MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Hazard Switch Replacement

I remember reading somedtime ago on this site where someone suggested replacing the Hasard switch with a simple simple double pole single throw switch. Does that sound posible to anyone and how would you wire it??????
Bob R.

Bob,

That might have been me. It takes a simple DPDT "ON-ON" switch. I can send you the details if you'll give me your e-mail address.
Dan Masters

Great! E-MAIL mgbob70@yahoo.com...
Bob R.

Hmmm, the hazard switch also *disconnects* power from the indicator flasher when the hazards are on. If this is not done it is possible to have the fuel pump and ignition powered even though the key is out of the ignition. A DPDT on/on will work the hazards themselves, although not the hazard tell-tale if you have one of those in addition to the right and left indicator tell-tales.
Paul Hunt

Bob,

I'll draw up a set of instructions with schematics and send them to you tomorrow or the next day.

Paul,

You are absoutely right about the need to disconnect the power to the TS flasher when the hazards are on, and my scheme with a DPDT switch does that (or the equivelant of that). The hazard tell-tale may or may not remain functional, depending on which year we are talking about, but it's not mandatory as both the R & L TS indicators will flash, which provides all the indication required.

I've been using this scheme in my TR6 for almost 15 years now.
Dan Masters

Dan - I'd like a copy for my own interest. The description of 'DPDT on/on' confuses me as 'DTDT' to me means double-pole double-throw or 'two switches each with a break contact, a make contact and a common contact' whereas 'on/on' to me is a DPST i.e. double-pole single-throw or 'two switches each with a make contact and a common contct'.
Paul Hunt

Paul,

DPDT is not a complete description of a switch, because it doesn't include a description of the number of positions. Your description of a DPDT switch is the same as I see it (in the engineering world, it is often refered to a two "form C" contacts, which I think is a bit more descriptive - "A" being a normally open contact, and "B" being mormally closed, with "C" being a pair of each with a common center contact).

My understanding of a DPST switch is two form "A" contacts, but with no common point, ie, you turn on two circuits at the same time, with the same handle, but there is no interconnecting between the two. YOu can get DPST switches as you describe, but they have to be specified as such, and are rarely, if ever commonaly available off the shelf at most stores, at least here in the states.

In the world of automotive switches, it is VERY hard to find a DPDT ON-ON switch, they are almost exclusively ON-OFF-ON instead, allowing you to switch between a pair of items or have both off. With a DPDT ON-ON switch, you can select which of two items are on, but you don't have the option of not having either on - one or the other will always be on. In the application we are talking about, we have the option of having the turn signals on OR having the hazard flasher on, but NEVER both at the same time.

It's taking me a little bit longer to get the info out than I had planned, because there are 3 options (for US cars - I haven't looked at other market cars yet) and I want to do one set of instructions to cover all 3, and I want the instrucitons to be detailed enough that anyone, electrically knowledgable or not, to be able to follow them.

However, for your information, as I know you are an electrical expert and will need no extra help to understand, I am sending you a copy of something I did a while back to explain my circuit. As I said earlier, my design doesn't cut power TO the TS flasher, but it cuts power FROM the flasher, which is just as effective in preventing back feed.

Regards,

Dan
Dan Masters

Thanks Dan. I did wonder if you had it connected to the 'output' of the turn switch instead of the 'input' but still needed to clarify the terminology.
Paul Hunt

This thread was discussed between 10/02/2005 and 12/02/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.