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MG MGB Technical - Hazard Flasher Switch Change

To update you... I have a 68 roadster but changed the dash over to a metal dash. Lots of work, but well worth it IMHO. The hazard switch on the 68 is a huge rocker switch and just did not go with anything, so I simply did not install it in the dash and just let it sit on the gearbox tunnel. This was the last project for the interior except finding and installing a radio.

I tried to find a double pole double throw toggle switch that matched the metal dash toggle switches but no joy. I looked all over the WEB, called several companies and even e-mailed pictures of the switch to see if they had anything. I even went to Radio Shack. They had a switch but with the help from this board, I decided not to use it as had possibilities of not handling the amperage

I then tackled the job using 2 5 pin Bosch relays with the 87 and 87A pins again as described on the board. What a joy. The lamps work wonderfully and I now have a switch that matches the rest of the car.

Because the gearbox tunnel is wider on the 68 vs 67 and older models, I had to make a new consol. I got some sheet metal and bent it to match the width of the original 68 consol but taller to fit the metal dash. I then covered it in vinyl and installed it. It looks almost OEM. From there, I put holes in it for a toggle switch for the hazards, a small hole for a red indicator lamp for the hazards and a cigar lighter to power the I-Pod/accessories. These are installed and now, I don't have a gaping hole below the dash.

Thank you to all who helped get this part finished. Especially the electrical wizards who take the time to make easy to follow directions and drawings for the rest of us.

Cris
Cris DeYoung

Hi Chris.

Thanks for the update, it is always good to hear how a problem was resolved.

Don
Don

Hmmm, I have exactly this problem and it sounds like the solution you have it what I came up with the hard way. I know now to look back through the archives and see how you did yours.

Mine is a 78B that I am fitting an earlier style steel dash into and I want to use a simple toggle for the hazzard switch. I also need to do a custom centre console (I was going to make one from fibreglass maybe).

Cris, do you have pictures of yours you can send me and a circuit diagram of how you wired up your hazzards please?

Thanks!

Simon
Simon Jansen

Simon,

I'll pass on the data to you. It will probably be this weekend before I get to it. I can't take credit for any of the ideas for changing the switch. I got all of it from here. I'm just glad it works.

Cris
Cris DeYoung

Cris. Many thanks for letting all of us know. All of us learn from each other. The lessons I have learned here far exceed what I had been able to learn over the previous 30 years. The people here have been a blessing.

There has, however, been one problem. A major one from my position. Often, when we, as a group, provide our ideas and test methods, people correct the problem and never bother to let us know what actually worked.

Your taking the time to tell us what you found (and very well stated) and how you handled the problem is greatly appreciated.

I provide information here and through my website. When people bother to respond to what I have posted, or write back to say "thank you" I get a special feeling--I have helped someone who shares my enthusiasms, they have found what limited help I can provide useful, and are of the quality of person to bother to inform me of how they have done. I do not believe that I am alone in getting this "warm feeling" when someone bothers to write back and say, "thank you--it worked and this is what I did to make it work". We all learn from such shared experiences.

Thus, Thank You for taking the time to post what you have learned. As Simon notes, it may, also, be of interest to other people. Myself included. When you send the information to Simon, please include my website email, les@custompistols.com on the message.

Les
Les Bengtson

If you can find a relay with two normally open contacts where at least one side of the contacts are isolated from each other it makes for a much simpler job than two single-contact relays. However whichever way you wire them you *must* ensure that the turn flasher is isolated otherwise it is possible to have the fuel pump and ignition powered when the ignition is off and the keys in your hand. One way to achieve this is to use a double-pole double-throw switch, with the wires from the lamp units connected to the common connections on the switch. Two wires from the 'normally closed' contacts are then taken to the two wires from the turn switch, and the two 'normally open' contacts connected together and taken to the load side of the hazard flasher.
Paul Hunt 2

Hello,

This is from memory, so maybe not too reliable, :)

The 2 relays allow you to keep the same basic setup of your wiring. There is no additional power used except to operate the relays.

For the turn signals, I disonnnected the wire at the place where they connect to the double bullet connector for the front and back and ran the wire to the 87A contact on the relay. Do this for the left and right side. Each relay operates one side of the car. This is the always connected termal of the realy. I then ran a wire back to the double bullet connector from the 30 terminal. This simply lenghtens the wiring for the turn signals by about 6 total feet.

For the hazard switch it is a little more complicated. Thus the memory problems. The original hazard switch has 2 solid green wires. They are simply disconnected from the switch and then connected together. This completes the power source for the turn signals. I believe this wire is switched by the ignition.

