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Starting current draw changed?

567 Views 2 Replies 2 Participants Last post by  tcnofh1
I normally turn on the glow plugs, wait until they are finished heating, then engage the starter.
Glow plugs draw lots of amps, so I watch the volt meter I installed to see when the GP relay opens.
Voltage normally sags to about 11, then bounces back to 12+ after the GP relay opens.
Now the voltage drops to 9 when I turn on the GP.
Glow plugs normally fail electrically open, is that right?
So if there was one or more GP dead, I would expect less current to be used, and less voltage sag, not more.
Hope the problem is that the 3 year old batteries are shot, as changing glow plugs with the body on the van chassis is probably impossible.
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Could be a high resistance somewhere in the circuit to the GP relay. Just a corroded battery post could do it. Start there, and maybe get the batteries load tested.
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I cleaned the under-hood battery terminals, GP load voltage drop is back to abby-normal!
WIll clean the frame mounted battery terminals in a few weeks, too hot & humid here now for that job,
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