i tested some glowplugs today.

[chris142]

When i got my truck i saw that it had new glowplugs in it i didnt know what brand and you guys got me scared so i bought 8 new beru ones and put those in. It had delphi ones. Today i found them so i hooked 1 up to a 12v battery. It got red then burned out after about a minute.

It did not swell up though. I redid the test on a 2 nd one and it did the same...how long should they work before they burn out.

 

[Mulochico]

Figure they only glow for about 8-10 seconds with the controller.

 

[GOOSE]

I would venture to say that they all will blow if you let them eat for a minute or more at a time. There isn't any cold metal to draw the heat away from them either. I'd say your test may provide good insight as to how they heat up but that's about it. I'd save the rest of the good ones for spares, even the Beru's give out after a few years.....

 

[chris142]

I was mainly wondering if they would swell up before they burned out. Assuming that this was an adequate test they did not swell up. Maybe the delphi ones are safe?

 

[HammerDown]

I was mainly wondering if they would swell up before they burned out. Assuming that this was an adequate test they did not swell up. Maybe the delphi ones are safe?

Not every glow plug that burns-up, swells-up.
Usually on a frigid day, a 12 second burn is about the max I've seen.

Autolites seem to have the worst reputation for 'swelling'
Some say Champions are bad too, but can't prove that by me as I've used them for many-many years without issues.
Just the other day I installed 8 Motorcraft ZD-9 (beru) only reason I purchased them was I had a $20 credit from AutoZone plus I got another 15% off as my neighbor works there.
Like diesel fuel...GP's are just stupidly over priced.

 

[racer30]

The glow plugs are designed to have 6 volts during operation. That's why there is a z shaped metal resister on the 7.3 to regulate the voltage the plugs see. Testing them one at a time with 12 volts won't give you much good info.. other than how long they will burn with to much voltage. I ran two champion glow plugs along with 6 beru's and both champion's failed and swelled just enough to be a pain to get out. only lasted a few weeks. Now all are zd-9's...They work the best when all matched plugs so all the resistance is the same plug to plug...

 

[franklin2]

The glow plugs are designed to have 6 volts during operation. That's why there is a z shaped metal resister on the 7.3 to regulate the voltage the plugs see. Testing them one at a time with 12 volts won't give you much good info.. other than how long they will burn with to much voltage. I ran two champion glow plugs along with 6 beru's and both champion's failed and swelled just enough to be a pain to get out. only lasted a few weeks. Now all are zd-9's...They work the best when all matched plugs so all the resistance is the same plug to plug...

They are 6 volt, but the z shaped resistor is not there to regulate the voltage the plugs see, it's there to give a signal to the glowplug controller brain so it knows when to cycle the plugs off. In other words the glow time/versus ambient temperature. There will be a very slight voltage drop across this resistor, and that's what the brain monitors to decide how long to cycle the plugs.

 

[racer30]

I see your point.... I Know the plugs resistance changes depending on temp.. I didn't think about how it was measured by the controller for cycle time... I also believe the wire size to the plugs is also used in the total resistance calculation... I have seen people run there own heaver wire and have plug longevity problems if they change to a larger size wire capable of more currant with less resistance. So, The plugs resistance combined in the parallel circuit create the load necessary to bring down the voltage through the wire's resistance and the z resister where its measured by the controller.... makes sense to me.... Learn something new every day.