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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 988
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I have a 420DIT The tool connected does not functionAlso I have a dire

Customer Question

I have a 420DIT
The tool connected does not function
Also I have a direct electrical short
In the instrument panel the fuse blows instantly when installed
If I remove the dash switch for the tool lock the the fuse holds and the instruments work
This has been very frustrating
My mechanic has been working on it for hours also he said we have no hydraulic flow at the directional valve body for the tool carrier
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 year ago.
Hello,I understand your frustration, this machine has seen lost of changes from early models.Please post the full machine serial number so, I can research this problem. I will be away for the day but, I will be glad to dig into this and post an answer for you tonight. If this is not helpful, I will OPT-OUT so other may help.Can you tell me the fuse number that keeps failing?How did this problem begin? Did the machine get damaged? Has any harness or parts been changed?
Customer: replied 1 year ago.
I added a photo of the Id Tag
No damage to the machine
Recent brake work
Brakes, and parking brake
The fuse that keeps blowing is P7
I have unplugged the toggle switch for the locking piston on the dash and the fuse holds
Sorry for the confusion on finding you answer this is the first time I have used this service
Please email me back at***@******.***
Expert:  catmastertech replied 1 year ago.
Thanks, ***** ***** serial number for parts and service is BLN06175 (last eight of the PIN)I did not find any issues that directly relate to this issue except the harness to the quick coupler has failed often.If you have not replaced this harness, test it for continuity. Here is a test sheet for the switch. You cannot do step one unless you have ET program so, skip to test step 2.The quick coupler is optional equipment. This feature is used in order to operate the quick coupler pins of the integrated toolcarrier. Before the feature for the quick coupler can be used, the auxiliary lines must be disconnected from the work tool and the lever on the ball valve must be placed in the HORIZONTAL position. The operator will then be able to use the switch for the quick coupler. Depressing the switch in the LOCKED position will energize the solenoid valve (quick coupler) and the modulating valve (auxiliary)(No. 2). The quick coupler pins will extend. Depressing the switch in the UNLOCKED position will energize the solenoid valve (quick coupler) and the modulating valve (auxiliary)(No. 1). The quick coupler pins will retract. Note: Check for any diagnostic codes before performing any of the following test steps. Check the auxiliary control for proper operation.Test Step 1. CHECK THE STATUS OF THE SWITCH Turn the key start switch to the "ON" position. Use the Caterpillar ET to check the status of the switch . Depress the switch in the "LOCK" position. Note the status of the switch. Depress the switch in the "UNLOCK" position. Note the status of the switch.Expected Result:With the switch in the "LOCK" position, the status should display "ENGAGED". With the switch in the "UNLOCK" position, the status should display "DISENGAGED".Results: OK - The status is displaying "ENGAGED" in the "LOCK" position and the status is displaying "DISENGAGED" in the "UNLOCK" position.Repair: The switch is working properly. See Troubleshooting Section, "Quick Coupler Does Not Operate".Stop. NOT OK - The status of the switch remains in the "OFF" status. Proceed to Test Step 2.Test Step 2. CHECK THE CONTINUITY OF WIRE 203-BK Turn the key start switch to the OFF position. Remove the switch from the dash. Unplug the switch from the wire harness. Measure the resistance of wire 203-BK of the wire harness to the machine frame.Expected Result:The resistance should be less than 5 Ohms.Results: OK - The resistance is less than 5 Ohms. Proceed to Test Step 3. NOT OK - The resistance is greater than 5 Ohms.Repair: The circuit is open in the wire harness or in a connector. Locate the open. Repair the wire harness or the connector or replace the wire harness or the connector.Stop.Test Step 3. CHECK THE CONTINUITY OF THE SWITCH IN THE LOCK POSITION Press and hold the switch in the LOCK position. With the switch in the LOCK position, check the resistance from terminal 2 to terminal 1 and to terminal 4. With the switch in the LOCK position, check the resistance from terminal 2 to terminal 3 and to terminal 6.Expected Result:The resistances should be greater than 5000 Ohms on terminals 1 and 4. The resistances should be less than 5 Ohms on terminals 3 and 6.Results: OK - The resistances are correct. Proceed to Test Step 4. NOT OK - The resistances are not greater than 5000 Ohms on either terminal 1 or terminal 4 or the resistances are not less than 5 Ohms on either terminal 3 or terminal 6.Repair: The switch has failed. Replace the switch.Stop.Test Step 4. CHECK THE CONTINUITY OF THE CIRCUIT WITH THE SWITCH IN THE LOCK POSITION Remove the operator control panel on the right side in order to get to the ECM. Remove the wire harness from the ECM. Press and hold the switch in the LOCK position. With the switch in the LOCK position, check the resistance from contact 3 to contact 9 and to contact 29. With the switch in the LOCK position, check the resistance from contact 3 to contact 31.Expected Result:The resistances should be less than 5 Ohms on contacts 9 and 29. The resistance should be greater than 5000 Ohms on contact 31.Results: Below is an image of the switch wiring to the ECM.OK - The resistances are correct.Repair: The ECM is very unlikely to have failed. Reconnect all connections and visually inspect the wire harness. Check for any active diagnostic codes and check the auxiliary hydraulics for proper operation. Perform the Test Steps again and verify all results.Replace the ECM, if the problem is occurring after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".Stop. NOT OK - The resistances are not less than 5 Ohms on either contact 9 or contact 29 or the resistance is not greater than 5000 Ohms on contact 31.Repair: The circuit is shorted or the circuit has an open in the wire harness or in a connector. Locate the problem. Repair the wire harness or the connector or replace the wire harness or the connector.Stop.
