Nobody gives their wiper motor much thought until the blades stop swishing back and forth, leaving you stranded in the pouring rain, unable to see through the windscreen.

First published in the March 2008 issue of Street Machine

Wiper systems can last for decades with no maintenance other than occassional blade replacement. However, like every mechanical component, reconditioning or replacement is inevitable. If yours is an electric type, then it’s possible to rebuild it. If it’s an old vacuum-driven system, it’s probably a good idea to upgrade to one of the many aftermarket electric systems.

Aussie motoring manufacturers regularly swapped between Preslite, Bosch and Lucas wiper motors. That said, the vast majority were manufactured by Preslite. This is a bonus as the Preslite is a fairly robust unit that usually gives few problems.

The unit featured here is typical of the type fitted to pre-HQ Holdens. However, the same basic wiper was used on Holdens from about the mid-60s (HD) right through to WB and mid-generation Commodores. Similarly, Fords (up to about EL) and Valiants (through to VH) used the same generic unit.

Although it underwent design upgrades, the Preslite system remained essentially the same, so many parts are interchangeable. This means that rebuilding one from assorted secondhand motors is quite achievable. Unfortunately new parts are hard to source – Rare Spares carries some new items, such as washer pump parts – so scour the internet, wrecking yards and the shelves at older auto electricians.

Let’s take a look at what can be done to get your old wiper motor working and looking like new.

STEP-BY-STEP

1. Before removing and disassembling your wiper motor, grab a digital camera and take plenty of pics for future reference. Arming yourself with a workshop manual or a spare ‘control’ motor isn’t a bad idea either.

Remove the through-bolts and motor housing first, then the armature. Be aware that the brush springs will want to fly free as you slide the armature out.

2. If your wiper looks like this, get another one; it’s likely you’ll need to buy several to get enough good parts to build a decent unit. Be wary of removed or exposed wiper motors as once they get excessively wet, they’re history.

The darker armature indicates a burnt-out motor — the smell should be a dead giveaway. Armatures can be repaired (rewound) but this can be prohibitively expensive.

3. If you’re chroming or zinc-plating the armature housing, remove the magnets. Mark their positions as they must be re-installed in precisely the same orientation. Normally there are fine white paint dabs, which go to the top.

Use a couple of small screwdrivers to hold out the retaining clips and a couple of gentle taps with a slide hammer will pop them out. Be careful — they’re brittle.

4. The crank-arm is on a tapered shaft; after removing the nut, use a prying action with a screwdriver or puller to remove it. The driven wheel (big round thing) should slide straight out.

Unfortunately the sintered bush had seized onto the shaft on this unit so it had to be hammered out (note nut on shaft). The housing was okay, so it was freed up, lubricated and reinstalled.

5. Wow, what a difference! For ultimate show, chroming is an option — just watch the small parts. However, the cheaper zinc-plating option will give you a more factory look and still makes for a finished job that you can be proud of.

The low cost of zinc means you can get extra parts plated (get a heap of parts done simultaneously) and choose the best-looking bits upon re-assembly.

6. The main body has various electrical components that are not easily removed, so leave them alone and give it a good wash to remove the built-up crud and grease.

For that fresh-from-the-factory look, mask off the vulnerable parts or areas and treat the body to a quick media-blast. Rewash and blow it out afterwards to ensure there’s no grit or other foreign material left behind.

7. The copper on the commutator is very thin and unless it’s heavily grooved it generally shouldn’t be machined. Clean it up with a bit of emery and then clean the grooves out with a knife or thin blade.

Don’t be too aggressive here or you’ll swage up the edges, which is not good. Inspect the winding for discolouration; if it’s black, it’s burnt out and will need replacing.

8. If the ends of the three contacts are badly worn, use a different body as they’re extremely difficult to replace. Smear grease on the underside of the gear wheel, drop it in, spin it a turn or two, then yank it out and check the contacts are rubbing in the correct spot (inset) — bend to correct. Oil the two bushes (see Step No.14) and liberally grease the gear upon final assembly.

9. Full brush-length is about 12mm — replace them if they’re down to 6–7mm; they’re readily available from your local auto electrician. Give the pigtails on the brushes a twist to hold them back, allowing you to drop the armature back into place.

Note that the crank arm is only bolted on finger-tight for the time being, to help keep the driven gear in place while assembling.

10. To spin, the armature requires a certain amount of end float. This small cone-shaped sintered-metal bearing — and a ball-bearing in other end of the armature — accommodate end float and manage any thrust loads.

During reassembly apply plenty of grease to the worm drive, and some to either end to hold the cone and the ball-bearing in place and ensure they’re well lubricated.

11. With the armature in place, untwist the pigtails and let them snap out against the commutator — give them a flick to ensure they move freely.

Although you should have checked to see if there’s excessive play in the bushes a few steps earlier, it won’t hurt to give the gearwheel a wiggle to check how much pay there is. If the bushes are overly sloppy, replace them.

12. Be sure to wipe up any excess oil from lubricating the bushes. When installing the motor housing, note the detent in the housing and the matching cut-out in the gear housing.

They should fit neatly together by hand — do not use the screws to force them together. This is a tricky operation as the motor magnets will want to grab the armature, so get a good hold.

13. If you opt for an external electric washer system, there’s no need to install the factory set-up, which leaves the washer driveshaft protruding.

Preslite made the same wiper motor without a pump; some had smooth covers, while others used a small plastic sealing cup over the protruding driveshaft. Scour the wreckers for either of these examples, or make your own cover.

14. All that’s left is to fit the washer pump assembly. Running out of lubrication kills electric motors, so lube all the porous sintered-bronze bushes during assembly.

Do so by plugging one end with your finger, filling the bush with oil, then squeezing both ends between your fingers. This forces the oil into the pores of the metal, where it will stay and lubricate for another 15 years.

WASHER SYSTEM

The original automatic washer system simply mounts on top of the wiper motor and uses an actuator-driven diaphragm, a lot like a mechanical fuel pump. Time and engine bay heat leave the old plastic parts brittle and often broken. Some new washer diaphragm bits and occasionally NOS gear sets are available — try Rare Spares.

Otherwise if you want originals, scour wrecking yards and the internet for secondhand stuff but be aware that original parts in good nick are rare. If any of the little valves or springs are shot, it won’t work; you’ll probably have to salvage parts from numerous units to make one good one.

Alternatively, delete the factory washer section altogether and replace it with a universal-fit aftermarket washer-bottle with built-in electric pump. Ford (vertical) and Holden (horizontal) styles can be had for little money; Rare Spares offers reproduction bottles without built-in pumps.

Outlet nozzles can be bought new but if using originals, clean them out with an oxy tip cleaner and compressed air, being sure to blow inwards rather than outwards.

WRAP UP

It’s a good idea to bench-test it first. To do this, use a 12-volt power source (car battery) and make sure that you make all the same connections to the unit as in your car’s wiring diagram or you may damage the motor. If it performs on test, go and bolt it on! Vibrations will kill the motor so be sure to re-install the vibration-absorbing rubber washers and bushes when refitting the assembly in place. And don’t forget the copper earth-strap, as the motor will not work without it due to those insulating rubber mounts.

Also make absolutely sure that neither the earth-strap nor any wiring can foul on the wiper crank arm. If it’s sluggish in operation, check the voltage and be sure it’s earthed properly. Always fit new blades and don’t neglect the rest of the wiper system, such as the pivots and the arms that operate them. Remember the wiper motor will only be as good as the system that it’s driving!