IK0900094 - Horton VMaster Ultra (Stratis) Viscous Fan Hub Diagnostics and Troublesh... Page 1 of 19

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Title : Horton VMaster Ultra (Stratis) Viscous Fan Hub Diagnostics and Troubleshooting Guide
Applies To : ProStars, LoneStars, WorkStar, TranStar, IBB

CHANGE LOG
Dealers: Please refer to the change log text box below for recent changes to this article:
6/19/2014 ­ Initial Article Release: IK0900075 was combined with this article.
6/24/2014- Updated Article title
6/24/2014- Remove information about Anti Rotation Bracket, it is cover with the Harness Re­Route Procedure
6/24/2014- Updated Part number for Horton ILD 800922R91
6/27/2014 - Added information from PL3000024: Recall Serial Numbers of Horton Fan Drive and reformatted
entire article.
7/6/2014 - Removed links that were not working





CONTENT MENU

N13 and EPA10 MaxxForce 11/13
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•
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General Fan Operation
Visual Inspection for Fan Drive and Wiring
Electrical Inspection of Control
Engine Fan Test
Engine Fan Results
Harness Reroute Procedure
Fan Engages Prematurely
Part Recall Information

EPA07 MaxxForce 11/13
• Visual Inspection for Fan Drive and Wiring

DESCRIPTION
This article is a Troubleshooting Guide for the Horton VMaster Ultra (Stratis) Viscous Fan Drive.
Engine feature code: 12THX
General Fan Operation (All Engines):

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Horton VMaster is a variable speed drive. It does not function like an on/off drive. Even when the drive is off the fan will
spin between 50‐300 rpm.
When drive is commanded off by ECU, fan speed should be 50 to 300 rpm. When drive is commanded on by ECU, fan speed
should be approximately 125% of the engine speed. For Example: At 2100 engine rpm x 1.25 fan drive ratio, the fully
engaged fan speed should be approximately between 2490 and 2600 rpm
The default state of the fan is ON. The ECM or EIM uses a pulse width modulated (PWM) signal to turn the fan OFF. This is
described in more detail in the information provided for each engine platform.
After first start of the day (A/C in off position) time for fan to disengage; at high idle (2100 engine rpm), disengagement
may take up to 2 minutes after disengagement command, depending on the ambient temperature and at low idle (600
engine rpm), disengagement occurs approximately 25 to 30 minutes after disengagement command.
Warm truck (A/C in OFF position), time for fan to disengage; at high idle (2100 engine rpm), disengagement occurs
approximately 20 seconds after disengagement command and at low idle (600 engine rpm), disengagement occurs
approximately 25 to 30 minutes after disengagement command.
CAUTION :
This fan clutch has left hand threads.
The default state of the fan is ON. Ground is required to turn the fan OFF (refer to the two figures below).
• ECM C1‐18 controls the fan by supplying a Ground PWM signal
• ECM C1‐58 is feedback for the fan speed

Wiring Diagram of 2010 Fan

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Chassis Connector 6420
Front side

Fan Hub Assembly
Connector

N13 and EPA10 MaxxForce 11/13
INSPECTION STEPS
Visual Inspection for fan drive and wiring:
NOTE: The visual inspection steps are the same for EPA07 MaxxForce 11/13.
1. Check for rubbing on wire:

‐ If rubbing is present and inside wires are visible, but no copper is visible apply heat shrink over the harness.
‐ If copper can be seen, check to see if it is only one single wire, or multiple wires.
If it is one wire, place electrical tape over the wire.
Using 4:1 heat shrink will allow the heat shrink tubing to pass over the connector as shown. P/N: ZBJE849565 or
equivalent

If multiple wires are showing copper, remove and replace the fan hub assembly.
‐ Reroute the wiring harness at outlined in the "Harness Re‐Route Procedure" in this iKNow article.
2. Check to see if ARB is touching the target wheel. Refer to Figure 1 and Figure 2.
‐ If it is touching, reposition ARB to clear the target wheel as shown in Figure 1.
3. Check to see if the target wheel is loose, moves, or spins freely.
‐ If it is loose, moves, or spins freely replace the fan hub assembly.
‐ An improperly positioned ARB or loose target wheel can cause the damage in Figure 4.
4. Pull / Push fan ON ‐ refer to Figure 5.
‐ Rotating the fan by hand, the hub should provide a smooth and consistent resistance.
‐ If it rotates freely approximately 1" or more before resistance is felt, replace the fan hub assembly.
‐ If you have any questions on this process, call Horton customer service for assistance at: 1‐800‐621‐1320

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Figure 1

Figure 2

Figure 3

Figure 4

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Figure 5
Electrical Inspection of Control:
1. Ensure the truck is turned off and the key is removed from the ignition.
2. Unplug the fan hub from the chassis connector.
3. Using a digital multimeter, measure the resistance between pins on the fan hub Deutsch connector.
‐ Terminal 1 to Terminal 2 (1‐2) Spec ( >1MΩ )
If it fails this test, use In Line Device (ILD) shown in photo. This failure is usually associated with a 3512 code.
‐ Terminal 1 to Terminal 3 (1‐3) Spec ( 6Ω to 16Ω )
‐ Terminal 2 to Terminal 5 (2‐5) Spec ( 2.5KΩ to 4KΩ )
If it fails this test, replace the fan hub assembly.
‐ Double check any resistance that are out of spec to ensure an accurate reading
SPN FMI

Description

3

EFC Short to PWR

4

EFC Short to GND

5

EFC Open Load / Circuit

3

EFS Unrealistically HIGH

1639 4

EFS Unrealistically LOW

647

8

Repair Procedure

Check coil resistance
Spec: 6 to 16
Replace fan hub assembly if out of spec ‐ EPA 10 Only.

