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Re: Overdrive jumping out

To: healeys@autox.team.net
Subject: Re: Overdrive jumping out
From: mike brooks <hypercubic@yahoo.co.uk>
Date: Mon, 17 May 2004 23:56:43 +0100 (BST)
Hi, Simon and Dave,
 
I just had to look at mine on my BN2. I agree with Dave that the problem is not 
the throttle switch directly. The reason I say this is that all the throttIe 
switch does is to hold in the contacts C1 and C2 at low revs, with the O/D 
switch off. The overdrive relay has to energise first in order to initially 
close C1 and C2.  IMHO it must be a wiring error for the O/D to come in at all 
without the overdrive relay coil energising. If someone has bypassed the O/D 
relay such that the power goes  to the O/D solenoid via the throttle switch 
only, this would give the symptoms you describe [although I think 1900 revs is 
too high for the throttle swich opning setting -shouldn't it be about 1/5th 
throttle?]
 
I added this in the hopes it would hlep rather than confuse!!
 
Best regards
 
Mike
 
 
Date: Sun, 16 May 2004 11:09:04 -0600
From: Dave & Marlene <rusd@velocitus.net>
Subject: Re: Overdrive jumping out

Hi Simon,

I don't remember which model car you are having trouble with. If it is 
a 
BN2 or later this will apply.

It appears that the solenoid is being controlled by the dash selector 
switch plus throttle switch only -- that the OD relay is not 
functioning 
due to a relay problem or wiring problem. Either the relay coil 
connected between W1 & W2 is not operating or the relay contact between 
C1 & C2 is not making contact. I am attaching a schematic drawing with 
explanation of how the circuit works. This list will remove the 
attachment for all other recipients.

  Operation of the relay coil can be checked by applying 12 volts to 
terminals W1 & W2.  If the coil operates, there should be solid 
continuity between terminals C1 & C2.  The relay itself can be opened 
by 
removing it's cover. The contacts can be carefully cleaned. Or the 
relay 
itself may be defective & not repairable. Any problems other than the 
relay will likely be loose connections, broken wires, or mis-wiring.

Dave Russell
BN2

Simonlachlan@aol.com wrote:
> Hi, I am back from a short break and have yet to apply myself to the  
> overdrive issue. See below
> ""One for the gurus....
> Background first:-
> I have all new overdrive  mechanicals which worked fine until just 
recently.
> I have a 28% ratio o/d  unit.
> Plenty of good clean oil in gearbox, first thing I  checked.
> Overdrive on/off switch is new and works fine.
> Switch on  gearlever is not new but works fine.
> I have not messed around with carbs or  related linkage.
> Solenoid sounds healthy and engages overdive firmly.
> (I  have a 3:54 diff, so the revs may seem a little low to you, 
especially 
> coupled  to a 28% o/d)
> 
> So, the symptoms
> If I am driving along at about  1,900revs with my car in 
overdrive/4th, 
> she'll jump out of overdrive if I raise  the revs/speed with the 
accelerator.
> If I then decelerate back to 1,900 (+/-)  she'll pop back into 
overdrive.





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