Hi folks, I'm new to airheads, but keen to learn. I recently picked up a 1976 R90S that I'm trying to get on the road and I made a rookie mistake. I failed to disconnect the battery before removing the front cover to inspect the points. Yup. So... I believe that something shorted out... the condenser? or diode board? now I have no spark and I'm looking for some advice on troubleshooting the short circuit. The starter cranks, engine turns over. I've got a multimeter in hand. I would appreciate any guidance or advice. Thanks, and peace & love
Was there a spark? Did the motor run BEFORE this incident? The most likely trouble arising from a front cover pulled on a hot electrical system would be a wrecked diode board. That would not prevent a motor from running by itself. Need more info to help. A wrecked dioode board will allow the batterry to run down while the bike will stiill rrun.
former Airmarshal, IL.
There are fuses to check first. These are the white German tubular type used in VWs that are about 1/2" long. They live on the multicolor circuit board in the rear of the headlamp shell. There are 2 of them and they are both 8A. Remove the HL reflector unit and you'll see them in there. Go ahead and buy some spares for the toolbox. Those fuses can be very hard to find out on the road.
Typically you will burn up the diode board when you fail to disconnect the battery. Always disconnect the Negative lead from the battery, and never from the gearbox end.
This is a 3-phase diode board so there are 6 diodes. If you know your way around a multi-meter you can test those diodes really fast and make a good call as whether or not to replace.
Originally a lot of the older diode boards were rubber mounted. The revised way is to solid mount these on metal standoffs for more reliable connection. That's a good upgrade to make if the diode board comes off.
Hope this helps !
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
It's a good idea to check your fuses, however, fuses on early airheads are associated with lighting circuits, not ignition. If your bike has points in the primary ignition circuit, look for 12 volts at the connectors on the condensor and then the points. If you have 12v at the points, youwill have to lift the fuel tank and check the wiring on the coils.
former Airmarshal, IL.
Check for 12 volts at the condensor with the ignition switched on. If you want to text me to set up a phone call, 309 251 0877.
former Airmarshal, IL.
Thank you Wobbly, I'll check the fuses- the headlight works, but sounds like I should keep a pair of 8A's in the repair kit.
Thank you 8053- I'll send you a text to set up a time to chat
peace,
hexdall
i believe the H/L in this year doesn't have a fuse so there should be light
as wobbly said check the diode board first.
check the blu/grn wire to the coils to read 12vdc after the switch is 'on'. again the fired ?˙†π§ something you think you have should not effect the voltage to the ign points or condenser.
grn or blu /grn are 'switched' power to
red is hot all the time
brown is ground
while your poking around visibly check the cleanness of ALL connections, even fuses male /female
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