Our Bosch DU stopped working. It sputtered a short time, then quit. I've checked voltage to the distributor (rod going into distributor) and it reads around 9,000 volts. Took off the porcelain cover so the "safety" could be bypassed and still no voltage to the plugs from the distributor.
I'm not sure how I can show this much voltage at the rod and still nothing at the distributor?
Could this be a condenser problem? Any troubleshooting suggestions?
Only 9000 volts is pretty weak........a good mag should put out enough juice to jump a 3/8" air gap.
Is it intermittent?
If you get a couple good sparks before it pukes it's most likely the condenser.......hopefully.......because if it's the coil you're in for an expensive repair.
If you're creative you can wire in an "orange drop" modern capacitor but requires yanking the entire armature, un-soldering the capacitor (at the front end of the armature), removing the guts and replacing it.
To rule out a crap connection between the armature commutator and distributor remove the output tower and the rear of the mag and check for a stuck brush........it happens.
Take a piece of wire, ground one end to the mag, hold the other end 5/16"-3/8" from the slip ring and see if you get spark there.
POINTS can be REAL fussy.......and there is no exact setting........you need to play with them until you get the best spark.
I hope this helps.
Bosch's are my favorite of favorites but when the coil pukes it's expensive.
I would start by checking spark plug gap. At 9000 volts you probably have weak magnets. Decreasing the plug gap to .020" might get you down the road for a few more drives. You have to tear down the magneto to recharge the magnets, not something that can be done by just anyone.
These high tension mags are not noted for their reliability. A spare one in the trailer is a good idea if you want to be sure you are going to be able to finish every tour.
The Dykes manual gives a very detailed description of how to troubleshoot your Bosch magneto. Here are a few pages that should help:
Thanks, found the culprit. The brush pickup terminal had a deep carbon track/burn. Evidently it shorted out while running, causing the quick loss of spark. I took a spare untested mag and replaced the part, now showing 50-60,000 volts at a fast idle. Old Car Festival, here we come.
Carbon burn from the brush to the brass threads:
Voltage after replacing:
Glad you bought that spare mag from me, Rob.
Always good to have spare parts......
That car just seems to give you all kinds of trouble. Maybe you better just drop it off by John Regan's house on your way to the OCF and enjoy your N. I will come and get it from John so it doesn't clutter up his driveway. Those pre-N cars just don't seem to work that well.
I's that darn after market Simms-Bosch magneto.....
Ford originally used their own magneto, and we're in the process of restoring the system. Meanwhile we're stuck with the unreliable Bosch high tension mag. Wait a minute, Pierce, Thomas and even the RR Silver Ghost all used the Simms-Bosch mag.
Fortunately, the Model K was the only production Ford to have two separate ignition systems, so I was ale to get home on the coils and timer.
Have a good weekend,
Had one go bad without warning, had to have it rewound(not cheap). good thing we had a spare Mag on the shelf.