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- Nov 29, 2009
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- 7,293
I'm not big on electronics here, so I was trying to test for ac noise on my alternator. It shows a reading as soon as you touch the probes, then it just zeros out. What's up with it? Have it set on ac.
That's not the way to test for that. A scope would work. I would take the alternator to your parts store for testing if you have any suspicions. There should also be a filter capacitor in the circuit to filter out any AC noise riding on the DC. The capacitors often go bad (open) and dry out with age. I changed a couple before on my vehicles. They are usually fastened onto the sheet metal somewhere close to the alternator.I'm not big on electronics here, so I was trying to test for ac noise on my alternator. It shows a reading as soon as you touch the probes, then it just zeros out. What's up with it? Have it set on ac.
What makes you think the alternator is electrically noisy?Why do you say that? I see tons of techs on YouTube doing it. One on the alternator, the other on the negative post of the battery
It went up to like 1.2 once I got it connected then I guess once I held it their with a good connection it when to zero a few seconds laterThe meter registers something when you touch the probes? normal, just picking up noise and or charge from you. Touch the probes together, should get zero.
Ecm went bad. Just got it back, so wanted to check. Seems very common on these 5.9 2nd gen dodge cummins dieselsWhat makes you think the alternator is electrically noisy?
No AC signal then. Or it is at a frequency above or below its cutoffs.I'd think the multi meter would read something though. How come it zeros out?
I think it's rated at 600v so doubt it's that lol. Must be below. This fluke meter is a pos. Just doesn't show small amounts of current.No AC signal then. Or it is at a frequency above or below its cutoffs.
The '323 only does AC amperage on the clamp section. It does not measure current via the clip leads at all (or I'm missing that in the manual). It will measure DC and AC voltage via the clip leads in the respective mode.Does it read voltage or just ac amperage?
Ecm went bad. Just got it back, so wanted to check. Seems very common on these 5.9 2nd gen dodge cummins diesels
Mine was doing that too. Shop fixed a few grounds, replaced all the battery cable ends and got rid of that rid of that grey disconnect by the passenger side battery. I thought that excessive ac noise would cause all the electronics to go out. Same with the psg on the vp44I see some pretty bad A/C ripple on 2nd gen Dodge Diesels, Usually causes erratic lock-up operation by interfering with the TPS output. Can't say I've ever seen ripple knock out a ECM/PCM.