Test Glow Plugs

[BigRedWeather]

My reading says a Glow Plug (GP) should show between .2 and .6 Ohms of resistance if it is good. I just tested 4 GPS and they all read .001 Ohms.

Then I pulled out a GP that came off my truck and put 12 volts to it and in 2 seconds it was red hot and kept getting hotter. That seems to be a good GP to me. But when I checked its resistance it was .001. So either .2 and .6 Ohms are the wrong specs or the GP that glowed for me is actually bad.

Can someone straighten me out on this? I would love to see some authoritative Ford specs on this.


BigRedWeather

 

[leojr]

Where you checking the resistance of the glow plug removed from the head? I suspect that the glow plug being encased in the metal of the head changes the resistance. But I'm really just stalling and keeping this thread towards the top until someone that knows the answer comes along...

 

[RenoF250]

What were you using for a meter? Resistances that low are difficult to measure, I suspect your meter is not that good and the batteries are possibly a bit low. I have some cheap meters for beaters when I just need a number that is close but if you want to measure anything you need a Fluke meter.

 

[BigRedWeather]

My meter is a $20 Sperry (?) meter. But resistance is resistance.

Any comments on whether the GP I tested out of the engine, above, is actually good?


BigRedWeather

 

[argve]

it's good. Slap it back in and enjoy.

On a side note.... The better the meter the better the reading you will get. As stated Fluke is the industry standard.

Now as far as Glow plugs go - a resistance that lower than say 20 ohms is good. I have never seen a bad glow plug read anything lower than Kilo ohms. Basically they are little heaters so anything that is close to zero is GOOD. as I said before it's good and slap it back in and enjoy.

 

[Double-S-Diesel]

Ivbe had anywhere from .003 to .007, some times depends on the metere or the connection, bascially as long as its not high , or not 0 its good

 

[Bashby]

What range did you have your meter set on? .001 reading on the Kohm scale would be 1 ohm.