Gate Expectations

  • Gate Expectations
  • Gunge choked up the motor. Muck can be seen coating the receiver PCB.
  • A good brushing removed most of the debris, and spray-on contact cleaner took care of the rest.
  • A bit of angle grinding here, a bit of hammering and levelling there, and voila.
Date:31 March 2006

When the motor drive of your front entrance gate malfunctions, try de-bugging it…

THERE IS a very good reason for the existence of radio waves. They exist so that you can open your front gate from the comfort and security of your car, simply by pressing a remote control button.

Naturally, you can understand the consternation when one night I pressed the magic button…and nothing happened.

Having checked that the gate and its motor were still in place – thieves can be quite resourceful sometimes – and also that the power was switched on, I sensed the initial stages of credit card meltdown. This looked like a repair job at least. Possibly, even, a replacement.

Fortunately, for the time being I could get in and out. To allow for just such a situation, the drive pinion can be disengaged. After just a few seconds’ twirling it’s possible to slide the gate open and shut manually.

Once inside, just for luck, I flicked the remote button again. The motor whirred into life. So, with fingers crossed, I re-engaged the drive gear. We were back in business.

But, would you believe it, over the course of the next few days the glitch returned. Clearly it was that most irritating and puzzling of the species: the intermittent fault.

Elementary, my dear Watson
There were some clues, though. Such as, the gate motor worked fine during the day, but at a certain time of night it simply went dead.

Some basic troubleshooting logic eliminated a few likely offenders.

  • Gate obstructed? – No.
  • Motor connected to the electricity supply? – Yes.
  • Remote control battery OK? – Yes.

What drives my gate is a Centurion D3, typical of what you’ll find in domestic installations. It’s a 12 V DC motor energised by a maintenance-free sealed leadacid battery. Mains power does the recharging – although it can even be recharged by solar power.

An obvious advantage of this arrangement is continued operation during power outages. Centurion’s manual specifies 15 open/close cycles on a full charge of the 7 Ah battery, but maintenance technicians suggest that as many as 25 may be possible. Other plus points are high startup torque, precise motor control, and cool running. Domestic kits come with either the 220 V mains supply installed directly to the gate to power the charger unit and pillar lights (like ours) or a DIY-oriented split charger unit requiring only a low voltage installation to the gate.

Great, except that all our one did was sit there motionless. There was nothing for it but to call in a repairman.

Naturally, that didn’t stop curiosity getting the better of me.

Going undercover
My investigative tools were a combination of the manual and the manufacturer’s website (), which carries a helpful FAQ list and tech tips. (“Are the green IRB and LCK LEDs lit? When the gate is triggered, does the red TRG led light? Are any of the red diagnostic LEDs permanently on?”) I drew a blank. It was time to do a more detailed examination of the drive unit itself. Earlier, unclipping the motor cover had set off a scurry of ants. And there was worse. As I delved around the innards, around the base of the motor I noticed signs that a lizard-sized creature had been using it as – – a toilet.

It was then that I noticed that the receiver circuit board had been dislodged. Oh yes, remember a few weeks back when the gate refused to open? On that occasion, a helpful, technically minded visitor opened up the motor to see if there was something he could do. Until it was pointed out to him that there was a general blackout at the time and no amount of tinkering would restore the power. And it would work off the battery for a while, anyway.

At least when I moved the receiver and its rudimentary twin-core flex antenna back into position there was one positive change. Now, the relay could be heard energising with a click.

Still no action on the motor, though.

Idly, I turned over the circuit board and experienced another “aha” moment. Plastered over a couple of square centimetres of PC board track were the remains of what might once have been a slug. Or a gecko. Whatever, it was almost certainly bridging contacts and creating a short circuit. A few seconds’ scraping, brushing and wiping…and voila. Click…and the gate opened. Click…it closed.

Open and shut case
Which was more or less when the repairman arrived. Tempting as it may have been, I decided against telling him everything was in order. Despite the gate’s return to good health, it seemed like a good idea to have him inspect the motor anyway.

After a good look, he suggested a thorough overhaul to be safe. For good measure, he proposed relocating the motor to a higher position.

He confirmed my suspicions about the hazards of uninvited guests. “Ants…there’s your problem. With the motor being down on the ground you’re always going to have creatures crawling in there.” (How did I know he was going to say that?).

He also curled his lip while looking at the motor’s main circuit board. The board, and what he called its DOS (this is a computer?) could do with upgrades to the latest spec, he said.

One aspect that presented some difficulty was the arched design of our gate. It limited the options for repositioning the rack – as we would need to – when raising the motor.

Solution: turn the rack upside down, with the teeth on top. This means more careful cleaning and maintenance, but at least it did help provide a way out of our dilemma.

In the end, we settled on a job card that read:

  • Clean and overhaul motor unit
  • New operating system
  • Raise motor off ground
  • New lock unit for access hatch

Bolting a new support bracket in place raised the motor about 10 cm. Although the bracket is not readily available – it’s a purpose-made fitting fabricated for a specific company by a local metalworks – workable alternatives would include angle-iron stand-offs used as pillars to raise the motor. Competent handymen should be able to make a clone.

It was also necessary to relocate the magnetic trigger used for setting gate open/closed endpoints. Ordinarily this would be bolted to the top of the rack; in the new arrangement it is welded to a mild steel strap on the gate’s main horizontal crosspiece. A noticeable difference is that, because this new mounting flexes ever so slightly, it makes a loud clonk as it passes the motor’s sensor unit.

Finally, we decided we might as well do the job properly and replace the cam lock in the hatch that provides access to the release mechanism. The keys to the original had been lost, so we’d had to prise the hatch open to reach the knurled wheel that disengages the motor pinion to allow manual gate operation.

Besides, with the new lock, it represented one less point of entry for creepy crawlies. Even ones equipped with keys.

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