Sigma M30 alarm immobiliser indicator stuck on

[chevrons2]

Hi. I have seen this problem on a few forums but haven't actually seen a definite fix. Having now fixed mine, I thought I would share what I did.

Fault:

I have a UK spec 2003 Forester SG (non-turbo). Occasionally, when using the remote to lock or unlock the car, although the right-hand indicator would flash a few times and then go off as normal, the left-hand one would just stay on. At first, when this happened, I would just press the remote a few times until it sorted itself out. As it started to happen more often, it became more and more difficult to get the left-hand indicator to turn off. I looked on various forums and it seemed likely that the fault was due to a sticking relay within the Sigma control unit. Some people said that the unit was around the steering column area, above the pedals. Other people said that it was behind/above the glove-box. On my 2003 right-hand drive Forester, it is above the glove-box, housed in a gold-coloured metal box.

I removed the glove-box and left it out until the next time the fault occurred and sure enough, tapping the metal box lightly immediately made the stuck indicator turn off. I removed the metal box and opened it up to reveal the black plastic Sigma unit inside. The cover on the plastic Sigma box is held on with small posi-drive screws. I disconnected the Battery at this point but found that it was not strictly necessary, as long as I was careful not to let anything touch the exposed circuitry inside. You can decide for yourself whether you want to take that chance, (but I would not advise disconnecting or reconnecting the Sigma unit wiring while the Battery is connected).  I removed the cover, to find 3 square relays and one rectangular relay on the printed circuit board. I left it dangling (away from anything that might short anything out) until the fault re-occurred, so that I could try to determine which relay was sticking, by tapping it. The slightest tap on any of the relays would unstick the stuck indicator, so I had to test it with a meter. This is what I found:

Identifying the faulty relay and trying to source a replacement:

The 3 square relays are mounted in an L shape. The two closest to the edge of the PCB are each for a separate immobiliser circuit. The square relay mounted nearest to the long rectangular (central locking) relay, is the one that operates the indicators. The 3 square relays are identical, all having the same markings and numbers: "OEG OARW-  SS-112DM  12VDC  08082 C". I don't know what any of that means, so I asked a local company that produces PCBs and electronic stuff. they couldn't find an equivalent but told me that "OEG" was the manufacturer and that they had been taken over by "TE", an American company. I contacted them with the details and pin dimensions etc. They were useless and offered me the "closest match" which was nothing like the original. I contacted RS-Online, who were honest enough to say that they didn't have anything like it. I contacted Farnell, who put me through to the technical dept and I was given the part number of the only one that was similar, having exactly the same internals and pin lay-out but the pins were slightly further apart. I bought one, thinking that I could mount it remotely from the PCB. luckily, when it arrived, I tested it's operation before fitting it: It was NOT the same internally.

A "normal" 5-pin relay, (like the wrong one that Farnell supplied), has a +ve and a -ve connection that operates a coil. when activated, this coil acts as a magnet, that pulls a metal strip away from one contact, (breaking a circuit), and towards another contact, (completing a circuit).  The 3 square relays in the Sigma unit don't operate this way. The coil part is the same but when it is activated, it connects 2 circuits at the same time: It connects a common feed to two separate circuits. In the case of the relay used for the indicators, it connects a live feed to the left hand indicators via one pin and the right-hand indicators via another pin, at the same time. Once I discovered this, I realised why someone on a forum somewhere had said that replacement relays were not readily available.

My Solution:

While checking the various relays and connectors with a meter, I discovered that the square relay nearest the corner of the PCB was not being used. This was confirmed by the fact that there was no wiring to terminals 13 and 14 in the block-connector. Some of the soldered connections are very close to other circuits on the PCB so I employed a local TV repairer who was experienced in working with PCBs: I paid him £10 to remove the faulty indicator relay, then remove the unused relay and solder that in to the place of the indicator relay. I put it back on the car, crossed my fingers and connected everything up: Perfect. Cured. Everything now works as it should (and has done for 3 weeks now).

The Sigma M30 is used on various cars, not just Subarus. I assume that on some cars, all the relays are used but it seems that on Subarus, (or at least on mine), as no wiring was fitted to the block connector for that circuit, the associated relay just sits there unused. It's nice of them to supply a spare!

If anyone else has this fault and is thinking of doing what I did to cure it, you obviously need to check whether or not that relay is being used. The main connector block has 20 terminals. Holding the PCB with the relays pointing downwards, (hanging under the PCB), and looking into the block-connector from the cable side, terminal number "1" is at the top left. The top row goes from left to right, "1" to "10". the bottom row goes from left to right, "11" to "20".  On my car, terminals "3", "4", "13", "14", "18" and "19" had no wires in them. "13" and "14" are for that relay.

Other options(?):

If you find that you don't have a "spare" relay in your Sigma unit, then I suggest you have 3 options.

1): Buy a new complete unit, (if they are still available).

2): Find a suitable replacement relay (but make absolutely sure that it IS suitable!). I couldn't even find one with the same pin spacing, let alone the same internal circuitry.

3): (This option is not my suggestion. It is what I have seen suggested on a forum somewhere. I did not try this option. I don't know whether it will work or cause other problems. You must decide for yourself). Cut the two indicator output wires a little way from the unit. Insulate the output wire that relates to whichever side indicator is sticking on ("16"=left. "17"=right). Join the one 'good' indicator output wire to the two cut off wires that go into the loom BUT you must do this via two diodes to stop back-feeding from one side indicator to the other, unless you want hazard flashers every time you indicate!

Please be aware that, as this is a Thatcham approved alarm, changing it in any way may affect your insurance.

(As this is my first post here, any feedback would be appreciated).

 

Edited March 1, 2016 by chevrons2
Removed some info that may have been useful to car thieves!

[Mr B]

Good post & info ...

another option is you can wire off board two normal single circuit relays to do the job of the one double circuit, using the spare is easy way go & glad your effort paid off. great first post .

[Emrys]

This is a late pick up - but same problem with the M30 box here. 

 

Do you know if the M30 box is a generic one, or tied to a specific car / alarm / immobiliser? Unfortunately I dont have access to electronics capability. I've seen a few on eBay for £30 and wondering if I can just switch it out? 

 

Thanks so much

[Mr B]

Yes any M30 will do BUT be sure have one working remote or pin code supplied with used unit or it useless unless got sigma software program it .

With one working fob you be able program your key fobs and set the 4 pin code

any decent breaker always sells them with a fob, expect pay more than £30 for workable option .