Glow plug weirdness - Page 2 - PeachParts Mercedes-Benz Forum

smitherz · #16 10-29-2011, 08:43 PM

Quote:

Originally Posted by funola

If you have an electronics background, you will know that most cheapo DVM's will not be able to measure resitance accurately in the 0.1 to 1.2 ohm range repeatably. I have come across glow plugs that measured 0.9 ohms yet would not glow when connected to a battery. It is better to measure the current drawn by a glow plug to check if they are good or not, which I am sure you know how to do.

As I was looking back over the posts I saw this one. You're probably right about measuring that low a resistance accurately. The only problem is that my meter only can handle 10A and most cheapy ones even less. If I recall my ohms law we would be looking at like 10-15+ amps depending on the condition of the battery and glow plug. It would make it much safer to fashion a sort of clamp-on ammeter to test these accurately.

Yak · #17 10-29-2011, 10:06 PM

Quote:

Originally Posted by tangofox007

In that case, a fine-tooth ratcheting combination wrench will make things much easier.

Any experience with the ratcheting open end wrenches?

Reviewed here: Craftsman 8 pc. Dual Ratcheting Wrench Set - Inch Reviews - Craftsman Community

vstech · #18 10-29-2011, 10:48 PM

while the open ends are helpful in many cases, they are not what I'd want turning the gp nuts... it's REALLY hard to fish them out from the IP crevasse....

Yak · #19 10-30-2011, 12:33 PM

Quote:

Originally Posted by vstech

while the open ends are helpful in many cases, they are not what I'd want turning the gp nuts... it's REALLY hard to fish them out from the IP crevasse....

I thought the crevasse was the old-GP disposal area. You just remove and drop them down there.

The extendible magnet-tool is a must-have.

barry123400 · #20 10-30-2011, 04:05 PM

Quote:

Originally Posted by smitherz

As I was looking back over the posts I saw this one. You're probably right about measuring that low a resistance accurately. The only problem is that my meter only can handle 10A and most cheapy ones even less. If I recall my ohms law we would be looking at like 10-15+ amps depending on the condition of the battery and glow plug. It would make it much safer to fashion a sort of clamp-on ammeter to test these accurately.

Make a shunt for your 10 amp max meter. It does not even have to be particularily acurate as you would be comparing plugs against each other for current draw. Usually takes about a foot of electrical wire and the instructions will be on the internet I think.

funola · #21 10-30-2011, 04:32 PM

Quote:

Originally Posted by barry123400

Make a shunt for your 10 amp max meter. It does not even have to be particularily acurate as you would be comparing plugs against each other for current draw. Usually takes about a foot of electrical wire and the instructions will be on the internet I think.

Good idea for those with only 10 A max DVM. Let me know what size and length shunt you end up using. My meter is 20 A max so a shunt is not needed. As I recall, a cold glow plug draws around 18 amps initially, as it heats up, the current slowly drops (as it's resistance slowly increase due to the heat) and settles to around 10 A when glowing full hot.

kerry · #22 10-30-2011, 04:58 PM

Step #1 in all glow plug work: Jam rags or paper towels down into the space between the block and IP to stop any stray nuts from disappearing.