Alternator Clamp Test Issues


ObTechAudio

Senior VIP Member
Apr 16, 2014
452
0
Provo, UT
I'm trying to get a solid clamp test on my alternator, however, I'm getting a very funny reading that isn't making any sense (to me at least). I have two 1/0 runs and a stock run going from alt to hood battery. I'm placing my Klein CL2000 around all three runs just before the hood battery. The clamp fits around all three runs without issue. The clamp in no way remains open and is properly set to DC amperage with the correct range setting. The meter will sit around 20a until I put a heavy load on it, but even then, the meter will only rise to about 35a. I know I'm pulling much more out of it. So I clamped in the back before amp (fully knowing to only clamp until 12.8v float charge so not to tap into bank) and I pull just about 200a at 12.9v at idle - which I'm supposed to be pulling.

Any thoughts on why I cannot get an accurate reading under the hood? Am I clamping multiple runs incorrectly?

 

Massive spl

Banned
Jun 27, 2015
3,017
0
Michigan
You only need 1 run from alt to front batt. and leave the factory on there. Tom at Ohio gen said one run of wire is plenty for any alternator. Adding more then one can add extra resistance and heat and can cause problems... But yea I'd clamp one wire

 
OP
O

ObTechAudio

Senior VIP Member
Apr 16, 2014
452
0
Provo, UT
You only need 1 run from alt to front batt. and leave the factory on there. Tom at Ohio gen said one run of wire is plenty for any alternator. Adding more then one can add extra resistance and heat and can cause problems... But yea I'd clamp one wire
If wire is only rated for 250a and I have a higher amperage alt, two runs need to be used. But yes, I've clamped just 1 of the 3 and it's still very inaccurate.

 

Massive spl

Banned
Jun 27, 2015
3,017
0
Michigan
If wire is only rated for 250a and I have a higher amperage alt, two runs need to be used. But yes, I've clamped just 1 of the 3 and it's still very inaccurate.

Get better wire then. Most 1/0 is rated like 250amps for 15-20feet.... The run from alt to battery should be like 3ft if that.

 
OP
O

ObTechAudio

Senior VIP Member
Apr 16, 2014
452
0
Provo, UT
Get better wire then. Most 1/0 is rated like 250amps for 15-20feet.... The run from alt to battery should be like 3ft if that.
Negative. My particular vehicle has alt tucked under firewall near axel of the opposite side of battery. I'd say 8-10ft runs each.

 
OP
O

ObTechAudio

Senior VIP Member
Apr 16, 2014
452
0
Provo, UT
this? Amazon.com: Klein Tools CL2000 AC/DC True RMS Clamp Meter: Home Improvement
you sure you have the clamp facing the right direction? there's an arrow you must point in the direction of current flow

your low results may be accurate, try it again but have a friend rev the engine and leave peak hold off, watch it instead. alternator might just have shit output at idle
I successfully clamped in the back from bank to amp (only clamping to 12.8v so that it wouldn't hit bank). But that's only one run. I'm just trying to figure out why I can't get the meter to move at all with it in the front clamping the three runs. BTW it does ~200a at idle of 700rpm.

 

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