[Vwdiesel] glow plugs

[Roger Brown]

Pam & Doug Boes wrote:
> 
> Is it common for all four glow plugs to fail at about the same time? 

They can, after all, they have all seen the same number of cycles and environment.  So, if they were all of equal quality they
may have a similar lifetime.  Could also be you had one or two that were already burned out and did not know it.

> If
> one or more glow plugs are shot, do the remaining plugs each get more
> current because they are connected in a paralel circuit? If this is the
> case, does the failure of one quickly cause the failure of the rest from
> over current (overheating)?

No, the current in each parallel branch remains essentially the same.  Might be a few percent higher with fewer plugs since
there is less voltage drop in the circuit.

> Can cycling the glow plugs on especially cold days cause them to fry
> faster?.

Yes, the do have a maximum on-time, unless you have the newer style ones.


> Normally, I go to the block heater when the overnight temperature goes
> below 10 F. Last night, my daughter forgot to plug hers in and the temp
> went to 4 F this morning. No Start! I got it running this afternoon but
> later on it would not start again when the temp had improved to around
> 20F. I jumped it and had plenty of cranking but not even a wimper of
> firing. When I finally got it home around 8 this evening, I checked the
> fuse (only a 10 A on an 85 Golf?) and it was fine. I pulled the glow
> plug from #4 because it is the only easy one to get out and found it
> failed the ohm meter test for continuity. I'm sure the other three are
> the same way. I just had all of these  glow plugs out at the end of the
> Summer and they were all good.
> What would cause all the plugs to fail so quickly?

I like to test mine with a battery charger, very evident if the plug is working:
	http://www.4crawler.com/Diesel/CheapTricks/GlowPlugs.shtml#GlowPlugTesting


--
   Roger

Note: The shop will be closed for the holidays.