Chicagoland MG Club: Tech Tips

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Adding Turn Signals

I read with interest an article by Jim Rutledge on adding a hazard flasher to older British cars, and it was certainly a simple, effective solution. It had, however, a couple of disadvantages. One, which was mentioned, is that of a high flash rate. This also has the potential to reduce the life of the flasher. The other drawback is that it requires the ignition key to be on in most if not all, applications. Also the Editor's suggestion for adding fuses should not be needed, as the turn signal circuit should already be fused, and any current flowing through the modification will be flowing through the existing fuse.

I would like to offer another simple solution but without the drawbacks of the first solution. It requires the addition of only one, simple, readily obtainable switch, and a second flasher unit, one specifically designed for hazard flasher duty*.

Purchase a double pole-double throw (DPDT) switch from Radio Shack or any other electrical supply house. Also purchase a flasher from an Auto Supply store. Make sure the switch you buy does not have a "center-off" position, as most switches found at auto supply stores do. For installation (see diagram), simply cut the two wires mentioned in the previous article and insert the switch in between the cut wires as follows.

The wires coming from the turn signal switch should be soldered to the adjacent terminals at one end of the switch-it doesn't matter which end of the switch, or which wire goes to which terminal. It may be necessary to add extensions to the wires, in order to reach the switch depending upon where you situate it.

The other ends of the wires go to the adjacent terminals in the center of the switch. The only requirement here is that the colors match on each side of the switch. The two terminals at the other end of the switch should be soldered together with a short length of wire, and a second length of wire soldered between these terminals and the output terminal (marked L) of the flasher.

The input terminal of the flasher (marked X) should be connected to any purple wire (or any wire that is fused and hot at all times, with or without the key being on. In most British cars this will be a purple wire). If you use a purple wire you shouldn't need a fuse. If you prefer, connect to a brown wire and insert a fuse of 10 amps as close to the brown wire as you can. Of course, all the normal cautions of wiring should be heeded.

If you would like to get really fancy, buy a three terminal flasher and connect an indicator light between the third (marked P) terminal of the flasher and ground. Position the light wherever it is convenient for you, and now, when using the hazard flasher, the indicator will flash just like your father's Oldsmobile!

* The difference between a turn signal flasher and a hazard flasher is this: A Turn signal flasher is designed to operate only under one specific load condition. If a turn signal bulb is burned out, the flasher will not flash. This is a safety feature designed to warn you of a burnt out bulb so you can replace it. A hazard flasher, on the other hand, is designed to operate no matter how many bulbs are burnt out! This too is a safety feature. Under any condition you might be using the hazard flasher, it is more important that whatever bulbs are working are flashing. The lights are needed now! Many of the 'heavy duty' turn signal flashers sold are, in reality, hazard flashers.

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