Some years ago, Lucas changed the plunger material from brass to plastic.
After this change, it was fairly common for the plunger to mushroom over
time, effectively shortening the plunger, and preventing the switch from
closing. This causes the high current to remain engaged, and leads to
failure of the solenoid.
Given the high price of these solenoids, and the fact that most failures
are due to continuous engagement at the higher current, I wonder whether a
simple solid-state timer could be fabricated, to take over this function?
Are there any EE types out there who would like to tackle this one? :-)
-mg
----------
From: Scott St. Clair[SMTP:scott_st_clair@C-Cube.COM]
Sent: Thursday, September 07, 1995 3:54 AM
To: Triumph list
Subject: FWD>RE>2 More questions
Mail*Link(r) SMTP FWD>RE>2 More questions
Egil is right. The A-type overdrive soleniods have a two part coil: a
powerful one for engaging and a weak one for holding. When the soleniod is
not powered and the OD is disengaged, the plunger in the soleniod allows a
contact on top of the soleniod to close (it's under the black rubber cap).
This contact connect the power coil to the +12 volt input to the soleniod.
When the soleniod is switched on, the plunger is pulled up, engaging the OD
and opening the contact. With the contact open, only the weak coil is
energized, but it is enough to keep the OD engaged. When you switch off the
current to the soleniod, the plunger falls, disengaging the OD and closing
the power coil contact.
This contact is very like the points in a distributer. They burn and fail
to
conduct electricity. Talk the black rubber cap and the little white plastic
cover underneath it off the solenoid to expose the contact. Use very fine
sandpaper (320 grit) to clean the contacts and put the whole thing back
together. It'll work fine.
Scott St. Clair
'68 TR250
--------------------------------------
Date: 9/6/95 11:46 PM
From: Egil Kvaleberg
In article <950906171624_92738968@mail04.mail.aol.com>, JMardy@aol.com
wrote:
> 2) My overdrive solenoid needs a push to engage. It doesn't have enough
> power to engage the OD. On the bench without a load, it seems strong.
The
> actuating shaft on the OD doesn't have very much resistance. Is the
solenoid
> just worn out? Can a new plunger be purchased or do I have to spend $110
on
> a new solenoid? Can the body of the solenoid be sleeved with something?
Is that an 'A' overdrive? The 'A' has two coils, one high current for
engaging, one low current for holding. A contact within the solenoid
disconnects the high power coil when the solenoid is fully engaged.
Use an Amperemeter and check the current consumption (the exact figures
should be in the book).
Egil
--
Email: egilk@oslonett.no Voice: +47 22523641/92022780 Fax: +47 22525899
Snail: Egil Kvaleberg, Husebybakken 14A, 0379 Oslo, Norway
URL: http://www.oslonett.no/home/egilk/
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From: egilk@oslonett.no (Egil Kvaleberg)
Newsgroups: mail.triumphs
To: triumphs@autox.team.net
Subject: Re: 2 More questions
Date: Thu, 07 Sep 1995 07:05:31 +0200
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