Glow Plug Voltage

[Death Row Dave]

Does anyone know the correct voltage that should be at the glow plug , buss bar when they are heating . My battery is at 12.6 , voltage at glow plug buss is at 10.4 . Is this correct voltage for the glow plug buss when heating ? I can’t determine in my mind why there is such a small gauge (16 or 18) wire feeding current to the glow plugs , when exiting the relay is the power wire is a 12 gauge wire . Thank you and be safe

 

[Death Row Dave]

Does anyone know the correct voltage that should be at the glow plug , buss bar when they are heating . My battery is at 12.6 , voltage at glow plug buss is at 10.4 . Is this correct voltage for the glow plug buss when heating ? I can’t determine in my mind why there is such a small gauge (16 or 18) wire feeding current to the glow plugs , when exiting the relay is the power wire is a 12 gauge wire . Thank you and be safe

This is a 2810 series tractor

 

[RjCorazza]

@Death Row Dave
Not a mechanic, but that drop doesn't seem excessive considering the load that glow plugs put on a battery. If the glow plugs are doing their job for you, I would load test the battery itself to confirm it's condition, and call it good.

 

[Death Row Dave]

Battery load test , drops to 11.9 volts . The glow plugs simply can not put that much load through a 16-18 gauge wire , it’s over a 2 bolt drop in volts . The small wire would go up in smoke at the amount of load . I’m going to have to research deeper , follow through the wiring diagram . This is really strange . If the glow plugs are designed to use 12 volts it is a simple task to wire in a new relay and direct wire to the glow plugs full 12 volts when the relay is activated .

 

[RjCorazza]

Battery load test , drops to 11.9 volts . The glow plugs simply can not put that much load through a 16-18 gauge wire , it’s over a 2 bolt drop in volts . The small wire would go up in smoke at the amount of load . I’m going to have to research deeper , follow through the wiring diagram . This is really strange . If the glow plugs are designed to use 12 volts it is a simple task to wire in a new relay and direct wire to the glow plugs full 12 volts when the relay is activated .

Well, you're assuming that the actual glow plugs are the only, and final current draw. Aren't there resisters in glow systems that reduce current prior to the plugs, possibly before the small gauge wire?
I have no idea, but be sure to post your conclusions !

 

[LouNY]

If a glow plug is working you will not measure battery voltage when they are energized.
Even if measureing voltage at the battery + and - you should see a voltage drop when they are energized.

 

[Fuddyduddy1952]

Does anyone know the correct voltage that should be at the glow plug , buss bar when they are heating . My battery is at 12.6 , voltage at glow plug buss is at 10.4 . Is this correct voltage for the glow plug buss when heating ? I can’t determine in my mind why there is such a small gauge (16 or 18) wire feeding current to the glow plugs , when exiting the relay is the power wire is a 12 gauge wire . Thank you and be safe

Could the smaller gauge be for the relay coil and larger 12ga wire power to glow plugs?
I'd want a wiring diagram to see where voltage drop is. If you have, say, 12.6v on one side of relay contacts, 10.4v other side then relay needs to be replaced.
Does tractor start ok regardless of 2 volt drop?

 

[Chewwy]

Well, you're assuming that the actual glow plugs are the only, and final current draw. Aren't there resisters in glow systems that reduce current prior to the plugs, possibly before the small gauge wire?
I have no idea, but be sure to post your conclusions !

Resistors in series with glow plugs to reduce the current makes little sense.

 

[RjCorazza]

Resistors in series with glow plugs to reduce the current makes little sense.

Maybe I'm thinking that the glow plugs are the resistors, measured in ohms for testing?

 

[Anakist]

Yeah that's more correct. The glow plug is a resistor same as an old school light bulb.

James

 

[Death Row Dave]

Small gauge wire is at glow plug buss bar . The purpose of the relay is to keep high current loads off switch as do supply full battery voltage to the load circuit . I have throughly reviewed the wiring diagram there is no resistor in the circuit . I’m thinking the reducing wire gauge is limiting current flow measured in voltage at the glow plugs . My othe tractor is a MF , it has full battery voltage at the glow plug buss . I’m thinking of temporally wiring a 12 gauge wire from relay to glow plug and check operation .

The Mahindra will not start cold , new glow plugs already installed .

I’ll keep you posted on results of my test . Thank you for thoughts and responses

 

[doneill127]

My tractor has a MHI motor, believe yours is TYM. But the specs for the glow plug are 10.5v at 9.7amps. There are 3 plugs wired to a common buss. No resistors between the relay and buss. The buss connector has fusible link. Glow plugs should measure 0.55 ohms.
Don’t know if this helps

 

[Death Row Dave]

That helps a ton ! Thank you . Where were you able to locate this info ? Thank you so much

 

[doneill127]

My machine has a Mitsubishi S3L engine. Found MHI service manual and operation and maintenance manual online. Extremely detailed and very handy.

 

[hornett22]

Make sure you're getting a good connection at the connector to buss bar. The can get corroded.