If you have a universal ISO relay (ice cube size) then it is improbable that
it is an original fit. Maybe a previous owner had added extra loads to the
accessory circuit and was getting too greater voltage drop. Adding the relay
would have solved the problem. I may be wrong but I don't believe the ISO
standard relay was around in '77. If it is that type not only would Bosch
fit but also almost any relay from any maker around the world.
----- Original Message -----
From: Steve Murphy <email@example.com>
To: MG List <firstname.lastname@example.org>
Sent: Tuesday, December 21, 1999 5:08 PM
Subject: Ignition warning lamp solved!
> Well, I found the reason for my glowing warning lamp. My car is
> different from the Haynes diagram which should apply to it, or I'm looking
> at the wrong one, or something. According to what I've seen, the ign
> switched accessories should be fed through the fuse box via the white
> On my car, the white wire feeds the field coil of a relay which switches a
> white/brown wire (going to the accessories terminal of the fuse block) to
> the brown battery buss. At some point, this relay had failed, and the PO
> (probably going by the same diagrammes that I was) "repaired" the problem
> jumping the white wire directly to the fuse block. Since this wiring
> "stiff" enough to handle the current demands, the voltage sagged, causing
> the indicator to glow. Replacing the defective relay and repairing the
> wiring cured the problem.
> I had some Bosch automotive relays on hand, so I used one of those,
> was quite surprised that the pin-out was identical to the Lucas, even down
> to the numbering of the pins!
> Now I'm wondering if there is an appropriate schematic of the wiring
> my car (77B) in perhaps a later Haynes manual? Mine is c1977, and none of
> the diagrammes show such a relay... they all show the wiring going to the
> fuse block directly from the ignition switch.
> BTW, when splicing wiring where it can be exposed to the elements, I
> crimp and solder the connection, dress it with "liquid tape", then cover
> with heat shrink. I've used this in marine applications and it works
> never had a failure.
> Thanks to those who replied to my previous post, I truly appreciate
> Steve Murphy
> 77 MGB