Austin Healey 100/4 - Its all about the throttle switch today (17)

Austin Healey 100/4 - Learning about the overdrive system and how the different switches tie in. The throttle switch needs adjusting and cleaning.

[@jamiewright1979]

Hi Hugh, I just wanted to let you know that this video helped me out immensely. When i put my 56 110-4 BN2 into storage for the winter last fall '23 the overdrive was working fine. However when i fired it up after winter this year the overdrive solenoid was not engaging. As it turns out it was my throttle switch. After disassembly of my throttle switch and cleaning up the contacts, i have very little resistance, with the switch closed. I am looking forward to reinstalling and hitting the road once again. Thank You for all of your videos through out your restoration process, it is quite inspiring to say the least. Thanks, Jamie

[@trevorparker8686]

That throttle switch is an integral part of early Healey overdrive system, you won't have the benefit of the automatic kick out when when you hit the throttle below 40 miles an hour. Does your transmission have the speed sensor on the back end of the gearbox? Or is it the later BN2 style? Cheers

[@ihealey458]

Hi Trevor - my Healey is late BN1 with the rear 5 stud axle (hypoid) so it does have the centrifugal switch (speed sensor) and the gearbox switch (2 & 3). I've already serviced the gearbox and overdrive and these are ready to install. Cheers Hugh

[@majorscope]

Hi. I was told years ago to connect both wires to one terminal and bypass it. Just dip the clutch when you go in and out of overdrive,. I did this for thousands of miles with no problem.

[@ihealey458]

Hi majorscope - ok - you're bypassing that function altogether and that's fine... I guess... but... you are putting additional stress on the Laycock Overdrive which is not what Edgar de Normanville the inventor recommended. The overdrive was designed as a fuel saver offering a change/reduction in gear ratios at the flip of a switch. It was a time when fuel economy was becoming a priority for automakers and was well received and installed in many models. I've pulled a couple of overdrives apart and with their planetary gearing these units are not as robust as you might think. I would like to aim for originality - it does add complexity and can be finnicky if not fully understood. Thanks for the heads-up anyway Hugh

[@andyamour3420]

Hi, really appreciate your videos and the detail you have shown. As it happens, this months copy of "Rev Counter", the Austin Healey Club magazine has an article by Norman Nock on adjusting the throttle switch. It has a bit more measurement involved. I can send a copy if it helps?

[@ihealey458]

Hi Andy Yes please - that sounds great. I would love to see anything that helps sort the throttle switch mechanism. My email address is [e-mail] Thank you Hugh

[@andyamour3420]

Sure, I'll scan it and send it off tomorrow morning - that's about 12 hours time.