Glow plug question
Senior User
Joined: Nov 2009
Posts: 283
Likes: 0
I am no techie, but when did it become ok to limit amperage by wire size to cause such a situation on purpose???
I thought when you know you will have certain loads at various times of the year that you had better not underwire something with a potential draw that could heat/melt wiring and blow fuses, etc.?
I remember people screaming at me when I started rewiring our old travel trailer rebuild, about the wire sizes and lengths for our converter/charger and inverter. So I wired that stuff on seperate 5 foot runs directly to the batteries with 0 wire, and fused them like the instructions said at the battery
I thought when you know you will have certain loads at various times of the year that you had better not underwire something with a potential draw that could heat/melt wiring and blow fuses, etc.?
I remember people screaming at me when I started rewiring our old travel trailer rebuild, about the wire sizes and lengths for our converter/charger and inverter. So I wired that stuff on seperate 5 foot runs directly to the batteries with 0 wire, and fused them like the instructions said at the battery
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
They are not limiting amperage.
They are limiting voltage.
When you work in the electrical business, you have to take voltage drop into consideration on all of your calculations for wire size.
The more amps you try to get through a wire, the more voltage drop you have over the length of the wire.
Also the longer the wire is, the more voltage drop you have.
All they did was work the formula backwards to take advantage of what is a pain to most electricians.
That said, since the glowplugs are only on for 10 or 15 seconds, that overload becomes acceptable.
If you tried to run them constantly, if the glow plugs did not fail, the wire would.
As an example 200 amps on your house requires 3/0 copper cable, the same size as the battery lead down to the starter.
On your truck, the cable is only 4 feet long, but the 300 amp starter is going across a 3/0 copper cable.
Again a short term load.
When you were wiring your travel trailer inverter/charger, you were going to have things on for minutes or hours, not seconds.
Master electrician and electrical contractor here when I want to be.
I just have more fun running heavy equipment most of the time.
They are limiting voltage.
When you work in the electrical business, you have to take voltage drop into consideration on all of your calculations for wire size.
The more amps you try to get through a wire, the more voltage drop you have over the length of the wire.
Also the longer the wire is, the more voltage drop you have.
All they did was work the formula backwards to take advantage of what is a pain to most electricians.
That said, since the glowplugs are only on for 10 or 15 seconds, that overload becomes acceptable.
If you tried to run them constantly, if the glow plugs did not fail, the wire would.
As an example 200 amps on your house requires 3/0 copper cable, the same size as the battery lead down to the starter.
On your truck, the cable is only 4 feet long, but the 300 amp starter is going across a 3/0 copper cable.
Again a short term load.
When you were wiring your travel trailer inverter/charger, you were going to have things on for minutes or hours, not seconds.
Master electrician and electrical contractor here when I want to be.
I just have more fun running heavy equipment most of the time.
Senior User
Joined: Oct 2009
Posts: 193
Likes: 0
i put 8 new autolite glow plugs in my 93f350 to avoid winter problems. 3 weeks later
3 were already burned out. i had a problem getting one out because it swelled up
in the hole and was stuck. i used pb blaster and 3 hours of patience. i switched all
to motor craft and repaired 2 injection lines leaking fuel sometimes,which means
could pull in air and lose prime. now it starts in about 2 seconds at 34degrees
good luck p.s i learned the hard way
3 were already burned out. i had a problem getting one out because it swelled up
in the hole and was stuck. i used pb blaster and 3 hours of patience. i switched all
to motor craft and repaired 2 injection lines leaking fuel sometimes,which means
could pull in air and lose prime. now it starts in about 2 seconds at 34degrees
good luck p.s i learned the hard way
Elder User
Joined: Mar 2008
Posts: 912
Likes: 0
From: Marianna, Florida USA
fixitman1310, what was the type # of the Autolites you put in? I'll bet they were 1108s. 1109s are the temperature limiting ones. Also, it's wise to heat them on the bench befire you install them in case there is a problem. Better to find it before installing them.
Elder User
Joined: Jan 2008
Posts: 825
Likes: 2
From: SW Washington coast
And if it's fun, it ain't work ...
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
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