ok so doing a little math here:

Looking at the Diesel Giant page:
http://dieselgiant.com/glowplugrepair.htm

We see that glow plugs should read something under 1 Ohm. Let's say they should be .5 Ohm.

We got 5 of these plugs in parallel. The math for parallel resistors brings us down to .1 Ohm now. V = IR so we got 120A draw from the 5 plugs.

120A for 3 minutes? Really?

Ok so I got a 65A alternator. Let's be generous and say it is generating 60A most of the time (which is totally unlikely. 60A when idling?)

So it would take a minimum of 6 minutes of running the car to charge the battery back up from the drain on the plugs.

And that's assuming 1) 100% efficiency of charge/discharge 2) ignores starter motor drain 3) no other electrical appliances used

Given all the generous assumptions, it seems like it would take a minimum of 10 minutes to charge the battery back up every time you start it.

Strange.

Don't forget the the glow plugs (or any circuit for that matter) will draw more amps as they get hotter. The hotter they get, the more amps they will draw. Heat builds resistance in the circuit. Go junkin, swap the relay, move on to the next issue. Don't worry, there will be one eventually!

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'70 F100 shortbed
'82 Diesel Westy
'83 Euro 300TD
Curtlo Viper
Yeti ARC
Surly long haul trucker

That is an interesting theory. Perhaps you could explain in greater detail how increased resistance translates to an increase in current, assuming that voltage is constant.

The opposite is true of course. Another great example of dyslexia at work. I was unaware of my condition until now. Perhaps more sleep would help?

__________________
'70 F100 shortbed
'82 Diesel Westy
'83 Euro 300TD
Curtlo Viper
Yeti ARC
Surly long haul trucker

There is a thread from several years ago where I said also said that they drew more amps when they were hot.
And, of course people told me that is not so.
That may have been why I did the test with the Amp Meter.

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84 300D, 82 Volvo 244Gl Diesel

The above is not ture when it comes to the Glow Plugs.

I connected one Glow Plug in series with an automotive Amp Meter.

When I connected it to the Battery the Needle on the Gauge went to 60 amps (this is as high as that Gauge would read). It stayed at 60 amps for about 2 seconds and I observed that as the Glow Plug Element got hot the the Amperage it was drawing started to drop.

The Glow Pulg heated up the Amperage dropped down from 60 amps to 16 amps and stayed there.

So the as the Glow Plug heated up it drew less amps.

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84 300D, 82 Volvo 244Gl Diesel