stubuzz Posted July 11, 2023 Share Posted July 11, 2023 To troubleshoot my alternator I need to read the signals sent to and from the ECU to the smart charge regulator. These are 0-5v dc square wave signals. Now, the troubleshooting guide says that an oscilloscope is needed. However, can I get a reading with a digital volt meter? I would give it a try, but the car is not running at the moment as a I am waiting for parts on back order. (Ford Thailand!) Link to comment Share on other sites More sharing options...
OneMoreFarang Posted July 11, 2023 Share Posted July 11, 2023 You should be able to see with a multimeter if there is any voltage/signal at all. I.e. with a broken cable there would be nothing. But that's about it. Multimeters have a different purpose. Link to comment Share on other sites More sharing options...
stubuzz Posted July 11, 2023 Author Share Posted July 11, 2023 6 minutes ago, OneMoreFarang said: You should be able to see with a multimeter if there is any voltage/signal at all. Yes, I need to see that the ECU is is sending a voltage signal. Link to comment Share on other sites More sharing options...
OneMoreFarang Posted July 11, 2023 Share Posted July 11, 2023 2 minutes ago, stubuzz said: Yes, I need to see that the ECU is is sending a voltage signal. With the multimeter you should be able to see that is sends a voltage signal. But the signal can obviously be "wrong". And that is what you don't see with a multimeter. Link to comment Share on other sites More sharing options...
stubuzz Posted July 11, 2023 Author Share Posted July 11, 2023 4 minutes ago, OneMoreFarang said: But the signal can obviously be "wrong". And that is what you don't see with a multimeter. Thanks. The square wave is a % duty cycle and that is what the alternator uses to determine the output charging rate. I don't really want to but a oscilloscope to diagnose this problem. Link to comment Share on other sites More sharing options...
digbeth Posted July 11, 2023 Share Posted July 11, 2023 an analog meter might be able to see the fluctuation between the +5 and -5v of a square wave Link to comment Share on other sites More sharing options...
bluejets Posted July 14, 2023 Share Posted July 14, 2023 (edited) On 7/11/2023 at 8:58 PM, stubuzz said: These are 0-5v dc square wave signals. No, multimeter will tell you nothing. There is a small scope available for less than $40. They work well, have used one here since the flood took out my other bench unit. So well in fact I've never got around to replacing the former at all. DSO150............ https://www.ebay.com.au/itm/385688686532 Mine gets used quite a lot so the only modification I did was to add a LiPo battery and usb charger. There are online youtube videos on "how to use" and suggest a quick look at a couple of those as well. Cheers. Edited July 14, 2023 by bluejets Link to comment Share on other sites More sharing options...
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