be difficult to follow the wires if they are inside a harness cover, but you need to see where the wires from your air valve go.

If a voltage across your air valve shuts off the air to the clutch, then I would think you are looking for a switch that is normally "on", and switches to "off" when your engine reaches 205 degrees. That is the opposite of the way my engine works. On your engine, assuming it also has a temperature controlled switch for the air valve, the switch would turn "off" at 205 degrees, which would deactivate the air valve, and cause the fan clutch to engage.

As I said before, the switch on my engine is located on the front of the thermostat housing, right below the upper radiator hose.

stonefly

Edited: Monday February 02, 2009 at 23:35 by stonefly

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westcoast

Posts: 982
Joined: Dec 2008

Tuesday February 03, 2009 02:47

You need to find out if it is mechanically or ecm controlled ! If it,s mech it will have a Index horton switch in the thermostat housing with two screws coming out the top ( Brass sender with 7/8" socket head ) . If not it will have two temp senders - a single pin sender in thermostat hsg and a two pin sender in rear of cylinder head ( ones for the truck gauge and the other is for the ecm ) . --- If it,s mech it uses temp sender / overide switch and aircon pressure switch to break the circuit and turn it on . If it,s ecm controlled , the digital output is open to turn fan on and d/output is switched to battery ground to turn the fan off

-------------------------
detroit

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JohnnyReb

Posts: 32
Joined: Jan 2009

Thursday February 05, 2009 22:00
Make sure to check the hight pressure switch for the AC. Sometimes they go out and cause the fan to stay engaged.

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LBRacing

Posts: 5
Joined: Jan 2009

Friday February 06, 2009 12:50

There is no sender of any kind in the thermostat housing, there is a large pipe plug where one could go facing rearward. Also there are 2 empty wire looms attached to the right side of the head behind the thermostat housing just below the valve cover. I wonder if someone has removed the sender and wire(s).

There is a sender in the right side of the head just below the valve cover, I think it has one wire.

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westcoast

Posts: 982
Joined: Dec 2008

Friday February 06, 2009 15:31

G,day LB , Some freightliners had a two pin sender in the rear of thermostat housing ( Deutch plug ) for horton/cab temp gauge but normally the ecm sender is placed on the right hand side of head where the three 1/2" plugs are ! and the loom for this runs around the back of the head , what type of plugs have been left off ? . The single pin sender will be your cab gauge but it sounds like somebody has tried to hard wire the horton system for what ever reason Regards David

-------------------------
detroit

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LBRacing

Posts: 5
Joined: Jan 2009

Friday February 06, 2009 16:31
I am a little confused, is there always supposed to be a sender in the thermostat housing?

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stump

Posts: 814
Joined: Aug 2007

Friday February 06, 2009 16:49

LB also look at the A/C lines at the condenser up front there should be a switch in the liquid line going too the condenser coil up in front of the radiator.I t should have 2 wires coming off of it. If the switch is closed this can cause the fan too stay on also. It is designed to cycle the fan based on the high pressure in the A/C so on a hot day the fan will cycle on and off as needed. If the switch has gone bad and is staying closed that can keep fan engaged.Unplug switch and see if fan stops turning.

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stonefly

Posts: 286
Joined: Feb 2008

Saturday February 07, 2009 01:20

<< ...is there always supposed to be a sender in the thermostat housing? >>

I'm only guessing here, but if you don't have a temperature controlled switch on the front of the thermostat housing, your fan is probably ECM controlled. My engine has the switch on the front of the housing, and a sensor on the rear of the housing. I don't know what the sensor on the rear of the housing is for. I also have a sensor in the rear, right of the head, below the valve cover. I don't know what it does either. However, the one on the front of the housing is the fan switch.

You probably have an ECM controlled fan. If you do, a bad connection somewhere in the wiring between the ECM and the air valve could be the problem rather than an expensive ECM. That's what I'm hoping. I still think you have a faulty electrical contact somewhere, even if it is in one of the switches for the AC.

stonefly

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westcoast

Posts: 982
Joined: Dec 2008

Saturday February 07, 2009 05:28

Stonefly is right I think yours is ecm controlled , If your truck temp gauge works you must have a sender somewhere on your engine ,If your mate plugged into your truck and said the coolant gauge was working you must have an ecm sender !! ( r/h/s just above exhaust manifold ) You just need to trace it through --- if you say you,ve got voltage at solenoid plug then you have a grounding problem Regards David

-------------------------
detroit

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JoeZ

Posts: 938
Joined: Dec 2008

Saturday February 07, 2009 07:26

Just taking a shot in the dark here, but I have had occasions where I could read positive 12 volts with no load, but under the load, I would have nothing. Upon tracing the wire back, I would find a place where the insulation was pierced and then turned green and nasty on the inside. It would show voltage enough to light a test light, but not carry a load. I try to avoid stabbing wires, but if there is no other choice, I always clean and seal the puncture afterward. You might want to trace the wire back to the source.

-------------------------
One of the last 2 Stroke mechanics left.
44 years in the business and worked on everything from 53 series to 149 series. Winding it down now...time to move on.

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GoneFishen

Posts: 1325
Joined: Jan 2007

Saturday February 07, 2009 10:10

The fan is turned on by the engine ecm on the temperatre at 205*F. The fan switch on the firewall has a 12V hot wire and a wire that goes to ground. Since you say you have 12V, just ground the other wire and the fanshould go on. disconnect and the fan should go off. However the engine fan circuit provides the ground signal for the cooling only on this year truck. The ground signal is further down in the dashboard on a relay. The relay is also tripped for the AC sytem. You have 2 systems here at work. Engine cooling and AC operation.

-------------------------
DDA tech for 30 years,all 2 cycle,series 60,50 mbe also.
1995 F250, 191k mi.
Lost Wages, Nv

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LBRacing

Posts: 5
Joined: Jan 2009

Saturday February 07, 2009 21:14
I unplugged the AC pressure switch and the fan still runs any time the air pressure is above 75psi. I checked the pressure switch with a meter and it is open (lots of ohms). Thanks

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westcoast

Posts: 982
Joined: Dec 2008

Saturday February 07, 2009 21:25
Hop in your truck , start it build up air - turn truck off . Turn ignition on - listen as you do so - you should hear at least two relays tripping --Your ignition relay and your fan enable relay , With air built up when you turn your key on if your fan enable relay is working the fan will disengage - if not start there !!! Regards David ------------------------- detroit

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DTXMechanic

Posts: 9
Joined: Jan 2009

Saturday February 07, 2009 23:15

hello all, our freightliner trucks fans are controlled by the ecm but they "release when air is sent TO the clutch" we see this as the fan is locked with engine off and no air and runs until approx 75psi is reached, could someone have changed this fan clutch and put on the wrong type? also our trucks do not send the elec signal through the A/C switch instead the a/c switch sends a signal to the ecm at approx 350 high side psi to turn on the fan for a minimum of 5 minutes, we see this because the fan will not turn off until it "times out" regardless of high side a/c pressure or even if you turn the a/c off. The fan soleniod gets voltage all time key is on, and the ecm sends a ground to 1-energize the soleniod 2-send air to the fan clutch and 3- RELEASE the fan. As someone mentioned before you can hear this by with the engine off and air in tanks, turn the key on (fan should spin freely) turn the key off and you should hear the air release from the clutch through the bleed muffler on the soleniod and the fan should lock up.

-------------------------
mostly series 60 and MBE 926/4000

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