Glow plugs not so glowing

[Selkirk_D]

As @NIW asked what is the voltage with the ign. sw. in the crank position? The glow plug circuit goes through the glow plug in the preheat position so the voltage and current will be limited during preheat. During cranking the circuit goes directly to the glow plugs so you will get battery voltage minus any voltage drop in the circuit.

You can perform a voltage drop test by placing one lead of your voltmeter on the batt. terminal and the other on the glow plug terminal. This will tell you how much voltage drop there is across the switch. Remember there is a G1 and G2 terminal. One for preheat and one for cranking.

Got it!

Can’t run Wolfman’s test until I get dash hooked back up

 

[ruger1980]

Got it!

Can’t run Wolfman’s test until I get dash hooked back up

After rereading my post I wanted to make myself more clear. By testing I am saying testing of the ign. switch. So test from batt terminal on the switch to the glow plugs terminals on the switch. Also the circuit has to be complete and loaded when performing a voltage drop test

 

[Selkirk_D]

After rereading my post I wanted to make myself more clear. By testing I am saying testing of the ign. switch. So test from batt terminal on the switch to the glow plugs terminals on the switch. Also the circuit has to be complete and loaded when performing a voltage drop test

Thanks for clarifying. I’ve essentially done that test for the preheat position. .25 ohm resistance, 12.5v into switch. 11.5 at glow plug terminal of switch, no load, 9.25 out at glow plug terminal under hood. With indicator connected. I’ve had the battery on a battery tender for a day or so . Hopefully starting voltage will be higher.

So I just checked ohms though switch in crank position. It was flaky at best. Intermittent continuity, but looks like around .25 ohms as well.

Running Wolfmans test, I get 12.65 going into the switch ( after charging battery) and intermittently get 9.48 volts in the engine compartment with the glow plugs disconnected. I thought I had a bad connection on my alligator clips, but I checked and rechecked test leads several times. I repeated the ohm test in switch preheat position , consistently got .25 ohms.

Looks to me like glow contacts in the ignition switch are indeed toast.

 

[ruger1980]

Thanks for clarifying. I’ve essentially done that test for the preheat position. .25 ohm resistance, 12.5v into switch. 9.25 out at glow plug terminal under hood. I’ve had the battery on a battery tender for a day or so . Hopefully starting voltage will be higher.

So I just checked ohms though switch in crank position. It was flaky at best. Intermittent continuity, but looks like around .25 ohms as well.

Running Wolfmans test, I get 12.65 going into the switch ( after charging battery) and intermittently get 9.48 volts in the engine compartment with the glow plugs disconnected. I thought I had a bad connection on my alligator clips, but I checked and rechecked test leads several times. I repeated the ohm test in switch preheat position , consistently got .25 ohms.

Looks to me like glow contacts in the ignition switch are indeed toast.

Measure voltage drop using the method I describe not ohms with your multimeter. This is a much easier and accurate test.

 

[Selkirk_D]

Measure voltage drop using the method I describe not ohms with your multimeter. This is a much easier and accurate test.

As stated above, 12.65 in, 9.48 at the firewall, no plugs connected, just the glow indicator. Similar results to glow position test, other than contacts making intermittent contact. I’ve ordered a new switch and glow indicator. With indicator in circuit, voltage should supposedly drop 1.0-1.5 volts, assuming switch can pass the required current, which apparently it can’t. I’ll retest after new parts are installed and post the results.

 

[ruger1980]

OK don't listen

 

[hagrid]

@Selkirk_D doubles down with 19 showing!

 

[Selkirk_D]

OK don't listen

pretty obvious

@Selkirk_D doubles down with 19 showing!

I’ve ordered parts. No point in further testing at this point. Pretty obvious that many of you don’t bother to read the results I’ve posted thus far. I appreciate the help, but nobody seems to comprehend that the switch is bad.

 

[hagrid]

Not a blackjack aficionado then?

 

[Savoy John]

The manual for my B2710 says voltage to the glow plugs should not exceed 10 volts or risk burning up the plug.

 

[North Idaho Wolfman]

pretty obvious


I’ve ordered parts. No point in further testing at this point. Pretty obvious that many of you don’t bother to read the results I’ve posted thus far. I appreciate the help, but nobody seems to comprehend that the switch is bad.

I never seen you post what voltage you got at the glow plug feed wire when you just cranked it?

 

[Selkirk_D]

The manual for my B2710 says voltage to the glow plugs should not exceed 10 volts or risk burning up the plug.

Thank you for the info.

 

[Selkirk_D]

I never seen you post what voltage you got at the glow plug feed wire when you just cranked it?

I never seen you post what voltage you got at the glow plug feed wire when you just cranked it?

Sorry Wolfman, I posted it in post 43, 9.48 volts but battery had been on battery tender for a few hours so starting voltage is slightly higher than in preheat test. The main thing in the crank position is that the glow switch is making intermittent contact.

 

[Selkirk_D]

So finally got new switch and glow indicator installed. Connector at firewall shows 11.25 volts on preheat with no plugs connected. 11.02 volts cranking. Indicator glows nicely now. True test will be how easy it starts when temp drops below 20. Likely this fall. Thanks Wolfman, as usual you were right on.