[Vwdiesel] glow plug test

Roger Brown r.c.brown at ieee.org
Tue May 3 01:38:16 EDT 2005

Area31 Research Facility wrote:
> A normal battery charger won't have the 25 amps necessary to light a single
> glow plug, whereas the battery does.  The battery charger output would have
> dropped to almost zero volts when you put the glow plug on it's output.
> Rob
> ----- Original Message -----
> From: "mikitka" <mikitka at earthlink.net>
> To: <vwdiesel at vwfans.com>
> Sent: Monday, May 02, 2005 10:53 PM
> Subject: RE: [Vwdiesel] glow plug test
>>Well, I went back out and tried it again and no glow, sparks when I touch
>>clamps together but no glow on the plug, but when I touched the battery
>>terminals with that same plug and it sure did glow, bright red and fast
> too.
>>Could it be I have one of those automatic chargers that also senses if you
>>have the plugs hooked up backwards?

All depends on the charger.  My old 2/10A Century charger lights the plugs up no problem.  It does have a meter that reads up to 
12A, and it makes a bit more noise when you connect the glow plug.  I think the inrush current is in the 12-15A range, then it 
drops to around 8-9 according to my charger's meter.  Maybe you have a "smart" charger that senses the load and turns off the 
output if it sees something it doesn't like.  But if the battery works, then that is another way to test the plugs.

Actually I think the charger I have can put out around 20A of current, I was testing a starter solenoid once, had an ammeter in 
line and had clicked it on and off a few times, not really watching the meter.  When I looked down the meter was 19.something 
amps and the little test probes were very warm and the insulation was getting soft.  I figured the starter solenoid only pulled 
a few amps, not 20.


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