[Vwdiesel] glow plug amps

paul lew biovolks at yahoo.com
Mon May 7 16:50:59 EDT 2007

I totally agree,I have one permanently mounted, that way I know if even one is even getting weak, and because I have it on the main line going into the car cabin (so I'm not measuring the starter), I can see if there is any drain anywhere else. and when the plugs are actually turning on/off, because some glow plug circuits will fail causing it to turn off too soon ,or stay on too long.


Message: 1
Date: Fri, 4 May 2007 15:11:28 -0700
From: "William A. Thompson" 
Subject: Re: [Vwdiesel] glow plug resistance
To: "Vwdiesel at vwfans.com" 
Content-Type: text/plain; charset="iso-8859-1"

Be careful about powering a glow plug on the
bench. They get red hot very,very fast and could
sorta' explode because there is no engine to sink
the heat to.

For various reasons resistance measurements, don't
seem to me, to be much of an indicator of a plugs
condition other than a basic "go .... no-go" test.
Even then interpretation of the actual resistance
can be misleading. Amp readings are near foolproof
... but for the possibility of sparks flying.
(VBG as I am guilty.)

I use a common 60 amp +/- ammeter just like one
you would buy to mount on the dash. Since I have a
few Rabbits I don't permanently mount the meter.
Make sure that you use big honkin' cables too
'cause you could be drawing in excess of 60 amps
at times.

I have used the meter on the bench but I prefer to
test them while installed in order to have the
engine for a heat sink. It helps to test the
plug(s) in the new condition so you have something
to compare to as time goes by. The total amps (and
the resistance to some degree) will change with
time even though the plugs are working fine. I
haven't tried this but it might be of benefit for
someone who lives in the extreme cold to keep a
running record of the diminishing amps (with a
better meter) to get an idea of when it might be
prudent to think about replacing them.

Put in new glows, put the meter in series with the
buss and the glow plugs (either side of the fuse)
in order to get a reading when they are all new.
Later if you think you have lost one glow the
total reading should be near 3/4 of the original
total reading, 2 glows 1/2, etc.

You do have to test each glow individually to
isolate which is bad. Disconnect the buss at the
glow plug and hook up the meter in series. Each
glow should read about 1/4 of the total amps.

... Bill

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