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Ten Hands-On Tech Tips

Ten tips for when working on cars

by Julian Edgar

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At a glance...

  • Cleaning solvent
  • Cheap high-temp insulated wire
  • Crash safety of under-dash additions
  • Keeping fasteners
  • Cheap trickle charger
  • Pressure gauges
  • DIY electrical high current eye terminals
  • ...and more!
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This article was first published in 2005.

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Until recently, whenever I’ve wanted a solvent to clean off grease – or to just clean a part – I’ve used petrol, meths or kerosene. But then I bought a container of ‘grease and wax remover’... and now I use it on nearly every heavy duty cleaning job! From cleaning off the oil on a set of new brake discs, to wiping over metal parts before painting with a spraycan, to removing greasy smears from the inside of door jambs or cleaning surfaces before applying double-sided tape – it’s worked superbly. It’s available from shops selling automotive paints.

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Here’s something that’s very seldom thought of – but it makes lots of sense. When installing components under the dashboard (anything from an alarm module to a new ECU), it pays to think of what would happen in a crash. I was recently installing a folded sheet aluminium bracket to hold an electronic module in place, when I realised that the original design of the bracket would have a thin, sharp edge directly facing the front seat passenger. Of course, being buried inside the dash it was hidden from view, but if the dash had been pushed towards the passenger in a crash, that knife-like bracket was in an ideal position to slice them. In this case the simple answer was to fold-up a wide lip on that side of the panel.

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If you’re organised, you can save yourself a lot of time and frustration. One easy part of that organisation is to keep all fasteners that you come across. So if you’re bought a car part from a wrecker and it has bolts, screws or nuts that you don’t need for the project, don’t throw them away but instead remove them and place them in small containers. The high quality bolts that you salvage in this way are almost impossible to readily buy (eg the ones with captive washers) and if you’re working on just the one make of car, you’ll find that many of these salvaged fasteners are a direct factory fit in other car applications. That is, the bolts will have the same threads, same typical lengths, same socket sizes, and so on.

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We’ve covered it before in detail at Zero Cost Trickle Charger, but it’s worth repeating here. If you have a need for a small trickle charger ("trickle" meaning that it’s the sort of charger you leave attached for a few days in order to bring up battery voltage), you can make one for just a few dollars. All you need is a nominally 13-15V plugpack (wall-wart in the US), a resistor and a few alligator clips. That’s all! With many people throwing away plugpacks, it’s a no-brainer to source a suitable plugpack for nearly nothing (secondhand stores, the tip, kerbside collections, etc) and then the rest is simply so easy. Since the original article was written, I’ve now built three of these chargers – right now, one is charging a spare 12V car battery, while another is charging my electric bike batteries.

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Pressure gauges use technology that hasn’t changed in 50 years. A curved tube inside the gauge (called a Bourdan tube) straightens under the influence of pressure. The tube is connected by a gear mechanism to a pointer. This lack of technological change makes an old pressure gauge just as useful as a brand-newie – so long as the old one is in working condition, of course. Recently I sourced a boxful of old gauges (they were bought at a household goods auction – cost of the box, AUD$12) and in it were two gauges useful for automotive applications. One is a compression gauge and the other a calibrated and marked vacuum gauge – that’s the one shown here. Check our article on Using a Vacuum Gauge for Engine Diagnostics and remember, always look with close interest if you see secondhand gauges cheaply on sale.

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Most insulated electrical wire has a low temperature rating – at anything over about 80 degrees C, the insulation covering starts to soften and melt. High temperature rated cable is available – but only from specialist suppliers and at a tall price. But if you have a need for some high temperature insulated wire (eg when the wiring has to pass close to the exhaust), short lengths can be easily got for nothing from junked stoves and hotplates. The wiring is rated up to 150 degrees C, and uses silicone insulation or high temperature sleeving. The current rating is also quite high – this is good quality wire! In many cases, spade terminals will already be crimped to the cables.

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Every now and again you’ll have a need for hefty electrical eye terminals – the sort that have enough current capability to work with battery cables. It might be because you’ve moved the battery to the boot, it might be because you need a new earthing strap, or you might just be wiring-in an ammeter or high power amplifier. In all cases, if you’re stuck for terminals, it’s easy to make your own. All that you need do is select a piece of copper tube that has the right internal diameter to match your cable. Cut off a short length of the tube and then use a vice or a hammer to crush one end flat. Round off the sharp edges of the crushed end with a file and drill a hole through that end. Hey presto, one heavy duty lug terminal!

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Whenever you’re shopping, keep an eye out for goods that can be turned to alternative, automotive uses. This coat hanger is available in a bunch of five for about five bucks. So, you don’t want any coat hangers? Well, think again. The hanger is constructed from beautifully bent 8mm thin-wall stainless steel tube! Cut the coat hanger up with a hacksaw and you have five bends (ranging from 180 to 90 to 30 degrees) and several straight lengths of stainless steel tube. They’re just the things for squeezing turbo wastegate or vacuum line plumbing into tight underbonnet spaces – the bends are much tighter than you’d readily achieve with hose alone.

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While it’s very common for modifiers to use sheet steel and aluminium, you rarely see them using plastic. That’s a pity because plastic sheet is easy to cut and bend (to do the latter, heat it first) and is often better in certain applications than metals. ABS is a tough and resilient plastic while acrylic is available in a range of colours, including clear sheet. The best approach is to find a company that uses the plastics to manufacture goods and then approach them in search of off-cuts. Some recycling organisations also have plastic off-cuts available. The cover for the circuit breaker mounted on the outside of the battery box was made from an acrylic off-cut.

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If you look around at any place where junked consumer and automotive goods can be found, you’re sure to see some printed circuit boards with excellent components still intact. For example, the other day I came across a Bosch ABS controller that was being chucked. On it was a heap of components. Although most were not usable for someone with my level of electronics knowledge, there were also four high quality 12V miniature relays. Relays that would be perfect for lots of uses! However, if you’ve ever tried to unsolder multi-pin components, you’ll know how hard it is to do this without stuffing the component. But there’s a very easy answer – aim a heatgun at the solder side of the board and after a few moments, the component will almost drop off! At the most, all that will be needed is a slight wriggling with a pair of pliers. One of the relays salvaged from the ABS controller can be seen here, being made use of in a completely different application.

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