Testing glow plugs with charger
 

I have 4 old glow plugs from a 300D which may work perfectly. (one is broken) I've seen on youtube a way to test to see if they glow by attaching the positive lead from a battery charger to the threaded shaft, and the ground to the glow plug body.

I've done that will all my plugs, and none even get hot. Does this mean they don't work, or my battery charger is busted? The charger shows 12 Volts.

I have continuity in all the plugs, so is there a reason to replace them considering that they will probably cost me $30-40 each at a dealership?

THanks

Mark

I would check them with a well charged battery.

How many amps is your charger? Is it automatic?

-J

The current has to go somewhere.

Either you are not making good connection or your unit doesn't put out significant amperage.

Power (watts) = [E * E] / R

If it's 12 volts that's 144/R

Let's pretend there is 1 ohm of resistance. Then you are holding ~ 150 watt light bulb in your hand. You'd know if it was on!

With good current, a good glow plug will get red hot quickly.

-J

You don't really want to test 2 volt plugs with a 12 volt charger.

That could get expensive....

I wasn't sure if it was the series or parallel glow plug.

If you have a newer "smart" charger, it will not put out power unless it senses a connection to a battery.

I have an older charger that has no settings. I don't know why they don't glow. I even sanded the contact points. I tested the charger leads with my voltmeter and it read 12 Volts. :confused:

Are these the old loop style plugs? Did you check them with an ohm meter?

-J

I put the dial on ohms, and they read something like 6 or 7. They are the old style.

those are 6 volt plugs. DO NOT ground via body of GP, that wont work.

Apply ground to the threaded stud, and apply positive to the small ring around the threaded shaft which runs into the GP.

Helps if you use a thick buss wire and a ceramic insulator to test them...

I they read 6 or 7 ohms, they are good.

What was wrong with the broken one? Loop was open?

about 9 ohms is normal

More or less.

Depends on the temperature and the meter.