Rheostat Light Switch

[Rod]

Hi All,

I thought i would share my experience on these with you all and how easy they are to repair. As you know to find a switch with a rheostat still functional, not faulty is getting harder and harder. The rheostat controls the dimming of the dash lights. A number of years ago  I repair one with limited success. All I did was solder the broken end of the resistance wire to the post it had broken away from. I say limited because the space between the coils was inconsistent and hence the dimming was inconsistent.

Anyway I thought I would have a go at repairing another yesterday. What I did was the following:-
1. Removed the switch knob by holding button at rear of switch while pulling out knob assembly.
2. Removed the front section of the switch (the U section).To do this I turned the switch upside down and dremeled the edges of the flange off and then tapped off from the main body. Removed the rubber section between the U and front of switch.
3. I then opened up the U to get better access to the resistance wire (only enough to get access).
4. Removed the contacts.
5. Removed the resistance wire by cutting off from the one remaining attached end.
6. Inserted electrical wire up the coiled resistance wire and rewound accordingly to get proper spaced windings. Removed electrical wire carefully to maintain spacings.
7. Reinserted resistance wire into ceramic recess of switch and soldered to the contacts.
8. Inserted contacts.
9. Replaced U section and reflanged on the underside with a punch making sure the front rubber section was in place.
10. All Done.

I have since done another one and I am happy with the end result. I am sorry but I didnt take any photos so I hope the above description maybe of use to others. This process will only work if the resistance wire is still within the switch and broken from one end. I have seen some switches where the wire isn't present.

Cheers

Rod

[Martin]

Rod, definitely sounds like a good fix.  A couple of questions:

1.  How brittle is the resistance wire?  If you're ham-fisted (like me) what chance is there that it will break even more?

2.  If the break is half-way down the wire, could it be rejoined by a careful solder, with the join being re-inserted on the "down" side?

I've got an old switch to have a practice on - might give it a try.

Thanks for your guidance

Martin

[TTV6FC]

Actually Rod,I'm surprised that you said you were able to solder the wire back on.  Rheostat wire is made of Nichrome which is how it attains it's resistance.It is also a hard steel and solder will not take to it which is why it is riveted.I have tried to solder Nichrome when I was a young apprentice almost 20 years ago and the boss looked at me like I was an idiot then told me the story.Maybe the solder is sticking to the rivets you are using.In some cases solder will completely surround a metal and look stuck?I'm always learning though so I could be wrong. Cheers,Jamie.

[Rod]

Martin,

When I played with the wire it didn't seem to brittle. Of all the broken switches I have seen the wire has been broken right at one end. As for soldering in the middle I am unsure. Maybe Jamie's explanation would indicate that its not possible.

Jamie your reasoning on the soldering seems correct and reasonable to me but I used a pair of tweezers to test the joins after the soldering.I couldn't seem to budge the join. I will test the resistance with a multimeter after I log of to see if the joins are ok. I assume time will tell if this is successful. The one I did years ago hasn't failed even though the success of a consistent variable dimming wasn't successful due to inconsistent spacing between the coils. I suppose if doesn't work in the long run it has only cost me time.

Cheers

Rod

[TTV6FC]

Anything to be able to reuse or repair these mechs is a bonus.As I said,if it works,that's great news.I think it would be far less likely that it is possible to join them in the middle though.Thanks for the repair details.Cheers,Jamie.