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catmastertech
catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 2331
Experience:  19 years Cat, 3 years Case
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that controls forward and reverse is going..actually start..in neutral

Customer Question

Morning, we have a Cat 902, the the thumb switch that controls forward and reverse is going out, works for a while then won't go forward. You can actually start it while switch is in forward. It's not suppossed to start if it's not in neutral. Reverse switch seems to be working fine. Problem started a few days ago and this morning it finally just stopped. when you switch it to forward, the nuetral light just blinks. Checked all fluids and they are fine. Any ideas?
Submitted: 6 years ago.
Category: Heavy Equipment
Expert:  catmastertech replied 6 years ago.

Donnie :

It is common for these switches to fail. Have try to replace it yet?

Donnie :

It appears the whole handle will need to be replaced, do you have the serial number?

Donnie :

It has several versions for the different options.

Donnie :

I also see it has been updated a couple of time too.

Donnie :

Improved Modular Handle Group Is Now Used

Integrated Toolcarrier:
IT14G (S/N: FWL1-UP; KZN1-UP; 1WN1-UP)

Description of Change: An improved Modular Handle Group is now used on the above listed machines. These new Modular Handle Groups feature better design of mechanical switches in order to improve durability and reliability.

Adaptable To: The improvements were effective with the manufacturer's date code of 0501 (2005, week1). The affected parts are listed below:

 

  • 208-6093 Modular Handle Gp

     

  • 208-6096 Modular Handle Gp

     

  • 208-6097 Modular Handle Gp

     

  • 208-6098 Modular Handle Gp

IT28G (S/N: WAC1-UP; DBT1-UP)
Wheel Loader:
902 (S/N: 7ES1-UP)
906 (S/N: MER1-UP; 6ZS1-UP)
908 (S/N: TAR1-UP; 8BS1-UP)
914G (S/N: PDF1-UP; 9WM1-UP)
924G (S/N: DDA1-UP; RBB1-UP; WMB1-UP)
924GZ (S/N: RTA1-UP; WGX1-UP; DFZ1-UP)
928G (S/N: DJD1-UP; WLG1-UP)
938G Series II (S/N: RTB1-UP; CRD1-UP; PHN1-UP; B9Y1-UP)
938G (S/N: 4YS1-UP; 6WS1-UP; 8RS1-UP; 9HS1-UP)
950G Series II (S/N: BAA1-UP; AYB1-UP; AYD1-UP; AYL1-UP; AXR1-UP; AYS1-UP; AXX1-UP)
962G Series II (S/N: BAB1-UP; BAC1-UP; BAD1-UP; AYE1-UP; AYG1-UP; AXS1-UP; AXY1-UP)
966G Series II (S/N: AXJ1-UP; AXL1-UP; ANT1-UP; AWY1-UP; ANZ1-UP)
972G Series II (S/N: AXC1-UP; AXE1-UP; AXN1-UP; AWP1-UP; AXP1-UP; ANY1-UP)
Donnie :

Is your machine listed here?

Donnie :

I just found a guide for your problem, see if this will help you pin point the problem.

Donnie :

Symptom (Will NOT Go Into Gear) Neutral Lamp Flashing.

The transmission control will NOT engage the direction solenoids if the parking brake is ENGAGED. When the parking brake input (connector contact 42) is open the parking brake is ENGAGED. When the parking brake input (connector contact 42) is grounded the parking brake is DISENGAGED.

1. CHECK PARKING BRAKE - Check to see if the parking brake is DISENGAGED and the parking brake lamp is ON.

* Check switch adjustment. Remove parking brake cover to gain access to parking brake switch. With parking brake DISENGAGED. Measure voltage between the normally open (NO) pin (765-BR) and the common pin (201-BK). Voltage should be 0V.
* If operation is correct (parking brake lamp goes OFF) the transmission control and harness are correct. The parking brake switch is not the source of the problem.
* If operation is NOT correct. Go to Step 2.

2. Reapply parking brake. Measure voltage between the normally open (NO) pin (765-BR) and the common pin (201-BK). Voltage should measure 9.5V±0.5.

* If operation is correct the transmission control, parking brake switch, and harness are correct. The parking brake switch is not the source of the problem.
* If operation is NOT correct. Go to Step 3.

3. Check parking brake switch operation.

* If operation is correct the transmission control, parking brake switch, and harness are correct. The parking brake switch is not the source of the problem. Go to Step 4.
* If operation is NOT correct. Repair or replace switch. Repair or replace harness. Repair or replace ground.

4. CHECK FNR SWITCH - See FNR switch test charts located earlier in this text.

* If operation is correct. Go to Step 5.
* If operation is NOT correct. Replace FNR switch.

5. CHECK DIRECTION SOLENOIDS - Disconnect the direction solenoid connector. There is one four pin connector for both solenoids. The solenoids are located on the hystat pump body. Measure the voltage (on the harness) between pins 1 and 2 (Forward). The voltage should be 4.5V±0.5. Measure the voltage (on the harness) between pins 3 and 4 (Reverse). The voltage should be 4.5V±0.5.

* If the voltage is correct. Go to Step 6.
* If the voltage is NOT correct. Repair or replace the harness. See Step 7.

6. CHECK DIRECTION SOLENOID RESISTANCE - Measure between pins 1 and 2 (Forward). The resistance should be 5 ± 2 ohms. Measure between pins 3 and 4 (Reverse). The resistance should be 5 ± 2 ohms.

* If resistance is correct. Go to Step 7.
* If resistance is NOT correct. Replace the appropriate direction solenoid.

7. NOTE: If the FNR indicator lamps that light up the direction arrows and neutral lamp (located on the right side of the dash) are shorted to ground. The control may think the direction solenoids are shorted. These lamps are in parallel with the solenoids. The chance of this occurring is very rare. This short would have to sink in excess of 4.5A. This has NOT occurred in testing or in the field.

Donnie :

Here is the test chart list in the test.

Full Size Image

Donnie :

The connector is below the control lever covers and is connected to the ecm controller.

Full Size Image

Donnie :

If ANY fault occurs with the control module or system components the Neutral Lamp (right side of steering console) will flash.

NOTE: The transmission control is unlikely to fail. Access to the transmission control and connector is difficult. This troubleshooting guide is written to minimize accessing the transmission control and connector as much as possible.

NOTE: Avoid removing the TOP of the right side console. It is easy to remove but DIFFICULT to install. If you remove the top take the time to label the nine (9) connectors that must be removed from the switches to gain access to the transmission control.