Whacko Tacho - Blackbourn 446

By: Rob Blackbourn

Date: 06.12.2020

Rob reckons having a rev-counter in a knockabout ute comes under the heading of 'too much information'

It was just after I heard the radio-news item about Coles supermarkets shutting down due to a nationwide IT failure that the tachometer needle in my Hilux sagged to zero.

No, I hadn’t arrived home and switched off the motor – I had just come off the freeway and was backing off the throttle for the run down to the roundabout. So the faithful old diesel-four was still punching out plenty of rpms; but those rpms were no longer being counted.

Although the old ute still runs like a bought one, I’ve been having fun and games with the tacho as well as the coolant-temp gauge for a few months. The thing is I’ve generally been able to coax the tacho back into life with a swift slap to the top of the dash (had to apologise to the co-pilot for startling her the first time I did it without warning).

Toys to tracks? - go HiLux

Unfortunately while slapping the dash can be effective in waking up the tacho, it can cause the temp-gauge needle to lie down. But a lateral whack on the left of the instrument fascia usually revives the temp-gauge. However the fascia slap that fixes the temp-gauge is inclined to shut down the tacho…

Not a man to turn and run from a challenge, I’ve developed a suite of nuanced slaps (why should ‘suite’ and ‘nuanced’ be confined to press-releases and marketing-blurbs?), with the force and direction adjusted according to what’s up and what’s not at the time. It was going fairly well actually, no doubt allowing any skilled lip-readers in oncoming vehicles to ‘hear’ my triumphant ‘Y-E-E-S-S-S’ when the two troublesome needles finally sat up and paid attention. Together!

This time though, despite my best efforts over the last few kays to home, the tacho needle remained unresponsive. It had found its final resting place.

Why did I stick with happy-slapping instead of sorting the problem properly? Well here’s the thing: Yes, I did turn to the tools when the tacho first misbehaved, only to discover that the instruments are mounted on a printed-circuit board. Now that was a setback – who knew an ’86 Hilux, a basic, old-school, low-tech, knockabout ute would be hiding a printed-circuit board behind its aging clocks? The issue there is that printed-circuits don’t age that well and defects are so difficult to locate and repair properly as to make them virtually unrepairable.

Decades ago diodes were the first of the electronic non-repairables to challenge my happiness, when I discovered half way up the Newell Highway that a failed alternator couldn’t be resuscitated like an ailing generator using traditional techniques and basic items like emery paper, copper wire, pliers and screwdrivers. More recently, as well as diodes you’ve got printed-circuit boards, epoxy-sealed modules and multiple ECUs with their client-sensor networks – remember crank-angle sensors in 1990s Commodores? How good were they?

I know many of you are feeling versions of my pain. Letters from readers Aussie and Gary in the last issue of Unique Cars, two mature gents like myself, registered their automotive technology concerns. Young Guido, the esteemed Ed, has also put in his two bob’s worth on the subject. I should acknowledge though that rather than repairability issues, their beefs are with higher-order tech-systems, of an insidious kind that fights the driver for control of the vehicle. Given that my ownership ambitions generally focus on pre-1980s classics, these are aggravations that I’m likely to be spared.

You might be surprised to learn that I have no plans to revive the tacho. The fact that a diesel Hilux, particularly one featuring an auto trans, had a tacho at all struck me as odd when I bought it years ago. She plugs along between 1500 and 2500rpm most of the time, reaching the giddy heights of 3100rpm at 110km/h on the highway. So redlines and the like are concepts quite foreign to my Hilux experience.

Lest you fear I’m being cavalier about the other dud item, the temp-gauge, I’m happy to say that I regard coolant temperature as something worth monitoring, even in an old Hilux. I’m in the course of fitting a mechanical temperature gauge that, bless it, bypasses troublesome electronics altogether. As many of you know it uses ether-vapour expansion in a flexible metal capillary-tube running between the thermostat housing and the gauge to move the needle. Happy motoring…

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