Working Fan Clutch of the HUMVEE – Hummer

31 05 2012

ImageTijdens het repareren en onderhouden van mijn humvee zoek ik via mijn netwerk en via internet veel informatie die ik kan toepassen. Voor de werking van de “Fan Clutch” – koel ventilator heb ik een de volgende goede beschrijving gevonden:

Part I
The cooling system for the HMMWV has always been a nightmare to troubleshoot
and repair. Most people just start replacing things and wait to see what
happens.

The major components of the system are:
a) the Kysor/Cadillac solenoid that switches the hydraulic fluid to the fan
actuator on and off
b) the time delay module that is actually a time delay on turnoff unit that
keeps the fan energized for a period of time AFTER it hits the cool down
setpoint
c) The fan clutch actuator that engages and disengages the fan itself
d) the temperature sensor that lives in the water crossover pipe on the top
of the engine.

The fan clutch can be tested by removing the belts and applying ~90 psi air
to the hydraulic line. If the clutch is working it should move front to rear
as pressure is applied and removed. With no pressure the clutch is locked
and drives the fan, with pressure the fan is unlocked and should spin.

The solenoid can be tested by teeing a pressure gauge into the hydraulic
line and monitoring the pressure. With the engine cold there should be
pressure on the line disengaging the fan to help heat the engine. When the
sensor detects the engine is hot the pressure should drop off engaging the
fan. After the engine is hot you can cycle the fan by connecting and
disconnecting the TDM plugs. Disconnected the fan should run continuously.

The TDM can only be tested by substitutionas far as I know.

The temp sensor is a switch that actuates when the engine is hot. Remove it
from the engine and hook an ohmmeter to it. You should see it switch by
dipping it into a pot of boiling water. I don’t know if a hair dryer would
be hot enough and a heatshrink gun might be too hot and ruin the sensor.

Part II
The easiest way to test the temp sensor is to wire a simple toggle switch
with two pigtails to connect to the leads, switch on => fan should
freewheel, switch off => the fan runs.
As has been stated if the TDM is disconnected the fan runs continuously.
Testing of the TDM can be done with the TM directions.
The solenoids seem to get blocked on the hydraulic side, mine still worked
(you could feel it operating) but the fluid was never coming out.
The section in the TM is TM 9-2320-280-20-1 pages 2-159 – 185 inclusive.
Put a gauge in between the line on the solenoid so as to see if there is any
pressure going out to the Fan clutch unit…
if not enough remove the solenoid and use compressed air to clean it out…
reïnstall en to measure press in the line out going to the fan clutch unit.
If fan indeed freewheels then disconnect TDM and fan should run.

Part III
The fan clutch is hydraulically controlled for “locked” or “unlocked”. It uses power steering fluid pressure routed through an elctro-hydraulic solenoid that locks up the fan clutch just like a clutch pack would be in an automatic trans. The solenoid operated (to lock the fan clutch) by the small black box next to it in the pic. The fan clutch on these is either completely on (spinning at water pump speed) or completely off (free wheeling)…. no in between.

Normally, the fan cannot be engaged manually by the driver. In other words, there is no “switch” inside the hummer to turn the fan on whenever they want. It is managed and turned on or off automatically based on engine temps. However, in a pinch, unplugging the black box next to the fan solenoid will make the fan on continuously.

V-belts and serp belts are both used on hummers, it all depends on the model. V-belt’s use CW water pumps while serp belt systems use CCW HO pumps just like the civilian trucks.
This is some info out of the Hummer operator’s manual, which is kinda like an owners manual.
This is for “light duty” (more or less, to break it down in easy to understand terms) Hummers
Table 1-6. Cooling System Data
Surge tank cap pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 15 psi (103 kPa)
Thermostat:
Starts to open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190°F (88°C)
Fully open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212°F (1 00°C)
Radiator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Downflow type
Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 blade, 19 inch (48 cm)
Normal operating coolant temperature . . . . . . . . . . 190°-230°F (88°-110°C)

And this table is for “heavy duty” hummers.
Table 1-5. Cooling System Data.
Surge tank cap pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 psi (103 kPa)
Thermostat:
Starts to open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190°F (88°C)
Fully open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212°F (100°C)
Radiator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Downflow type
Fan (serial numbers 299999 and below) . . . . . . . . . . . . . 10 blade, 19 in. (48 cm)
Fan (serial numbers 300000 and above) . . . . . . . . . . . . . .9 blade, 23 in. (58 cm)
Normal operating coolant temperature . . . . . . . . . . . . . . 185°–250°F (85°-120°C)
Notice the “normal operating coolant temprature” ratings on each one………..

Here’s more stuff out of the operator’s manual:
ENGINE TEMPERATURE SWITCH – Sends signal to activate control
valve system to operate fan when engine temperature exceeds 220°F (104°C)
and deactivates control valve system when engine temperature drops below
190°F (88°C).

HYDRAULIC CONTROL VALVE – Directs hydraulic fluid to provide
required pressure to actuate fan clutch as required by engine temperature.
Hydraulic pressure supplied by power steering pump.

FAN CLUTCH – Hydraulically actuated by pressure from hydraulic control
valve to control operation of fan. Hydraulic pressure supplied by power
steering pump.


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