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MG MGA - Flash to Pass Optional Extra - Relay Location?

Do any of you out there have the little known option:

"Flash to Pass" - Headlight flasher switch

I think the relay is either fitted in front of the heater or behind the dash somewhere. Behind this dash will obviously differ from LHD to RHD cars.

If you think this was installed by the factory, can you send in a photo of where your relay is mounted please?

Many Thanks
Mark Hester

steering wheeld out on an original one on the UK e-bay website that was listed earlier this week.
I have looked today but it appears to be gone along with its matching relay. I have never seen one advertised anywhere before, but I was still shocked at the price, I seem to recall somewhere in the region of
Colyn Firth

This is the link to the one which I think Colyn mentioned. Only 75
J Bray

Mark, From the SPL, the image of the relay is dotted which suggests that it should be on the engine side of the firewall in a horizontal orientation. There is a picture in Clausager of a red twin cam that has it mounted in front of the heater. The relay is apparently supposed to have a black cover with a Lucas imprint - it would be interesting to see one.
M Wellard

I have wired a simple flick switch into the main beam wiring (fused power supply) which flashes the headlights. I have not fitted a relay as took the view that the few seconds of use should be OK.I had a spare switch orifice that the PO left next to the Speaker panel which was ideal. I have also fitted an electric washer flick switch to replace the push pull manual switch (again fused through my extra 8 gang fuse box)) I also added a buzzer to the indicator warning light circuit to remind me to turn off the indicators as I have tightened the indicator switch to stay on rather than the stupid timed idea which always turned off too soon.
The buzzer and flick switches are cheap from Maplins and all can easily be reversed if required
P D Camp

Many thanks for the eBay link J Bray.

Interesting it quotes my car on how to fit it and I've not even fitted it yet !!! Chicken and Egg on thinks.

I'm getting the sub harness made here in Perth:

Mark, I see what your saying about the Lucas plastic cover. I bet these are very hard to find. but I will ask Peter Wood today.

This relay shown above has 4 terminals and the one on eBay (attached) and mine only have three terminals.

I'll try and get a clearer photo for Barney's site soon.

Still not 100% sure where to mount the relay though, as my bulkhead does not appear to have matching holes.


Mark Hester

Hi again Mark,

If you have info on the sub harness, as used originally, could you please send some measurements (colours, length and route). I am also interested in a black plastic cover if you come across a second one.

The ebay relay that I have also has 4 terminals. I think two are joined so three may be OK.

Cheers, Mark
M Wellard

Yes lots of info.

email me offline and I can send it to you.

I spoke to Peter Wood today and he had not seen the Black plastic cover type relay before.

Please post a photo of the relay you have?

Mark Hester

The 4-terminal relay (factory original type) does not have any common terminals. See here:

Terminals C1 and C2 are the primary contacts for power switching (interchangeable). Terminals W1 and W2 are the coil terminals (interchangeable). This way the power wire (C1) can be always hot, while the coil input (W1) can be connected to the switched fuse so it will only operate with ignition switch on.

A 3-terminal relay could have one of a couple different internal circuits. It may be that C1 and W1 are on the same terminal, and grounding W1 will switch it, in which case it will work with ignition off. Or possibly W2 might be grounded to the case, in which W1 will require power input to switch it.

It is possible to convert a 4-terminal relay to 3-wire operation. You can connect C1 and W1 together to make it operate without the ignition switch. Or you can ground W2 to make it operate with trigger power input.
Barney Gaylord

This thread was discussed between 10/11/2011 and 11/11/2011

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