Old tractor and battery terminals

Constantan wire for stable current shunts can be salvaged from type J, T and E thermocouples.

DC clamp-on ammeters are cheaper than replacing the vehicle electronics. This one can handle from milliAmp parasitic drain to 100A charging current, but not starter current, even on my riding mower. The 400A DC clamp-on probe I use to measure that is no longer available.

These can show that the charging system is alive, at least:

-jsw

A very sizeable percentage odf staters today draw less than 100 amps (permanent magnet geared starters aften draw 75 amps or less)

Given the fact that the indicator I used was the vertical needle on an aircraft instrument landing cross-needle indicator, with no real calibrated scale, I wasn't that worried about stability. about 8" of 16 Ga tinned stranded copper wire was sufficient for my purposes. :-) Reasonable deflection at normal loads.

But I will remember that for future use. Thanks.

Enjoy, DoN.

(Um, why would it kill an alternator?) This is a 9N tractor thread. She ain't got no alternativenator.

Granted, my wrench work ended back in the mid-80s, so it is a teensy bit dated. It was aimed at EMP-proof vehicles, though.

- The list of Obama administration disappointments would take three rolls of toilet paper to record. --BMF

The only thing (OK, 2 things) I ever thought were a good idea about the old VW bugs were 1) the ankle-straps in the back seat, which most silly people used as sissy handles. and 2) the front seats pivoted from the front.

That was so thoughtful of them, and gave us couples much more room.

Because the girl I dated (and I) were much lighter than yours, we never caught her seats on fire. Back then, though, I smoked after sex. (Yes, I checked.)

- The list of Obama administration disappointments would take three rolls of toilet paper to record. --BMF

An alternator system can throw a pretty good voltage spike on dump - enough to take out the ECM, and sometimes the diodes in the alternator - as well as possibly the regulator

That's your fault, Don. You should have had the shunt in the ground side.

As for SU fuel pumps, they were designed to save fuel. The car on the side of theroad uses none....

Well ... the ground connection was from the battery to the chassis, and included the starter current. What I was metering were the things controlled by instrument panel switches (ignition -- *not* starter current, headlamps, instrument panel lamps, turn signals, and not much else. Those were grounded everywhere to the nearest chassis point, an d hard to put the shunt in that side without including the starter motor.

So -- it was more my fault for not protecting the shunt from moving parts of the car (e.g. the bonnet prop rod. :-)

They do that, for sure. :-)

Enjoy, DoN.

I housed a bare 100A shunt in a PVC conduit tee. The heavy current leads pass through the straight ends and the sense leads, made from in-line fuseholders, come out the center leg. The fuseholders restrain the shunt so it doesn't need mounting screws that would expose voltage on the outside.

For this particular combination the heavy current bolts also keep the shunt in place because they won't pass into the round ends.

I bought another 1.000 milliOhm 100A-rated shunt that lacked the 3/8" bolts. I couldn't find 3/8" brass bolts locally but a Diesel shop had

3/8-16 copper starter contacts that worked after I turned down the heads to accept soldered 3/8" brass nuts for the hex.

-jsw