How does a glow plug work?

   / How does a glow plug work? #1  
R

rasorbackq

Platinum Member
Joined
Aug 31, 2011
Messages
573
Location
Springfield Nova Scotia Canada
Tractor
Branson 4720
So at the beginning of the season noticed tractor (brandson 4720H) was getting harder to start on cool mornings. To a point when it just didn't. Just rolled over and over. We had a break in the temp a little so I picked up 4 glow plugs Thinking I could replace them all or what ever was required. . Since I had to remove the metal strip running to each plug and just replaced the first 3 . Last one is very difficult to get to.. 30 minutes later I'm all done . Fires right up in 5 seconds. Next day 5 seconds . Next day 5 seconds. Today no go. Glow plug light on dash is not even lit. Checked all fuses all good. So what is the power that a glow plug operates on . 12V?? Is there any other devices or moduals if the lineto operate a glow plug?
All I can say is the glow plug wire is about 3 " long before it enters the harness. This is as far as I got so far. Storm coming in 4 days. Needs to be running.
 
   / How does a glow plug work? #2  
A glow plug works pretty much like any heater - apply voltage and it gets hot. Glow plugs normally get 10.5 volts though there are exceptions. Put a meter on your glow plug to check what voltage you're getting. Some glow plug circuits depend on a series resistor to drop the voltage. Some have an electronic controller and relay. You probably need the schematic for your specific tractor to see what's going on. If you want to measure current to see if the plugs are working figure on ten amps per plug.
 
   / How does a glow plug work? #5  
As DL implied you definitely have some sort of controller or relay in the glow plug circuit. It may run on the five amp fuse but the glow plugs, when intact and energized, will draw about forty amps. You really need a circuit diagram to determine exactly how the glow plugs work. The controller will probably have internal regulation to limit your glow plugs to about 10.5 volts. It will NOT be direct wired from a switch.
 
   / How does a glow plug work?
  • Thread Starter
#6  
So without a drawing should I be looking inside console under the dash or under the hood . Maybe cut open the harness and start following?
 
   / How does a glow plug work?
  • Thread Starter
#7  
So without a drawing should I be looking inside console under the dash or under the hood . Maybe cut open the harness and start following?
 
   / How does a glow plug work? #8  
I would try to find a manual first, then look under hood or "dash" for what may be a grouping of relays..... Cutting open a harness should be a last resort or just plain desperation... Did you check manual for tractor , mine has rudimentary wiring diagram included.... .
 
   / How does a glow plug work? #9  
The 5 amp fuse is going to be going from the switch to a relay or glow plug controller.
Starting under the hood try to trace back the heavy wiring from the glow plugs to were it goes.
In the Branson section of this forum all the service manuals have been linked for down loading
they will help you find what you need
.How does a glow plug work?
 
   / How does a glow plug work?
  • Thread Starter
#10  
So without a drawing should I be looking inside console under the dash or under the hood . Maybe cut open the harness and start following?
 
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