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Thomas Ford 85-16
Top Member
USA
4177 Posts |
 Posted - 02/26/2019 : 7:21:24 PM
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I searched the forum, and I think this thread (http://www.schoolbusfleet.com/forum/topic.asp?TOPIC_ID=24052&SearchTerms=b7,alarm) gets close, but not quite my problem.
Problem:
2003 Blue Bird GMC Conventional, CAT 3126, Allison 2000 and air brakes. Alternator was fading in and out, so I replaced it before it stranded anyone. Since I can only work on these late at night, I got a Wilson branded alternator from O'Reilly Auto. They do a good job finding parts for these. Unfortunately now the tachometer does not work. I really think I would have noticed this when I tested after installation, but it's possible I missed it. So I do not know if it ever worked with the alternator, or if it stopped. Is the two wire connection on the side of the alternator the signal for tach? Does anyone have a wiring diagram they can share? Everything was a direct transfer for wiring but tach still isn't working.
Another problem noticed on this bus is that the low air and low oil pressure alarms are not working properly. Since the driver did not report it, I do not know if it is a new problem since the alternator, or something that had been happening before. Typically when you key these on, the low oil alarm would pulse, and it would go constant if low air kicked in. Air overrode oil. That still works with key on and engine off. Now though, when the engine is running, the low air alarm (constant) will not sound. Lights come on, but alarm will not sound if engine running. I don't know about low oil pulsing alarm because the engine has good oil pressure (thank goodness). Are there any schematics on this available so I can start diagnosing? Has anyone seen this behavior on the multi-function alarms before?
Thanks in advance for your ideas! |
Edited by - Thomas Ford 85-16 on 02/26/2019 7:53:10 PM
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GMC/Chevy B7, alarm and tach
