Sep 19, 2017 - Office: (800) 440-3492 Ext. 383. Mobile: 336-215-0970. Email:
. Vinny Rivera. S
Service Bulletin Date:
September 19, 2017
Bulletin No: 09-19-2017
Model: Saf-T-Liner C2 Page: 1 of 7 Subject:
Testing Data Links
This service bulletin provides visual aids to go with Thomas Built Buses service video Service & Repair: Testing Data Links. To view the video, please visit this link: https://www.youtube.com/watch?v=ecLKqWc_lQg Please print out this bulletin to assist your understanding of the procedures described in the video. In this video and service bulletin, we'll show you how to test the 1939 data link on a Thomas Built Saf-T-Liner C2 school bus. Testing of the data link is necessary when you're troubleshooting a network problem or a module not working correctly. SAFETY WARNING - Prior to starting, apply the parking break, turn the engine off and chock the tires.
Step 1: Test Resistance First we must check the electrical resistance of the data link. To obtain an accurate reading: •
Disconnect batteries and turn ignition OFF.
•
Set multi-meter to ohms section. Ω
•
Locate diagnostic connector located under the dash.
•
Insert multi-meter probes into pins C and D.
Page: 2 of 7 Terminals C and D Test Values If reading is 60Ω ± 6Ω : Everything is normal (see slide below). Proceed to Step 2.
If reading is 120Ω ± 12Ω : One of three problems exists (see slide below).
Bulletin No: 09-19-2017
Page: 3 of 7 Terminals C and D Test Values (cont.) If reading is 40Ω ± 4Ω :
If reading is 0 - 5Ω :
Bulletin No: 09-19-2017
Page: 4 of 7
Bulletin No: 09-19-2017
Terminals C and D Test Values (cont.) If reading is > 1000Ω :
IMPORTANT! If any incorrect reading is discovered, then that problem must be corrected prior to continuing the test.
Once any detected problems have been corrected: •
Reconnect the battery.
•
Turn the ignition switch ON.
•
Proceed to Step 2: Test Voltage to test other components of the data link.
Page: 5 of 7
Bulletin No: 09-19-2017
Step 2: Test Voltage
Begin by switching your multi-meter to the DC Voltage section. •
Insert the negative (black) probe into pin A of the diagnostic connector for a ground.
•
Insert the positive (red) probe into pin B.
•
This will show the current battery voltage. Reading should be ± 12.5v in order to continue.
Page: 6 of 7 Step 2: Test Voltage (cont.) • • •
Connect the positive (red) probe in pin C. Connect the negative (black) probe in pin A (the ground). The reading should be in the following range:
• • • •
Keep the negative (black) probe in pin A (the ground). Move the positive (red) probe to pin D. The reading should now be in the range shown below. If the readings are in this range, then the modules are working properly.
Bulletin No: 09-19-2017
Page: 7 of 7
Bulletin No: 09-19-2017
Step 2: Test Voltage (cont.) If the reading is greater than the range, then you have a module that is shorted to power internally.
Got questions or want more information about testing the data link in a Thomas Saf-T-Liner C2 bus? Give us a call. Office: (800) 440-3492 Ext. 383 Mobile: 336-215-0970 Email:
[email protected] Vinny Rivera Service & Training Manager
Carolina Thomas, LLC | 6327 Burnt Poplar Road | Greensboro, NC 27409 | (800) 440-3492 | CarolinaThomas.com
