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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.
Fluke fl323 multi meter issues
- Thread starter The motor guy
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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.
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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
Reading zero is normal if there is no AC at all.
The test is to put one lead on the + of the battery and one on the - of the battery, like you're measuring battery voltage, but set the meter on AC volts instead of DC. With the engine not running it should read 0. With the engine running you're likely to read some small voltage. I think that 0.10 volts is typically considered the threshold for failing.
The test is to put one lead on the + of the battery and one on the - of the battery, like you're measuring battery voltage, but set the meter on AC volts instead of DC. With the engine not running it should read 0. With the engine running you're likely to read some small voltage. I think that 0.10 volts is typically considered the threshold for failing.
What makes you think the alternator is electrically noisy?
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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 later
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Ecm went bad. Just got it back, so wanted to check. Seems very common on these 5.9 2nd gen dodge cummins diesels
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I'd think the multi meter would read something though. How come it zeros out?
No AC signal then. Or it is at a frequency above or below its cutoffs.
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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.
I was under the impression that you were measuring AC voltage? that is what I'd be doing, to look for problems with the alternator (bad diode). Alternator is going to have some AC component to it, it's not a generator, but it's a high DC output (the rectifiers are going to chop the AC into quasi-DC).
Anyhow. If you are using it as a clamp-on meter, it is indicating a resolution of 0.1A. I'm not crazy about how it is indicating accuracy, I much prefer when things give it as +/-gain +/-offset, I'm not sure +/-5 digits means... +/-0.5A? on top of +/-2%? (plus a 2% positional error). Anyhow--not sure I'd see much as an AC clamp on meter on an alternator, would have to think about it (it's pulses of current out, never back (hopefully!), which will make for an AC signal, but rich in harmonics).
Anyhow. If you are using it as a clamp-on meter, it is indicating a resolution of 0.1A. I'm not crazy about how it is indicating accuracy, I much prefer when things give it as +/-gain +/-offset, I'm not sure +/-5 digits means... +/-0.5A? on top of +/-2%? (plus a 2% positional error). Anyhow--not sure I'd see much as an AC clamp on meter on an alternator, would have to think about it (it's pulses of current out, never back (hopefully!), which will make for an AC signal, but rich in harmonics).
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The clamp portion only works on AC I think. It may not work at all honestly. I've never gotten it to read using that clamp portion.
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Does it read voltage or just ac amperage? Maybe that's why it zeroed out. I was using the leads
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.
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I see. Yeah I bought this thing off ebay before realizing all this bs. Also I need a single wire for the clamp portion to work. Doesn't work when you put it around the hot, neutral, and ground at the same time. Sounds like it's not even accurate enough to measure what I'm trying to measure. It's my understand it needs to be less than .05vac It's possible I had it on the amp setting when I tried earlier
I 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.
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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 vp44
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