> Hans Neureiter wrote: > On second thought, the measurement of resistance may not be so > un-significant.
Correct. We do want to know the resistance, and by measuring amps or ohms can get us there. But _I_ prefer knowing the resistance of the glow plug when is glowing - like it would when I'm using it. > A glow plug is a resistor, a electrical conductor with a > designated resistance. > Not knowing the metallurgical/chemical composition of a glow > plug element, it stands to reason to assume that the > electrical characteristics deteriorate, i.e. resistance > increases. Why would the deterioration not cause a _decrease_ in resistance? Either way, we want to identify what is good and what is not. > Ohm's law is similar to the principals of Hydraulics Correct. > A Ohmmeter tells you just the same as an Ammeter knowing the > Voltage. Almost. Based solely on ohm's law - yes. But an ohm meter can "lie" because the test environment is different than the operation environment. The wire, connections, and the glow plug can - and do - act different with 20 amps running throught them than they do with 0.2 milliamp. Add to that the margin of error when using an standard ohm meter for measurements <1 ohm. 0.6 ohms increasing to 0.9 ohms. All this to say. If you have an ohm meter - use it. A milliohm meter is better. But realize the test results may not be especially accurate. 95 ohm is clearly a failed plug. And you might be able to spot a shorted plug. But the ohm meter is not much help for anything more subtle. Thus my opening statement that the ammeter is the "preferred way to test" - not the only way. However, it is the only way I bother to test now. My test meter is just as easy to get as the ohm meter, and it's at least as easy to use, and the test results are more meaningful and dependable. -- Philip _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
