[Healeys] Overdrive relay.

[josef-eckert at t-online.de]

Agree with all Roger said.
 
Josef Eckert
Germany
 
 
 
-----Original-Nachricht-----
Betreff: Re: [Healeys] Overdrive relay.
Datum: 2023-09-18T23:18:22+0200
Von: "Roger Grace" <roggrace at telus.net>
An: "john harper" <ah100tech at gmail.com>
 
 
 
Wonder why you want to replace the original relay ? - they are robust and 
although I have not opened one, the distinctive "click" that the contacts 
make indicates a decent set of contacts.
What is a modern relay ? A typical automotive 30A one with the plug in base 
and connection tails - not much smaller than the original ?
This relay is coil operated so minimal current is required at W2 and W1 (WP 
colour) terminals.
Now regarding the wire what do you mean by thinner wire ? is this perhaps 
22 ga or ?
The issue to be aware of is not so much the wire current rating but the 
short circuit time ability.
The OD relay is fed by an ignition switched white wire W that is unfused 
and sourced directly from A3 at the fuse block.This has the full battery 
fault current (oomph) behind it. So if you are determined to change the W 
wire X section you should install an inline fuse as close as possible to 
the fuse block terminal. A 15 or 20 A fuse would probably be OK. You don't 
want your new thinner wire to become a fuse in the event of a fault.
rg
BTW have made a simplified OD wiring diagram that might make things easier 
....
LMK if you want a copy.

On Mon, Sep 18, 2023 at 2:11 AM john harper <ah100tech at gmail.com
<mailto:ah100tech at gmail.com> > wrote:
  Simon
   
  If you use thinner wire to the overdrive relay it will add resistance to
  the heavy coil and reduce its 'pull' and this might cause a slow
  overdrive engagement. In the limit, it might not even pull the armature
  high enough to disconnect the heavy coil which might then overheat
  including the thinner wire you are suggesting. This might then be a fire
  hazard.
   
  All of this might be the worst case and perhaps I am being alarmist but
  why modify something that worked? They knew what they were doing when
  they originally designed the car electrics.

  On Sun, 17 Sept 2023 at 22:03, Simon Lachlan via Healeys <
  healeys at autox.team.net <mailto:healeys at autox.team.net> > wrote:

    I am putting a modern relay into my OD relay. Done it before with both
    the 8-way flasher box and the OD relay. Works well, though this one
    only managed +/-10 years. 10 years, but not so very many miles…

    Anyhow……it’s a really tight fit in there and I thought I might save
    some space with thinner wires this time. What does the team think about
    the ampage flowing around in there? Is there much and is it constant
    when the car’s in OD or is it just a short burst to activate the coil
    and energize the solenoid? I’m thinking that bigger wires means less
    space (Harder to bend into little spaces) and thinner wires means
    overheating and consequent problems…..

    Simon

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