Using your ammeter as a jumper wire?!?!

So I just finished watching one of Paul's older videos on a 95 Buick lesabre with a P1406 EGR code. He used his dmm set to amps to jump the ground side control to activate the EGR valve!! I thought this was absolutely brilliant!! This is the first time I've ever seen this. Not that I have a whole lot of experience with electrical/electronic diagnosis. My question though is that when he did this he back probed the control wire, wouldn't this be hooking your ammeter up in parallel? I was always taught that doing this will always blow the fuse in the meter. How is this possible? What other circuits can you use this on? Is there any advice or things needed to be taken into consideration when doing this? This is definitely something I want to add to my bag of tricks!

Wood wrote: My question though is that when he did this he back probed the control wire, wouldn't this be hooking your ammeter up in parallel?

No. The red lead of the DMM is connected to the GROUND side of the circuit. It is reading 12 volts because the ground side switch is open.

The ammeter is in SERIES with the GROUND side of the circuit.

Ok! I think I understand what you're saying. So it would be in parallel if the driver circuit was being grounded (obviously if it was there would be no need to jumper it) but since it is essentially open from not being commanded on by the computer then your meter becomes the series connection to ground. Thank you for clearing this up for me.

Wood wrote: So it would be in parallel if the driver circuit was being grounded

No. It would be in parallel if one lead was on the POSITIVE side of the circuit, and the other lead was on the NEGATIVE side of the circuit.

since it is essentially open from not being commanded on by the computer then your meter becomes the series connection to ground. Thank you for clearing this up for me.

Yes. The Ground side was open. The ammeter leads Connected the GROUND side of the circuit to a GROUND.

Not trying to stir the pot here but what you said is incorrect. Saying that your meter can only be in parallel if it is hooked up with the positive on one side of the circuit and the negative on the other side of the circuit is absolutely false. You can easily hook your meter in parallel with both leads on either side of the circuit. With that logic you would need an individual wire for each load going back to the source and ground. Parallel just means having multiple paths to flow current through. But you drawing out that the driver circuit is open and therefore cuts that path for current flow, making the ammeter the only path to ground, helped in understanding the diagnostic method.

The guiding rule with using ammeters is they always connected In the circuit and Not Across the circuit, but even connected correctly the pitfall exist of the current being high enough to blow the fuse. There are a couple of work arounds to prevent the chance of the fuse blowing.

The one Paul has used in couple of videos is a self-restting solid state PPTC fuse between the meter and the circuit As most DMM are fused at 10amp choose lower value PPTC device






An alternative for low current circuits I was taught by my High School Physics Teacher is to use a bulb in series with the meter.

Awesome! I didn't even think of that. Those PPTC fuses look pretty cool, I'll have to get some of those to mess around with.

Not sure what else I can add here. You guys are all so awesome. pole71, thanks for taking the time to even draw on a screen shot to help another in this awesome community. I also wanted to speak to you personally and thank you for the work you were doing on adding time stamps on my Verus series. I really didn't mean to take the wind out of your sails in being very specific in what I was looking for. I hope I didn't offend you. I value your presence here so much. It is very obvious to me how much you help out.
And to the rest of you guys here. I am so grateful for all of you. I am honored by how my community talks and interacts with each other. Have a blessed day.

Always good to hear from the man himself! Paul I just wanted to reach out to you and personally thank you. I just took my A6 electrical and A8 engine performance ASEs and I passed them with flying colors. I owe it all to your book and all the great content you post on YouTube. From a new mechanic in the industry I'm already making giant strides all thanks to you.

This has already helped me twice. it seems I am learning something new every day. Can't wait to get home from work to watch more videos.