Do not replace the fan hub assembly
Update ECM calibration to 3.5.4 or later

EFS Frequency Signal Error

VREF4 Voltage Deviation
ECM Terminals:
3512 14
C1‐37, C1‐43, C1‐49, C2‐08, E1‐58,
E1‐91

Install Horton ILD (In Line Device) P/N 8000922R91
Replace fan hub assembly if both codes 3512 and 647 are present ‐
EPA 10 only

Engine Fan Test:

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NOTE: The 'Engine Fan Test' is not available for the EPA07 Engine.
1. Manually apply 12 volts to Pin 3 and Ground to Pin 1, checking fan operation. It should be disengaged. Some surging may
be normal depending on the temperature of the fan hub.
2. Bring engine to operating temperature. 175°F‐180°F.
3. Connect with ServiceMaxx and perform "Engine Fan Test" (Figure 6).
4. The entire test (5 test points) must be recorded and submitted with the warranty claim (Figure 7).
5. If the visual, electrical and functional tests all check OK, the fan hub is not the cause of the customer complaint. Do NOT
replace the fan hub.

Figure 6

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Figure 7
Engine Fan Test Results:
1. You will need to monitor the entire fan test while it is running to determine if the fan has passed or failed.
2. The fan needs to operate within the limits at each test point. The fan should engage and remain engaged during the
entire engagement request.
3. The actual fan speed should be approx ± 250 RPM of desired. Some viscous properties of the fan hub may vary the
results. See examples below (Figure's 8, 9 & 10).
4. Notice in the chart below (Figure's 8, 9 & 10), when the engine ramps with 0 RPM desired fan speed, the fan does pick up
some speed. This is normal due to the viscous properties of the fan hub.
4. Also as Item 3 points out (Figure's 8, 9 & 10), the engine speed and desired fan speed nearly match. If the fan is
requested on 100%, the fan may actually engage at 125% of engine speed as shown.

Figure 8 ‐ Properly Working Fan Hub Assembly
1. The engine ramps to the same speed for each section of the test.
2. When the ECM is no longer requesting a set fan speed, the fan disengages. However,
as the engine ramps to start the next section of the test, the fan speed increases. This
is normal due to the viscous characteristics of the fan hub. As the fan hub stabilizes
you see the fan speed then continues to decrease.
3. This section of the test shows the fan speed higher than the desired fan speed. This is
due to engine speed and desired speed being very similar values. The fan is then
commanded ON, and the fan speed is 125% of desired. This is normal.
4. This is showing the duration of the fan on command. Notice in each section the fan
does not match up and perfectly align. This is due to the PWM (Pulse Width
Modulated) signal that is being sent to the fan hub.

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◦ You can review your fan test in ServiceMaxx to see a chart view of the signals
shown in this chart.
◦ If you have any questions of the results, attach your fan test snapshot to your
case file for review.

Figure 9 ‐ Properly Working Fan Hub Assembly (Example 2)
1. Again, notice the fan speed varies when the engine ramps for the first time and
desired fan speed is zero. This is normal due to the viscous properties of the fan hub,
and is normal operation.
2. The Fan Control % has been added to this chart.
3. As stated in the chart above, due to the engine speed and desired fan speed being
very similar values, the ECM commands the fan on at 98.04%. However, in this test
the ECM tries to change the fan speed by changing the fan control percent. The fan
control percent drops near zero to attempt to achieve this. While this is a different
reaction for this portion of the test then the chart above, it is still normal operation.
◦ You can review your fan test in ServiceMaxx to see a chart view of the signals
shown in this chart.
◦ If you have any questions of the results, attach your fan test snapshot to your
case file for review.

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Figure 10 ‐ Failed Fan Hub Assembly
1. Engine ramps to the same speed for each section of the test.
2. When the ECM is no longer requesting a set fan speed, the fan disengages. However,
in this example, the viscous portion of the fan is not responding, allowing the fan
speed to drop off rapidly.
3. Notice the fan speed is always engaging to over 2000 RPM. The fan is turning on fully.
This is not normal operation for the fan test.
4. This is showing when the fan is commanded off, the fan hub speed increases with
engine speed. Fan speed never drops back off, as shown in the working fan example
above.
◦ Note: This is one example of a failed fan. Not every fan hub will fail this way.
◦ You can review your fan test in ServiceMaxx to see a chart view of the signals
shown in this chart.

5. The "Test Completed, Successful" (Figure 11) window at the conclusion of the test does not indicate the fan has passed.
It only indicates the test has been completed successfully. You will need to determine if the fan has passed or failed.

Figure 11

EPA07 MaxxForce 11 / 13

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