The Glow Plug in the far left pic is not a good one because it is getting hottest at the wrong place on Element. That no good plug may actually Ohm OK.
The other pic on the right is a good Glow Plug getting hottest at the tip of the element. The tip is the part that extends into the Precombustion Chamber.

Attached Thumbnails

   

__________________
84 300D, 82 Volvo 244Gl Diesel

This is the best piece of advice on GP's in the thread.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

I agree.

Do you think he lit his cigarette with the GP when he was done?

__________________

No, I did not light a Cigarette with it.
I smoked a Pipe back in the early 1970s for 2 years (Tobacco only) after which I lost interest in smoking.
But, like past President Clinton "I did not inhale".

__________________
84 300D, 82 Volvo 244Gl Diesel

I just bought 5 new Bosch. I have a pretty accurate Fluke. Just out of curiosity I measured the new and the old. 4 new were .8 and one was 1.2

The old ones were .4, .8, .6, .8, .2

So can we assume that the .2 one was the bad one or does resistance rise
as the fail, unless the element does burn out like a light bulb resulting in zero
resistance?

I just replaced ALL of mine beause I forgot about testing with a battery, although now I see that just glowing isn't all it needs to do, it needs to glow
in the proper way as well.

__________________
85 300TD FED-Daily
84 300SD-Wife's
86 XJS-Sunday
66 GMC-Work- Given to my stepson
83 BMW Airhead- Given to my stepson

The GP resistance is very high/open circuit when it fails. Not zero. GP in general measures at very low resistance, < 2 ohm, are good. I reckon all the old one your replaced are good. When GP glows, the resistance will kind of reaching a steady state and draws about 10 to 12A. Most GP are rated at 120-150W ( battery voltage x current drawn, 12v x 12A = 144W ).

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Tom, you can get a good meter at harbor freight for less than $20

We don't have one here. How about Autozoo?

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I appreciate the instruction, Diesel 911. Thanks!

__________________
'06 E320 CDI
'17 Corvette Stingray Vert

The glow plug on the right is either not powered up long enough or is not getting full current. I have never tested a glow plug with just the tip glowing. Unless all the glow plugs I have tested were no good?

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Pictures.

Never Touch Hot Diesel Glow Plugs!!!
http://www.peachparts.com/shopforum/diesel-discussion/134359-never-touch-hot-diesel-glow-plugs-post986836.html

NOTE:
I always keep one "NEW" glow plug in my tool box for demonstration/comparison testing.

Glow plug on the right been powered for 2 seconds. By 20 seconds the entire shaft (up to the bevel seal) should be glowing.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/28981d1129501651-never-touch-hot-diesel-glow-plugs-a1.jpg

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

It is a Monark not a Bosch glow Plug. And, it might be that I took the pic too soon. However, the point is that Heat strated at the tip and got hottest their first.

__________________
84 300D, 82 Volvo 244Gl Diesel