Expert:  catmastertech replied 1 year ago.
Here is a different testing guide that covers the rest of the circuit.Test Step 1. CHECK FOR THE INSTALLATION OF THE QUICK COUPLER Turn the key start switch to the "ON" position. Open the "Service" menu in the Caterpillar ET.Expected Result:The status of the quick coupler should be displaying "INSTALLED".Results: OK - The quick coupler is installed. Proceed to Test Step 2. NOT OK - The quick coupler is not installed.Repair: Click on the status of the quick coupler and select the installed option.Stop.Test Step 2. CHECK FOR PROPER OPERATION Clear the diagnostic codes from the "Logged Diag. Codes" screen on the Caterpillar ET. Place the lever of the ball valve which is located on the integrated toolcarrier in the horizontal position. Run the machine. Press the quick coupler switch to the LOCK position and then press the quick coupler switch to the UNLOCK position. Perform this step several times. Turn the key start switch to the OFF position.Expected Result:The quick coupler pins should have extended and the quick coupler pins should have retracted.Results: OK - The quick coupler pins actuated in both directions.Repair: There is no problem at this time. Check for any diagnostic codes in the logged file.Stop. NOT OK - The quick coupler pins did not actuate in one or both directions. Proceed to Test Step 3.Test Step 3. CHECK FOR PROPER STATUS WITH THE SWITCH IN THE "LOCK" POSITION. Turn the key start switch to the ON position. Monitor the "Status" screen on the Caterpillar ET. Depress the switch in the "LOCK" position.Expected Result:The following list describes the status of the components that should be displayed on the Caterpillar ET: The "quick coupler switch" should display "Engaged". The "quick coupler pin" should display "Engaged". The "quick coupler solenoid" should display "On". The "Auxiliary Hydraulics Sol #2" should display "1.06 Amps" approximately. Results: OK - The status of the components are correct. Proceed to Test Step 4. NOT OK - The status of the "Quick Coupler Switch" remained in the "Off" status.Repair: See Troubleshooting, "Switch (Quick Coupler)".Stop. NOT OK - The status of the "Quick Coupler Switch" displays "Engaged". The status of the "Auxiliary Hydraulics Sol #2" is not displaying "1.06 Amps" approximately and the "quick coupler solenoid" is not displaying "On". Proceed to Test Step 5. NOT OK - The status of the "Quick Coupler Switch" displays "Engaged". The status of the "Auxiliary Hydraulics Sol #2" is not displaying "1.06 Amps" approximately or the "quick coupler solenoid" is not displaying "On".Repair: The ECM is very unlikely to have failed. Reconnect all connections and visually inspect the wire harness. Check for any diagnostic codes in the logged file. Verify that the problem still exists. If the problem still exists perform the Test Steps again.Replace the ECM, if the cause of the problem was not found after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".Stop.Test Step 4. CHECK FOR PROPER STATUS WITH THE SWITCH IN THE "UNLOCK" POSITION. Monitor the "Status" screen on the Caterpillar ET. Depress the switch in the "UNLOCK" position.Expected Result:The following list describes the status of the components: The "quick coupler switch" should display "Disengaged". The "quick coupler pin" should display "Disengaged". The "quick coupler solenoid" should display "On". The "auxiliary Hydraulics sol #1" should display "1.06 Amps" approximately. Results: OK - The status of the components are correct.Repair: Check the "Logged Diag. Codes" screen for any diagnostic codes that may have occurred during the Test Steps. If no diagnostic codes exist, the problem does not appear to be electrical. See Testing and Adjusting, RENR3584.Stop. NOT OK - The status of the "Quick Coupler Switch" remained in the "Off" status.Repair: See Troubleshooting, "Switch (Quick Coupler)".Stop. NOT OK - The status of the "Quick Coupler Switch" displays "Engaged". The status of the "Auxiliary Hydraulics Sol #1" does not display "1.06 Amps" approximately and the "quick coupler solenoid" does not display "On". Proceed to Test Step 5. NOT OK - The status of the "Quick Coupler Switch" displays "Engaged". The status of the "Auxiliary Hydraulics Sol #1" does not display "1.06 Amps" approximately or the "quick coupler solenoid" does not display "On".Repair: The ECM is very unlikely to have failed. Reconnect all connections and visually inspect the wire harness. Check for any diagnostic codes in the logged file. Verify that the problem still exists. If the problem still exists perform the Test Steps again.Replace the ECM, if the cause of the problem was not found after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".Stop.Test Step 5. CHECK THE AUXILIARY CONTROL Check the status of the Auxiliary Control on the Caterpillar ET.Expected Result:The status of the "Auxiliary Hydraulics Lever" should be displaying a constant "0%".Results: Below is the wiring of the circuit. OK - The status of the "Auxiliary Hydraulics Lever" is displaying a constant "0%".Repair: The ECM is very unlikely to have failed. Reconnect all connections and visually inspect the wire harness. Check for any diagnostic codes in the logged file. Verify that the problem still exists. If the problem still exists perform the Test Steps again.Replace the ECM, if the cause of the problem was not found after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".Stop. NOT OK - The status of the "Auxiliary Hydraulics Lever" is not displaying a constant "0%".Repair: See Troubleshooting, "Auxiliary Hydraulics does not function".Stop.
Expert:  catmastertech replied 1 year ago.
I know you will not be able to do the steps that require ET but, just wanted you to see what else may be involved to find the problem.Please understand, all contact is limited to this site per policy. Also do not post personal information as the site is open to the public and anyone can see your information.
Expert:  catmastertech replied 1 year ago.
Are you certain the fuse that fails is P7? I see that as the dash gauges power fuse but, not related to the quick coupler fuse.Or did I misunderstand you issue is with the bucket quick coupler switch?If you can take pictures of the fuse and switch you are having issues with and I will check again. (if this is not the quick coupler, the above information is wrong)

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