Soldering

[insanitybeard]

Just a query for you experienced solderers out there.....

(forgive my ignorance if this is -or should be- common knowledge!)

Do you use a flux when e.g carrying out repairs to wiring looms- splicing in new bits of wire, remaking bad joints etc? If so can you recommend a good product for this purpose? I have carried out soldering before, not just in the context of cars, but nobody in my automotive training made a point of stating that flux should be used to avoid weak solder joints or just poor quality workmanship.......

Any thoughts?

[Mirez]

Well flux is there to help the solder flow and nearly all solder reels you buy will have some flux in it (the reason it smokes). This on its own should be more then enough for 95% of soldering jobs you are likely to do automotively. The only reasons you may need additional flux is if the wire/joint to be soldered is in a poor state (in which case flux may help the solder flow a little better) or the wire to be soldered is extremely thick (amp cable for example) where the additional flux will help pull the solder into the cable. Its no substitute for proper cleaning and preparation of the cable though and tbh, I can only think of one occasion I've needed it in the last 10+ years of soldering!

[Chrispb]

The cored solder reel I have is donkeys years old but I must admit I always dab on a small amount of flux, the same stuff you use for plumbing rightly or wrongly it always makes the flow easier.

[gregers]

ive got 3 soldering irons,a kit with a 'turbo' jobbie and the normal long one.and ive struggled everytime to use them with the enclosed solder.i:e getting it up to the required temperature.
as i had to repair my rear hatch wires i decided to use my cordless gas iron,and i found sitting on the shelf a roll of thin solder and for the 1st time i done the job instantly without any nightmares.so im goner use this all the time now.flux is used to draw the solder in to run deeper throughout the wires.

[insanitybeard]

Thanks for the thoughts guys, like I say I've carried out solder repairs before on car wiring (without using flux) without problems but I went to try to solder in a couple of new auxiliary water pump carbon brushes recently and just couldn't get the solder to flow at all..... the braided copper cables did look a bit oxidised to be honest but how do you prepare them? Being braided they're not exactly easy to clean, hence me wondering if I should have used some flux. Maybe the solder I bought from Maplin wasn't fantastic and didn't help.....

[bigjeeze]

When I was taught soldering - I was told to always try ( if possible) to "tin" both items before joining.  obviously flux can help in nay case but to tin first really ensures a really good connection/joint.  This applies to plumbing as well as electronics.

[Mirez]

Absolutely, both sides of the joint should be pre-soldered before the main solder attempt lol

If the copper is oxidized then you have no hope of getting solder to stick to it. On single core cable you can use some wet n' dry to clean the end but on multistrand or braided cable then that's not possible - I normally dip it in an acid solution which cleans it perfectly and very quickly but have had success using this technique as well > Link

[insanitybeard]

A very good point about 'tinning', and one which I had been taught but had forgotten in the few years since I last used the technique (not as a vehicle 'technician', I was taught by a very clever man I used to work with in a shop which restores antique clocks and barometers, we were often using soft soldering to repair old and damaged brass components etc, and we always used flux and a mini blowtorch for that!)