Next, there are the wires for the flashers for left and right side of the car. I disconnected the wires and had to change the spade connectors to a larger connector. I then connected these to the relays, making sure I connected the correct side to each relay. (I don't think this really matters but I just like a neat set-up.

The last connection is power to the relays. I ran a wire from an un-used (purple) wire under the dash through the toggle switch to the 85 terminal of both relays. The purple wire is always on and the toggle switch operates the hazard lights. I then connected both 86 terminals to ground. The old hazard switch had a large grounding wire with a spare section of a multi bullect connector available.

That allowed the hazards and turnsignals to operate independent of each other and kept the power supply the same as original to the circuts.

The last thing I did was shorten the wires for the Brown (hazard power, fused), and others to make the connection a little cleaner. The entire original hazard switch separates from the loom with bullet connectors. The last thing I did was to change the indicator bulb to a smaller light that still matches the dash. I got it from an electrical supplier, the light is an LED with a red cover.

I zip tied all the wires together and tucked them under the console cover.

I'll send pictures to all who request them this weekend along with the wiring diagram I received from this board.

Cris
Cris DeYoung

I think the way I was going to do it was with one SPDT relay to switch power to a single flasher unit. The NC contact goes to the switched power side of the ignition. The NO contact to the fused always on side. The common goes to the flasher. Then I use another two SPST relays which effectively short out each side of the indicator stalk switches so each side of blinkers now connects to the bulbs.

I can use just one flasher which is load independent so it works fine as a indicator flasher with one side flashing or a hazzard flasher with all of them flashing. I can also use a simple SPST switch for the hazard switch. So all up one flasher, three relays and a simple switch (my logic being relays are A LOT cheaper than flasher units).

I am actually using a standard Lucas 2 position toggle on my dash with the first position switching on the map reading light on the dash and the bottom position to turn on the hazards.

Errr, I think. I haven't wired any of this up yet to see if it works!

Simon
Simon Jansen

Simon,

The two relays work very well. When you turn on the power, the 87A terminal disconnects and disables the stalk turn singal and turns on the hazard flashers. Quite simple actually after I studied the drawings for about 2 days to see exactly how to wire it together. I'll get the pictures to you this weekend then it might be a little more clear. As I said, it took me a while.

Cris

Cris DeYoung

Let's see some pictures!
Greg Bowman

Cris, pics would be great. I need to sit down with a bunch of relays and parts then I'll be able to see exactly how you mean. So you only use one flasher unit?
Simon Jansen

Hello, I just sent an e-mail to those of you who included your addresses. It has the wire diagram. This came from Dan Masters. He posts here ocasionally, but I haven't seen him here recently. So if he is out there, Thank you again Dan.

The pictures will be on their way this weekend./

Cris
Cris DeYoung

"I can use just one flasher which is load independent so it works fine as a indicator flasher with one side flashing or a hazzard flasher with all of them flashing"

This is a safety hazard. The reason why the two flasher units are quite different (they are if you didn't know) is that all turn/indicator flasher units are designed to flash two bulbs only, and to give an indication by a change in flashing speed if one of the bulbs has failed. In the era of our MGBs the bulb failure mode is to stop flashing, so the good bulb glows constantly. Modern flasher units flash the remaining bulb at about double-speed, which unfortunately some people are too stupid to notice.

By contrast the hazard flasher is designed to flash anything from one to four bulbs (any number may have been damaged as a reult of an accident), and for a long time running from a slowly reducing battery voltage.

The other difference between turn/indicator flasher units and hazard units is that for the former the lights glow immediately the switch is operated, pause momentarily, then begin flashing off-on-off-on. Hazard lights generally do nothing immediately the switch is operated, then after a pause begin flashing on-off-on-off.

Some after-market turn/indicator flasher units are described as 'heavy duty' but are little more than hazard units as they flash regardless of how many bulbs are operating. As I say, with one bulb out this is a safety hazard, as you do not know when one of your lights has failed when slowing to turn across the traffic, and neither does that artic bearing down on you.
Paul Hunt 2

After Pauls comment I went and had a look at my parts shop and got a 12 volt flasher with the blown bulb indication. On it it says 6 x 21W + 5W. Not sure what the 5w is?
Simon Jansen

Ah, dashboard indicator light I guess.
Simon Jansen

6*21W means *six* 21W bulbs and hence unlikely to have the blown bulb indication, test it first. Should say 2*21W. The 5W is probably a wing repeater, dash bulbs are about 2.2W.
Paul Hunt 2

This thread was discussed between 14/03/2006 and 19/03/2006

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