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DSeries4 
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Joined: 12 Sep 2009
Location: Ontario, Canada
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 Topic: Bad ammeter?
Posted: 10 Aug 2026 at 1:59pm |
Put a new wiring harness and gauges in my D15 diesel. Everything seems to be hooked up properly. However, the ammeter does not like to move. Does not move (charge or discharge) when I turn on the lights and/or trigger the manifold heater. The only time it did move was when I flashed the generator - went over to charge and then returned to zero.
Have not had the engine running yet. I want to get any gremlins behind the dash sorted out before putting the fuel tank back on.
If it's not the ammeter, what else could it be? I do have 12+ volts on both terminals of the gauge.
Appreciate any assistance!
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'49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '63 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
Points: 1891
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Posted: 10 Aug 2026 at 3:27pm |
The wiring diagram I have for the gasoline D15 shows that the ammeter is not in the circuit for the lights, and I suspect that the diesel pre-heater is also not connected through the ammeter.
Since you did get meter movement previously then the meter is probably good.
Edit: The lighting circuit is connected to the "L" terminal on the voltage regulator, you could probably use an ohmmeter to verify if the manifold heater is also connected there, which I suspect it is.
Edited by Les Kerf - 10 Aug 2026 at 3:33pm
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 93063
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Posted: 10 Aug 2026 at 3:54pm |
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there is a HOT WIRE on the starter that feeds the amp meter... where does the wire on the OTHER SIDE of the amp meter go ???? If you have an "L" terminal, that explains it... If it runs to a common FEED TERMINAL for the tractor, thats another problem..
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Like them all, but love the "B"s.
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DSeries4
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Joined: 12 Sep 2009
Location: Ontario, Canada
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Posted: 11 Aug 2026 at 3:16pm |
 steve(ill) wrote:
there is a HOT WIRE on the starter that feeds the amp meter... where does the wire on the OTHER SIDE of the amp meter go ???? If you have an "L" terminal, that explains it... If it runs to a common FEED TERMINAL for the tractor, thats another problem.. |
The original wiring harness only had one wire going to the voltage regulator - the one for BAT. The L terminal was not used. I don't have the wiring diagram from the manual with me now, but I was pretty sure I had wired it correctly. Can't remember where the ammeter connections go at the moment.
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'49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '63 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080
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Les Kerf
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Posted: 11 Aug 2026 at 3:34pm |
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Is this a ready-made wiring harness that you purchased? I am working under the assumption that you installed a new harness that duplicates the factory connections, if so, the ammeter will not register current draw from the lights according to the only diagram I have.
Edited by Les Kerf - 11 Aug 2026 at 3:36pm
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steve(ill)
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Location: illinois
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Posted: 11 Aug 2026 at 4:52pm |
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Like them all, but love the "B"s.
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steve(ill)
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Location: illinois
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Posted: 11 Aug 2026 at 5:32pm |
i thought the point of the "L" terminal on the regulator was to OPEN when the tractor is RUNNING.. and the "L" gets is power from the Generator... When the tractor is OFF, the contact is CLOSED and the "L" should get power from the "B" or battery... So when not running, your LIGHTS should show on the amp meter.... Your missing a wire or two..
What does power the light switch ???.. wire #7 above...
Edited by steve(ill) - 11 Aug 2026 at 5:34pm
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Like them all, but love the "B"s.
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
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Posted: 11 Aug 2026 at 5:38pm |
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the HEATER needs the starter switch on to get power to the SOLENOID, which then gets BATTERY power to the heater... not thru the amp meter.
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Like them all, but love the "B"s.
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
Points: 1891
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Posted: 11 Aug 2026 at 6:35pm |
steve(ill) wrote:
i thought the point of the "L" terminal on the regulator was to OPEN when the tractor is RUNNING.. and the "L" gets is power from the Generator... When the tractor is OFF, the contact is CLOSED and the "L" should get power from the "B" or battery... So when not running, your LIGHTS should show on the amp meter.... |
Thank you for that clarification Steve 
That is the problem with this type of inferior wiring diagram, they are incomplete. A proper schematic will show the internal connections of the regulator, from which a proper diagnosis can be made.
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