Re: 340U Starting system Woes

Posted by Paul in MN on February 17, 2006 at 19:34:08 from (71.36.128.82):

In Reply to: 340U Starting system Woes posted by DC-TX on February 17, 2006 at 08:36:01:

DC

From the description of what you have wired on the 2 voltmeter posts, I do not see how the tractor even starts or runs. I think that you have confused the wiring needed for the ammeter with what is needed for the voltmeter. They are not directly interchangable. The 340 was originally wired with an ammeter and that system worked well for almost 50 years on your tractor. I think that your simplest solution is to buy an ammeter and put it in instead of the voltmeter. The discussion of which is better is just an academic discussion that can be understood by electrical "experts". I think that you will solve a lot of the problems just by putting in the ammeter back in that hole in the dashboard and wire it up with the same wires on each terminal that you have transferred to the voltmeter. But when you do this, GET RID OF THAT WIRE FROM THE AMMETER NEG TO GROUND, or maybe it will burn itself up along with a few other wires.

A correctly wired voltmeter will be hooked up from a battery + (on one terminal of voltmeter) to ground (on the other terminal of voltmeter), in which case it will read volts all the time (some GM cars did this about 15 years ago)...., or.... from the switched side of the ignition switch to one voltmeter terminal(+) and then to ground from the other terminal.

Your tractor used the ammeter terminals as junction block terminals, thus so many wires under each screw. The ammeter has almost 0 ohms resistance, so it acts like a heavy wire conducting all of the electricity for the tractor. Versus a voltmeter which has a high internal resistance, and conducts almost no electricity at all. Your tractor needs the ammeter, unless you understand how to rewire the dashboard wires to eliminate it.

P.S. I taught physics for 32 years, and a lot of the kids would screw up on interchanging the voltmeter and ammeter. Before we bought Fluke meters (with internal fuses) we expected to burn up a few ammeters every year. They are destroyed in a fraction of a second. I checked everyone's circuit before powering it up to minimize the loss of meters. The rule was "you burn it, you buy it, I burn it, I buy it." They learned well, but were sure happy to have me check their circuits before plugging them in.

I have a 340U and have fought with the dash and ammeter, I know that it is not easy. Disconnect the battery when you are working under the dash.

Paul in MN

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