Master solenoid - wiring

P

Phil007

Filing Flight Plan
Joined
Dec 1, 2018
Messages
11
Display Name
Display name:
Tractor1971
My Comanche 260 starter is cranking so slow that it fails to start. I found a voltage drop at my master solenoid from 12.5 V to 9.6 V. I took pictures of the wire connections,, and I’m wondering whether it is wired correctly. I need to find a used/other new solenoid, but want to be absolutely certain about my wire connections.
My common sense says that the diode is supposed to be connecting to the third post from the left. Any comments?
 

Attachments

  • 85498A08-4439-42F4-B690-8E50A844378C.jpeg
    85498A08-4439-42F4-B690-8E50A844378C.jpeg
    248.8 KB · Views: 35
Phil007 said:
My Comanche 260 starter is cranking so slow that it fails to start. I found a voltage drop at my master solenoid from 12.5 V to 9.6 V. I took pictures of the wire connections,, and I’m wondering whether it is wired correctly. I need to find a used/other new solenoid, but want to be absolutely certain about my wire connections.
My common sense says that the diode is supposed to be connecting to the third post from the left. Any comments?
Click to expand...
The way you have it drawn is right.

Are you getting that 9.6 volts during cranking?

You need to measure the voltage across the big terminals on both the master and starter contacts, during cranking. When the master is on, the voltage should drop to zero and stay there during cranking. Across the starter contactor, you should see 12 volts with the master on and not cranking, and that should drop to zero when cranking. Anything more than maybe half a volt or so indicates resistance in the contacts. Old contactor contacts oxidize, and the starter contacts burn as well.
 
Be careful with diode polarity..
 
Thanks for the feedback, the diagram confirms my wiring.
My voltage drop is with no load, just the master on. I actually opened up the contactor seeing that i just ordered a used one. I found a half a teaspoon of dust, and everything is covered in rust. I guess that would do it.
 
Phil007 said:
Thanks for the feedback, the diagram confirms my wiring.
My voltage drop is with no load, just the master on. I actually opened up the contactor seeing that i just ordered a used one. I found a half a teaspoon of dust, and everything is covered in rust. I guess that would do it.
Click to expand...
Ordered a used one? Might get a small improvement, maybe a better improvement, but used stuff like this will often have all the same problems the old one did. And measuring the resistance across the used solenoid won't tell you anything. It takes only the tiniest resistance to cause a large voltage drop with large current flows. Ohm's Law.
 
I had some issues like this with a 250 Comanche and approached it a little

different. Creative use of long heavy duty Jumper Cables resulted in a temporary

ground circuit and an ADDITIONAL path around contactors.

Two people and be careful.
 
You must log in or register to reply here.
Back
Top