Tach reading low
Not sure where the problem lies. 2002 Itasca Horison, Cummins 300 HP 5.9 ISB, Allison 6 speed transd, Freightliner chassis Normally at 60 MPH the tach reads about 1700-1800 rpm. Noticed yeste...
Forum Discussion
I'm fairly sure you have what Freightliner calls system III wiring for your instruments. The Vehicle Data Computer consolidates info from the engine computer and transmission computer, measures air pressures, and feeds all the data down the chassis data bus to the light bar message center on the dash. From the light bar, there is a spider harness furnishing all data to all gauges, with each gauge selecting the data required for that gauge.
Go to this link and download service bulletin 54-12.
Freightliner SB 54-12
The 54-12 service bulletin has troubleshooting information.
With your related air gauge problem, you may have bad solder joints in the VDC.
There is a repair procedure in the files section of IRV2. Go to the link below and download VDU/VDC repair.
IRV2 files section
After you download the document, read it and see if your symptoms match with what is described.
Good luck
If all else fails, 1 800 FTL-HELP is the phone for Freightliner free help desk. Have the last 6 digits of your VIN number available as they will ask for that info.
Fred
Go to this link and download service bulletin 54-12.
Freightliner SB 54-12
The 54-12 service bulletin has troubleshooting information.
With your related air gauge problem, you may have bad solder joints in the VDC.
There is a repair procedure in the files section of IRV2. Go to the link below and download VDU/VDC repair.
IRV2 files section
After you download the document, read it and see if your symptoms match with what is described.
Good luck
If all else fails, 1 800 FTL-HELP is the phone for Freightliner free help desk. Have the last 6 digits of your VIN number available as they will ask for that info.
Fred
