Good Sam Club Open Roads Forum: Truck Campers: Generator start leads
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deltabravo

Spokane, WA

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Posted: 10/13/21 06:51pm Link  |  Quote  |  Print  |  Notify Moderator

MT BOB wrote:

A Fluke 33 cannot measure DC amps, without using a DC current clamp add on.

...which he has.... see original post.

memilanuk wrote:

My clamp-on ammeter shows 350-375 amps draw - for about a second or two.



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memilanuk

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Posted: 10/13/21 08:57pm Link  |  Quote  |  Print  |  Notify Moderator

My mistake... it's a 36, not a 33. And yes, it's a clamp-on ammeter and yes, it does DC current as well as AC.

MT BOB

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Posted: 10/14/21 07:26am Link  |  Quote  |  Print  |  Notify Moderator

memilanuk wrote:

My mistake... it's a 36, not a 33. And yes, it's a clamp-on ammeter and yes, it does DC current as well as AC.


Yes, big difference between the 2 meters. Perhaps try the zero set procedure, then test.
They sell inline battery cable circuit breakers, up to 300A. I have them on mine, as they also work well as switches.
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MT BOB

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Posted: 10/14/21 07:27am Link  |  Quote  |  Print  |  Notify Moderator

deltabravo ..which he has.... see original post.

Perhaps you should sharpen up your reading comprehension skills, and your knowledge of Fluke meters.

deltabravo

Spokane, WA

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Posted: 10/14/21 07:07pm Link  |  Quote  |  Print  |  Notify Moderator

MT BOB wrote:

deltabravo ..which he has.... see original post.

Perhaps you should sharpen up your reading comprehension skills, and your knowledge of Fluke meters.


He said he has a clamp on meter.

Perhaps you should learn how to quote posts correctly.

JoeChiOhki

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Posted: 10/14/21 07:42pm Link  |  Quote  |  Print  |  Notify Moderator

HMS Beagle wrote:

I'm a bit surprised by your measurement of 375A - even momentary - to start a small genset. I wonder if is it an artifact of the sampling rate of the clamp ammeter. A Cummins 5.9L diesel draws only about 300A cranking, motorcycle engines in the 1000 - 1200cc range draw around 150A at stall and 100A cranking. These measured with a 100 KHz amp probe on a 1Ghz recording O'scope. Even if it peaks at 375A for a few milliseconds, that would not heat a thermal fuse enough to blow it.

You might try shutting the fuel off or removing the spark wire from the genset, crank for several seconds and see what the starter really draws. 375A @ 12V = about 6 HP!


Yeah, that sounds like a crazy amount of juice...... My 4000 watt Champion which is an electric start from a tiny battery only has #8 wire so I know it can't be sucking near that much juice for something that's similar or smaller of an engine.....

I would think 37.5 amps would be more realistic...


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memilanuk

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Posted: 10/15/21 11:51am Link  |  Quote  |  Print  |  Notify Moderator

Well, until someone else actually puts a meter on the start leads a similar Onan 2500 LP generator...

[image]

[image]

Got everything back together, started the generator with the meter clamped on one of the start leads. Let it run about 15-20 minutes, then shut it down. Pulled it out, took the first pick, cleared the MAX hold, set it again, and about 15 minutes later, started it again.

ticki2

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Posted: 10/15/21 03:05pm Link  |  Quote  |  Print  |  Notify Moderator

Is the shadow on the screen hiding a decimal ?


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MT BOB

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Posted: 10/15/21 04:06pm Link  |  Quote  |  Print  |  Notify Moderator

Well,a 4k onan starter draws 100-145 amps.Could not find the specs for yours.
BUT, the proper way to check starter draw is-- disabling the fuel or ignition, and continuous cranking. Same as with an auto, although newer automotive testers are calibrated to ignore the "inrush" current. What you might have is a meter too sensitive for the job, and it might even be "seeing" that much current, but only for a millisecond. Try the meter on your truck.

memilanuk

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Posted: 10/15/21 04:13pm Link  |  Quote  |  Print  |  Notify Moderator

ticki2 wrote:

Is the shadow on the screen hiding a decimal ?


On the 1000A DC scale there is no decimal point.

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