Drain is on the circuit card, or inside the genset? Circuit card, suspect the caps first, diodes next, other semiconductors last.

--johnny

On Mar 18, 2016, at 5:22 PM, Matt Colie wrote:

> It was the voltage regulator. It tests as good by Presolite's diagnostic, but it was the problem. Multiple megohms in every direction at Fluke 77 test voltage, but put it in the circuit and it wanted to draw ~ 25ma.

Hi Matt,

Your mention of the Fluke's "test voltage" is a key fact. Meters such as the venerable Simpson 260 that were in use at the time the Onan was designed put a small but non-trivial amount of DC bias across their leads when in resistance mode and in some cases this was enough to "power up" a device under test. Modern DVMs don't put anywhere near that amount of bias on their leads and therefore may give different indications compared to the older meters.

This difference between the meters' principle of operation must be understood when interpreting displayed results and those who put their unlimited trust in the readout of their DVM may be fooling themselves unless they understand this distinction.

Another classic case is a DVM measuring perfect +12V downstream of a corroded battery terminal whereas an older meter (which placed more load across its leads due to its method of operation) would have read 0V. I've seen this case many times.

--Jim
1977 Eleganza II
1977 Royale
Hamilton,

I keep 77 as main tool and some cheaper analogue meters because they are, well, analogue. Matt cant you just add a combiner between house and garden tractor battery as a cheap viable fix?