Fluke fl323 multi meter issues

[The motor guy]

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.

You're the first person to say that. Everywhere on the internet says excess ac noise from the alternator will burn up the ecm, pcm, and the module on the vp44

 

[Dave Sherman]

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

Quite normal. You're connecting to a DC voltage from zero volts, which creates a change in voltage that carries through the RMS converter as a change in voltage, so you'll briefly register an AC voltage. If it's reading zero (or close to it) while it's connected, then your AC ripple is very low. Worked for Keithley Instruments for 17 years as an applications engineer for the first couple of years, then as a design engineer.

 

[clinebarger]

Automotive controllers are pretty robust, Though Mopar had a reputation for cracked solder joints.

Many Modules are replaced for no reason, Justifying it after the fact by finding excessive A/C Ripple doesn't prove anything.

 

[The motor guy]

Automotive controllers are pretty robust, Though Mopar had a reputation for cracked solder joints.

Many Modules are replaced for no reason, Justifying it after the fact by finding excessive A/C Ripple doesn't prove anything.

The ecm was messed up. I sent it off for repair The wait to start light was slow to come up, which basically means the ecm was slow to boot up and you couldnt start the truck until that light came on and went out. It's fixed now although I don't know what they did. Probably replaced a diode or something.

 

[The motor guy]

So even if you have ac ripple from a bad diode in the alternator the ecm and pcm won't even care?

 

[The motor guy]

Clinebarger, maybe this is just another internet wives tale I'm worried about. The ecm I pulled off was the original numbers matching the engine from 1999, so it makes you wonder. Although the ac ripple isn't a concern until the alternator goes bad.

 

[The motor guy]

Quite normal. You're connecting to a DC voltage from zero volts, which creates a change in voltage that carries through the RMS converter as a change in voltage, so you'll briefly register an AC voltage. If it's reading zero (or close to it) while it's connected, then your AC ripple is very low. Worked for Keithley Instruments for 17 years as an applications engineer for the first couple of years, then as a design engineer.

Good to know. Yeah even though it's a fluke brand, I guess it's pretty low on their quality scale. I also tested the apps voltage on the dc setting and that time it started low, then worked its way up to .6 so any other meter would have said .6xx.
Is there a reason why the ac setting starts high then goes down and the DC setting starts low and goes up?

 

[clinebarger]

So even if you have ac ripple from a bad diode in the alternator the ecm and pcm won't even care?

Ripple can cause interference....Especially with Sine Wave producing sensors, If you have ripple, Replace the alternator!

 

[The motor guy]

Ripple can cause interference....Especially with Sine Wave producing sensors, If you have ripple, Replace the alternator!

As stated above I couldn't get a reading on my meter, so I think it's fine. The meter went to 0

 

[The motor guy]

Quite normal. You're connecting to a DC voltage from zero volts, which creates a change in voltage that carries through the RMS converter as a change in voltage, so you'll briefly register an AC voltage. If it's reading zero (or close to it) while it's connected, then your AC ripple is very low. Worked for Keithley Instruments for 17 years as an applications engineer for the first couple of years, then as a design engineer.

Dave, how come my fluke meter only shows like two digits? It's will show .60 when all these people with multi meters on YouTube will show the third digit such as .628 for example.