ELECTRIC UNDERCARRIAGE. partial retraction when engine running

[Rod Witter]

I have a problem of the u/c only retracting about 2/3rds when the engine is running.

I understand this is caused by RF interference from the ignition - since the up limit is not a microswitch (as is the down limit which gives green light) but a counter for the number of revolutions of the screw jack.  (Which gets muddled by RF)

The factory provided a revised control cable for the u/c but this did not solve the problem.

I tried fitting 5Kohm plugs AND 5kohm plug caps and the problem went away  (also much less interference on the radio) - but this is not recommended by all authorities, and I was finding that the black dust build up in the plug caps was bad.

I have returned to NON resistive plugs and  5Kohm plug caps, but the u/c problem has returned.

I will live with it for the moment. (retract after engine off) But I think that I may go back to resistive PLUGS AND CAPS  ( i.e. 10Kohm total) and ensure a better connection of the cap by the sideways pull of tie wraps (as reported by other contributors).

The RPM was always fine and mag. drop OK , so I am not sure why the combination of resistance in PLUG and Cap is frowned on ?

Any body throw any light on this ?  I would be amazed if mine (Serial 227) is the only one with the problem !

[bucc...@gmail.com]

[Chester Fitchett]

Pretty difficult to properly shield a cable against that sort of interference.  I had an APIS with the same issue, the noise showed up on the tach input.  Used several Wurth ferrites on the cable harness that included the tach input.  Can provide part numbers if desired.