Joined: Apr 23, 2008 Posts: 92 Location: Kansas City
Posted: Sat Aug 20, 2016 11:36 am Post subject: M38 Ammeter
I have an M38 with an AC1501244 ammeter installed and can't seem to get any movement out of it. Here is what I've done:
Checked charging voltage at batteries- 27 volts revving the motor slightly.
Voltage not running on wire 8 and 9 on the back of the ammeter- 25 volts.
Voltage running on wire 8 and 9 back of ammeter- 27 volts.
I took that gauge and installed it on my M38A1 and it shows a charge right after the vehicle starts then goes back to center. So I checked the same voltages on the M38A1, and here is what I found:
Charging voltage at the batteries running revving slightly- 30 volts.
Voltage on wire 8 & 9 on back of ammeter- 25 volts.
Voltage running on wire 8 & 9 back of ammeter- 30 volts.
What voltage should I be seeing some movement on the ammeter or should I be checking ammperage? _________________ Bill
GP, GPA, GPW, M38, M38A1
Bantam T-3, M100
MVPA #1196
It is an amp meter Bill. What you see on 8 & 9 depends on the batteries' state of charge and the output/RPM of the generator. In your examples the M38 is had nearly fully charged batteries and at a 2 volt spread across the shunt in the voltage regulator probably won't show much needle movement. On your A1 you had a 5 volt spread which obviously resulted in more meter movement.
Did you use the TB 9-2300-228-20 during your troubleshooting? I don't see any posting of the static (eng off) readings for 8 & 9 when disconnected from the amp meter..
I have a great distaste for amp meters. They only give you half an answer while the voltmeter gives you both halves of the answer. I run volt meters on all my military stuff. Dead end 8 & 9 and ground volt meter to firewall and take volt meter plus to the #27 spider. And be "Happy for the rest of your life"! _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Apr 23, 2008 Posts: 92 Location: Kansas City
Posted: Sun Aug 21, 2016 6:18 am Post subject:
Wes thanks for the reply. I used the M series gauge trouble shooting guide that I have seen. The static voltages, (eng off), were the first readings of 25 volts. I think I have 1 volt meter in my spare parts. I'll have to give it a try. I'll review the troubleshooting in the referenced TB. Thank you. _________________ Bill
GP, GPA, GPW, M38, M38A1
Bantam T-3, M100
MVPA #1196
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