Aarrgghh, not the Bl***y Alarm Again?

A couple of days after we got home from Brecon last month, the Autowatch 695 alarm on our motorhome, SOK, started going off every few hours for no discernible reason. This post documents what happened and what we’ve learned so far, just in case we have to revisit the issue at some point.

Background

SOK is a Benimar Tessoro 481 motorhome. The base vehicle is a Mk8 Ford Transit.

We had the Autowatch 695 alarm fitted not long after we bought SOK in late 2017. We’d had a tracker fitted by Ceirtech in Gaerwen, Anglesey, the day after we picked the van up from the dealer (that’s another story) and were so happy with the service we received that we booked SOK back in to have an alarm fitted too.

We’ve had no trouble at all with the alarm until now.

Lots of motorhomes seem to be fitted with this model of alarm but we hadn’t heard of anyone having any particular problems, so our first point of call was the trusty old internet to do a bit of research on the alarm and what might be setting it off.

Autowatch 695 Alarm

The Autowatch 695 alarm is a Thatcham-approved CAT 2-1 upgrade alarm system “designed to be used on full CAN Bus, semi CAN Bus or conventional wiring systems” according to the manufacturer.

CAN Bus – is that some kind of Public Transport Initiative?

It turns out that CAN is short for “Controller Area Network” and CAN Bus basically refers to the clever electronic gubbins that allows various vehicle components to talk to each other, for example to tell a light on the dashboard to illuminate if a bulb goes. Our alarm links into this system so that, for example, it gets set automatically when you lock the vehicle using the standard Ford central locking fob.

I say “basically” as if I knew any more than that. Don’t be misled – I don’t. I’ve decided to just think of CAN Bus as some kind of wizardry that allows things to send messages to each other. Hopefully I’ll never need to know any more than that.

The internet did give us a few suggestions as to things that might be setting the alarm off:

Ultrasonic Sensors or PIR Sensor

We have ultrasonic sensors in the cab and a PIR sensor mounted on the wall in the habitation part of the van. Could it be that something was triggering a sensor? In that case, there would be nothing wrong with the alarm; it was just reacting to something actually happening in the van.

Ultrasonic sensors work by sending out sound waves (at a high frequency that humans can’t hear) then turning the reflected sound into an electrical signal which, if it meets certain parameters, will set off the alarm. It seems that movement in the van can do this (as you’d expect) or that air movement might even be enough.

The first night the alarm started going off was extremely windy, so the ultrasonic sensors did seem a possibility, although it had never happened before in the time we’ve owned the van. We checked carefully for any critters (flying or otherwise) that may have stowed away in there: none found. I moved anything I could find hanging up in the van that might sway if the van rocked in the wind, Mark’s cookery apron being the prime suspect on that count. Finally, I closed all the air vents in the cab, as suggested in one blog post I found online.

None of this worked – the alarm kept going off every few hours.

The PIR sensor didn’t seem to be as strong a suspect. It works by detecting changes in the infrared energy hitting the sensor, so my understanding is that you need something heat-emitting (ie most likely alive) to trigger it. We’d already checked for critters and the van wasn’t on fire, so we left the PIR sensor for the moment and moved on to the next suggestion we’d found online.

Bonnet Sensor

It seems that normally, this alarm includes a bonnet sensor so that the alarm will go off if the bonnet is opened. The sensor is a little plunger-type thing. When the bonnet is closed, it mechanically presses the plunger down; conversely, if you open the bonnet, the plunger pops up. The alarm therefore knows whether the bonnet is open or closed at any time.

From what we’ve read online, the bonnet sensor is often installed against compressible material (eg soundproofing) attached to the underside of the bonnet; as this gets squashed over time, the plunger doesn’t get pressed down fully when the bonnet is closed, and eventually, the alarm can start to think that the bonnet is open when it isn’t.

This all sounded highly plausible, but when we checked we couldn’t find an Autowatch bonnet sensor. All we’ve got is a very sturdy-looking Ford one which closes against bare metal (we later discovered that we don’t need a separate bonnet sensor as the CAM Bus thingie already knows if the bonnet is open or not).

