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Old 07-03-2018, 03:54 PM
deek deek is offline
Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
Posts: 309

Disassemble a real Bendix keyswitch and a clone ACS keyswitch and you will see why the original Benidix version cost ~ double what the ACS Manufacturing version does.

I've seen the same problem as the OP on several XHB (including a Lancair of my own) with the ACS switch; never with the Bendix version.
'83 LongEZ - N888EZ 3,314 hours
'89 LimoEZ - N26EZ 686 hours (sold)
A couple of Glasairs and a Lancair 320...
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Old 07-03-2018, 03:57 PM
Dale D's Avatar
Dale D Dale D is offline
Join Date: Aug 2017
Location: Zeeland, MI
Posts: 21

Originally Posted by airguy View Post
Interesting how things work out...

I have the same ACS key switch in my plane, and for 260 hours it has worked flawlessly. This past weekend I experienced the same symptoms that were laid out here in this thread while starting up for an IFR training flight. If the key was rotated hard against the stop, the contactor dropped out. Back off just a hair and the contactor picks up and the starter engages.

I guess I'll replace the rotary key switch with two toggles and a pushbutton as others have recommended.
My starter has been flawless on the first attempt, since backing off the key rotation.
In case you want to try giving your ACS switch new life, Spruce sells an ACS service kit (Part #11-03654) for around $17 that replaces internal switch contacts and addresses an ACS service bulletin released back in 2008.
I'm expecting delivery of one of these kits any day.
I did confirm that my starter contactor "drops out" at full-clockwise rotation, so it is either an internal switch contact issue or a switch end-stop issue. I like the security of a key for the ignition and canopy.

I'm not convinced that toggles and push-buttons are immune to failures, too.
Dale DeWeese
RV-9A Owner
EAA Chapter 211 Member
Zeeland, MI (Z98)
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Old 07-03-2018, 04:26 PM
Sam Buchanan's Avatar
Sam Buchanan Sam Buchanan is offline
been here awhile
Join Date: Dec 2004
Location: North Alabama
Posts: 3,851

Originally Posted by Dale D View Post

I'm not convinced that toggles and push-buttons are immune to failures, too.
Anything can fail but the failure mode is a very simple one. The toggles and pushbutton on my RV-6 have been flawless since 1999 (hope I don't jinx them...) but a failed switch is easily diagnosed (jump the terminals) and can be replaced for less than $10 at the local auto parts emporium. I also have the "starter ON" light to bring to my attention a stuck solenoid.
Sam Buchanan
1999 RV-6
1918 Fokker D.VII replica

Last edited by Sam Buchanan : 07-03-2018 at 04:30 PM.
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Old 07-03-2018, 04:36 PM
Canadian_JOY Canadian_JOY is offline
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 1,858

In addition to the flaky "start" contacts, the ACS and Bendix switches have been prone to similar contact-related issues with the P-lead portion of the switch.

It used to be that I would trust an airplane when I could see the keys on the glare shield. Now, having seen some really ugly key switches (including the one where the key fell out onto the floor during climbout, with the engine still running - yikes!), I will only trust a key switch if I was the last guy to do a live mag check. Even then there's not so much trust as a slightly lower level of suspicion.

Key switches have been in service for many years in much of the GA fleet, with many of these switches not having been shown any love since they were installed on the factory floor several decades ago. Their function is something of which we should all be more than a little suspicious.

The nice thing with toggles for the ignition and a push-button for the starter is that troubleshooting is easy, replacements are cheap and one doesn't have to remove at least 5 wires to change a switch!
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