checking ground wires

[Big John]

Here you go:

http://www.ebay.com/itm/EXTECH-MN35-8-Function-Digital-Multimeter-with-FREE-temperature-probe-/131010952055?pt=LH_DefaultDomain_0&hash=item1e80dc7b77

This is a cheap DMM that will do about everything you need. The Extech stuff isn't the greatest. They aren't as accurate or robust as the equivalent Fluke, but for automotive use, they are just fine. This one even has a type K thermocouple to check temperature.

 

[A31PKG]

I've heard many times ,check the ground wire when something doesn't work . Is there a way to check wires to see if they are good other then tracing every inch to find if it is a bad ground or some other problem ?

To test a circuit on a pre-computer-controlled vehicle, all you really need is a test light. That said, a DMM is a wonderful tool. If you get one to work on your Road Runner (or similar vintage vehicle) it is most useful when measuring a thing called voltage drop. Basically: How much of the source voltage is being "dropped" (used up) by a load. Voltage drop measurements will tell you if a circuit is being "robbed" of voltage, and can also tell you on which side: power or ground. Without going into a lot of blabbering detail, here's how: Turn on the suspect circuit. Measure the voltage across the suspect load - lets say a dim light bulb - If circuit was normal, it should render you a reading of around 12 volts. This means that the source voltage (12v) is being used up or "dropped" across the load. If the bulb is dim, then the reading will be less, lets say 4 volts. Since source voltage is around 12v, then you are losing 8 volts somewhere.... At that point measure the voltage from the negative of the bulb to a good ground - preferrably the neg post of the battery - if you measure 8 volts then you've found the bad circuit. Trace & repair...simple...Right? If the reading is at or about zero, then do the same for the power side......Once you understand voltage drop, automotive electrical diagnosis is vastly easier. Good luck!

 

[Basketcase]

that's odd, my $10 Lowe's meter has a fuse

 

[Big John]

that's odd, my $10 Lowe's meter has a fuse

Good for you. I'll alert the media.

 

[Big John]

To test a circuit on a pre-computer-controlled vehicle, all you really need is a test light. That said, a DMM is a wonderful tool. If you get one to work on your Road Runner (or similar vintage vehicle) it is most useful when measuring a thing called voltage drop. Basically: How much of the source voltage is being "dropped" (used up) by a load. Voltage drop measurements will tell you if a circuit is being "robbed" of voltage, and can also tell you on which side: power or ground. Without going into a lot of blabbering detail, here's how: Turn on the suspect circuit. Measure the voltage across the suspect load - lets say a dim light bulb - If circuit was normal, it should render you a reading of around 12 volts. This means that the source voltage (12v) is being used up or "dropped" across the load. If the bulb is dim, then the reading will be less, lets say 4 volts. Since source voltage is around 12v, then you are losing 8 volts somewhere.... At that point measure the voltage from the negative of the bulb to a good ground - preferrably the neg post of the battery - if you measure 8 volts then you've found the bad circuit. Trace & repair...simple...Right? If the reading is at or about zero, then do the same for the power side......Once you understand voltage drop, automotive electrical diagnosis is vastly easier. Good luck!

:yeathat:

 

[Basketcase]

Good for you. I'll alert the media.

now that hurt......:jester:

 

[Roadcuda]

Dave, you should know better then to set yourself up around here!!!!! :lmao:

 

[69383RR]

Here you go:

http://www.ebay.com/itm/EXTECH-MN35-8-Function-Digital-Multimeter-with-FREE-temperature-probe-/131010952055?pt=LH_DefaultDomain_0&hash=item1e80dc7b77

This is a cheap DMM that will do about everything you need. The Extech stuff isn't the greatest. They aren't as accurate or robust as the equivalent Fluke, but for automotive use, they are just fine. This one even has a type K thermocouple to check temperature.

This one looks good enough for me and my needs . I really like the light stick as well .
thanks a lot to all who posted , great info !

 

[Basketcase]

Dave, you should know better then to set yourself up around here!!!!! :lmao:

well Ray needed a break, so it was my turn in the box.

 

[Jim S.]

Good for you. I'll alert the media.

And the media will report that the fuse can be found on the left side of the meter and will never blow when checking a Prius.:grumpy:

 

[Jim S.]

Nope. not those cheap ones.... The fuse was DMM itself. Chinese crap is just that... Chinese crap.

A good meter (like maybe a Fluke 87) has two fuses inside in case you do something dumb. If memory serves, 400mA and 15A fuses for most of them.

I'm not an electronics tech but I do know what I'm doing...

I actually own a Fluke 87 from years ago. I have a 20A fuse in it. I have wacked that many times working on guitar amp power supplies. Now I hook up a 100 watt light bulb in series first. (I bought some before Al Gore banned them).
Yes I have seen meters with no fuse protection at all and only rated to 5 amps.