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Mar 27, 2025 | 12:40 PM

#16

BigBlue2

Lead Driver

Joined: Apr 2002

Posts: 5,363

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My leads were 0.1 ohms, the new plug was 1.1 ohms, so 1 ohm seems good. I touched the connection and the top of the threads.

Mar 27, 2025 | 05:53 PM

#17

BigBlue2

Lead Driver

Joined: Apr 2002

Posts: 5,363

Likes: 1,258

Quote:

Originally Posted by ihc1470

Ohms law for amps is voltage divided by resistance. So lets say you have 10 volts to the glow plug system and you divide that by your 1.0 ohms resistance that gives you ten amps of current draw. A good plug draws around 20-22 amps. All 8 plugs will draw close to 200 amps if the system is working right. So I would say you have bad plugs. Go to an auto parts store and buy a 30-0-30 amp meter and test then using that. Look for that 20 amp draw.

The resistance of the entire circuit, including wires, relays, glow plugs and ground path to the battery would be needed to back out a calculation of the entire 200 amp draw. The glow plug is just a portion of the resistance.

Mar 27, 2025 | 06:36 PM

#18

ihc1470

Tuned

Joined: Jun 2013

Posts: 441

Likes: 61

From: Craigmont, Id

Quote:

Originally Posted by BigBlue2

If you measure off the output stud of what ever sort of relay your system is using the only part of the circuit you will find resistance is the left and right bank glow plug harness which will have the eight connectors, the glow plugs themselves, and what ever resistance is in the ground circuit.

If you use an inductive amp meter you can test the system in less than a minute to determind if you have eight working glow plugs, having done so without moving one connection. You can narrow it down to left or right bank issues by clamping around the harness feeding the bank in which case you will see around 100 amp draw if the plugs are all good.

As was pointed out by a couple of other posters resistance of test leads certainly enter the picture when you are measuring such low resistance. A test light or ohm meter are going to show you that you have a circuit, however a half ohm difference is quite a difference in this application. Just saying that a test light or ohm meter while a good way to test may not be the best way.