M916 ignition switch wiring

[Falcon]

Having trouble with ignition switch wiring. when the switch is turned on the starter starts cranking, starter start button does nothing. The wiring diagram shows a diode in the push button wiring but can't find it to test. Anyone know were it is located or what it looks like? A good picture of the back of the key switch plug may be helpful. Thanks

 

[simp5782]

I can get you one tomorrow.

I've never found the diode. If you remove the wires from the fuse box solenoid does the power drop leaving it?

Do you have the stock starter or do you have a gear reduction type on it Now?

 

[Falcon]

Original starter, The truck has always had a bad voltage drop when turning on head light, heater etc. voltage would drop down to 10v. Also it never kept all batteries in balance had to put on charger every few days. So I just did the alternator up grade to a 130 amp 24v and 24 to 12v 100 amp converter. Great battery charging but still had voltage drop when turning on accessories but had good voltage at converter output.
Ran a temporary wire from converter to ignition switch with having very little drop so assumed bad wire or connection causing voltage drop with load. Next ran new wire from converter to ignition switch thats when trouble started?? may have plugged new wire in wrong switch plug hole or something. If looking at the wiring schematic right I think I need to go from converter to #2 breaker first then to switch I may be bypassing the breaker protection or if there is a diode causing a backfeed. I must be missing something simple because the switch and push button starter was working before.???

 

[simp5782]

Original starter, The truck has always had a bad voltage drop when turning on head light, heater etc. voltage would drop down to 10v. Also it never kept all batteries in balance had to put on charger every few days. So I just did the alternator up grade to a 130 amp 24v and 24 to 12v 100 amp converter. Great battery charging but still had voltage drop when turning on accessories but had good voltage at converter output.
Ran a temporary wire from converter to ignition switch with having very little drop so assumed bad wire or connection causing voltage drop with load. Next ran new wire from converter to ignition switch thats when trouble started?? may have plugged new wire in wrong switch plug hole or something. If looking at the wiring schematic right I think I need to go from converter to #2 breaker first then to switch I may be bypassing the breaker protection or if there is a diode causing a backfeed. I must be missing something simple because the switch and push button starter was working before.???

Headlight draw is cause there is no relay to handle the power load. There is an upgrade thread on this. Generally it just burns the switch out and trips the breaker.

You need the converter to be switch on by the Main power switch or by a disconnect switch so it doesn't backfeed when it is shut down and draw power to the 12 or 24v side. I hooked the 12v you had in the battery box directly to the equalizer.

 

[Falcon]

Ok, I did just pick up a battery disconnect switch for that reason because it sometimes don't get started for several days . Also don't have to worry about something shorting out.

 

[Falcon]

Hey everyone finally found the problem. I replaced the starter solenoid in the dash the same time I did the alternator upgrade. Turns out the solenoid coil was grounded through the base causing the starter to engage when you turned the switch on. Its supposed to ground through the starter push button. Two post solenoids coil should not be gronded to the base, must have got a bad one.
Anyway on to the next issue, adding a hydraulic valve for a detach and dump trailers.

 

[simp5782]

Hey everyone finally found the problem. I replaced the starter solenoid in the dash the same time I did the alternator upgrade. Turns out the solenoid coil was grounded through the base causing the starter to engage when you turned the switch on. Its supposed to ground through the starter push button. Two post solenoids coil should not be gronded to the base, must have got a bad one.
Anyway on to the next issue, adding a hydraulic valve for a detach and dump trailers.

Your winch control doesn't have the aux port?

 

[Falcon]

Yes it does to supply a remote valve, I found a couple post on here.

 

[Castle Bravo]

Glad you got it fixed.

When I first read the symptoms, the unusal way the coolant temperature light diode is set up came to mind. Here is an email I sent to someone a few years ago about that -

"You'll have to excuse the strangeness of the diagram, I removed all the unrelated parts to clarify the engine temperature idiot lamp.

The lamp is in the lower right corner and is fed by wire 44 from circuit breaker CB-6. It finds a path to ground through wire 55A, 55, and 55B on the other side of the firewall bulkhead connector. This then goes through the engine temperature switch to ground. The switch is normally open and closes above 225°F to illuminate the light.

The "Copper stud" is the battery side of the diode D1. Wire 55A connects to the anode and 55C to the cathode. (They think of everything...) The engine temp lamp illuminates when you press the engine start button as it finds a path to ground through the switch. (46A or 46F) The diode is there to ensure that if the engine lamp should illuminate while the truck is running, it doesn't also engage the starter via the start button.

A few days ago, I grounded wire 55B to the engine to see if the lamp would illuminate while the truck was running and I think I heard the starter engage!

I am going to test the diode today and see if it is working correctly. If it isn't, I may just ditch that setup figure out another way to provide a test function for the light. I mentioned that I removed a 250°F switch from the truck and have since replaced it with the correct 225°F switch. I don't think my truck has ever gotten that hot while I've had it, so I don't think I've inadvertently engaged the starter."