Onward and upward. It’s all one big learning experience!

Batteries

The PIR sensor inside the van and the sensors we have fitted to all of the locker doors are battery-operated. We’d never changed the batteries, and a failing sensor battery can apparently upset the alarm. So I trotted round with a stack of new CR2025 batteries and changed them all. Once again, we were hopeful.

Nah. In the middle of the night, the alarm started going off again….

The only other battery mentioned online was the van’s starter battery. Apparently, if the starter battery goes flat, the alarm can decide that its power supply has been cut, which would trigger the alarm.

We HAD experienced a strange flat battery episode a few weeks earlier, which we’d put down to a cab reading light being accidentally switched on. The switch is extremely easy to knock with your head as you move between the cab and the habitation area, and the lights are such poxy little LED things that it’s easy not to notice.

This had happened before we went to Brecon, though. Mark recharged the battery before our trip (which thankfully seems unharmed by this little mishap) and on our return, its voltage still looked good, so it seemed unlikely that this was what was troubling the alarm. Also, you’d imagine that this would set the alarm off straight away rather than intermittently every few hours?

Time to Call in the Cavalry

We’d now exhausted the list of tips we’d found online. It was time to call Ceirtech. As we only had a couple of days before our next trip, we booked SOK in for a couple of days after we got home.

On our recent trip to Yorkshire, we circumvented the problem by not using the alarm; we locked the cab doors from the inside then exited via the habitation doors in the same way that we do on ferries when we don’t want the alarm turned on.

On returning home, we set the alarm again. We’d read that the memory on the alarm diagnostics would reset: either

1. according to information we’d found online, after ten cycles of the ignition being turned on and off, or

2. according to the alarm installation instructions, after ten times of the alarm being turned on and off again without triggering.

It’s unclear which is correct but my money’s on the installation instructions. Either way, our trip to Yorkshire might have cleared all trace of the problem. We figured if we left the alarm turned on when we got home, it would go off and we’d definitely have some diagnostic codes in there for the next day when we took it to be looked at.

Erm, no. The cursed thing didn’t go off. We took SOK to Ceirtech the next morning and left him there all day – the alarm didn’t go off then either and there are no diagnostic codes in the memory from before our trip to Yorkshire. It’s always the way that things stop playing up when you take them to be fixed!

Really great service as usual – battery voltages etc all checked and a call to the manufacturer for their thoughts. We didn’t even get a bill: “all I’ve done is piddled around with it for a bit”. I’d have thought it was completely reasonable to charge an appropriate amount for piddling around, but apparently not….

Wot no Diagnosis?

No-one really knows why our alarm started going off every few hours a couple of days after we got back from Brecon, but is suddenly behaving again now we’re back from Yorkshire.

One possibility we were given was that something was going on with the alarm back-up battery (which is what allows it to set the siren off even if a wrong-un cuts the power feed to the alarm). It could have somehow got depleted, then a good run has sorted it out?

I guess the alarm backup battery could have been depleted by the long months on the drive during lockdown or when the engine battery was flat a few weeks ago, but surely the trip to Brecon we’d done (returning home a couple of days before the alarm started playing up) should have sorted it in that case?

We don’t know enough about how the alarm normally draws power (from which battery, when?) or how the backup battery recharges (is it only when the engine is running?) to be able to come up with a plausible hypothesis about what might have happened.

All we could do now was wait and see what happened. If it went off again, hopefully we’d get some diagnostics in the alarm memory to point us towards the cause.

The Current State of Play

A week later and we haven’t heard a peep out of the thing.

It’s a bit of a pain really as I’ve been sat here with my running shoes on ready to leap into action and dash outside at the first wail of trouble – we’ve been given the task of checking whether or not the indicators flash when the alarm goes off.

That does sound completely ridiculous, but apparently, not flashing the indicators would be the alarm’s way of informing us of an actual problem with the back-up battery unit (rather than a sensor or something else triggering the alarm).

Not flashing the indicators? Really? I thought this flippin’ CAN Bus stuff was supposed to be a master of communication? Why can’t it just send us an email in plain english, for God’s sake?