The first thing to do is confirm whether it is electrical or
mechanical/hydraulic. Connect an ammeter in series with the solenoid as this
is the only way you will confirm that current is flowing through the circuit.
You can check voltages but that only indicates voltage is reaching that point,
not that it is flowing through the solenoid itself.
You say you have a 67. In late 67 the MkII was introduced with the
all-synchro box and the LH OD. This type does not have a relay, only the
earlier MkIs with 3-synchro and D-type OD had that.
If you have the D-type the ammeter needs to go in the yellow/red that goes to
the gearbox lockout switch, at the relay is convenient. You only need to turn
on the ignition and operate the manual switch to check the current flow, you
don't need to be driving. However if it is intermittent you may like to set
the ammeter up in the car where you can see it while driving. Unfortunately
this means that the vacuum switch can bypass the ammeter so you will need to
disconnect (and insulate) the yellow/red at the vacuum switch. As long as you
don't disengage the OD at high rpms with your foot off the accelerator you
will be fine.
The LH-type is much easier, just wire it in series with the manual switch.
If you see current flow (about one amp on the LH-type) when OD is selected but
has not engaged you know the problem is mechanical/hydraulic. If no current
flow the problem is electrical, now use voltage tests to see how far it is
getting. The most dismantling you should have to do is remove the solenoid.
Fo the benefit of anyone else who thinks they may have been wrecking their OD
dipping the clutch or backing off/increasing the accelerator is *not* required
when engaging/disengaging OD, but there is little harm in doing it if you
choose to.
----- Original Message -----
From: Carl French
To: mg list ; MG-MGB
Sent: Wednesday, August 07, 2002 2:43 PM
Subject: [MG-MGB] Evolving OD problem (early OD)
On my 67 with OD which was added in 1980 by a GPO (Great previous owner) I
am having a problem with intermittant working of the OD. It started in June in
Ct while on the 'Dare to be British Weekend' It showed up first as when I
threw the switch in and let the clutch back out (less jarring that way)
nothing happened. Dave Duetsch Mike Robson and other MG experts at the scene
suggested low oil and I checked it and it did appear to be down a pint or so.
I added that and I believe it worked all the way back to Maine. Since then the
problem has been coming back more and more. I had talked with my mechanic
about it and he had first thought it might be the solenoid. Being the
procrastinator I am, I have never bothered to give it to him for a day or two
to check this out as I figured I would get it fixed 'sometime' before Stowe.
Besides I have the 80 project that just wont go away to get out of the
driveway. The problem continued to be off and on for the summer with the usual
symptom being going but then bucking in and out of gear. On a club trip I hit
the switch and heard an noise that I first thought was an electric noise
'snapping, popping' coming from the tunnel next to me. I figured it was the
solenoid shorting and turned it right off (did I mention that I am a
procrastinator?). In the meantime I got the new wiring harness and when I
cleaned the contacts to the OD electrical component on the fire wall (relay?)
it worked great for few days but I think it was just coincidence. The more I
listen to this noise in the transmission tunnel the more I think it is a
mechanical noise of gears not meshing all the way. It is not the loud gears
clashing noise but a softer muted noise like a clacking or so. I have not
given you guys much to go on but any Ideas? does it look like I get to spray
out the engine bay this winter while it is empty?
Carl French
Yahoo! Health - Feel better, live better
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