MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - SRS Problems - Help please!

I'd really appreciate some help on this. Problem is as follows:
Red Warning SRS light comes on intermittently - It is usually on about 60% on the time I'm driving. (This has been happening for the last three months or so.

There seems to be absoltely no pattern as to whether it 'decides' to be on or off. It stays on or off for extended periods (hours or days) - i.e. it doesn't flicker.

I've taken the seats out, checked the connections - No improvement.

I've taken the car to B&G who put it on the test machine and "sorted" it out - checked the wiring behing the driver air bag - put it together again - gave it back to me - no red light showing - Sucess!!
- until the next day when it came on again. I've been back to B&G and asked their advice as towhat to do - the response - a metaphorical shrug of the shoulders. I'm understandably hesitant to pay to have it put on the machine again wihout any sort of security that this will be a never ending process of *not finding* the fault at 50 quid a time.

However when driving on the motorway at the 70mph MGF owners always maintain :-) It is HIGHLY disconcerting to have this bright red light in your face - The thought of the airbag suddenly going off without warning whilst your doing xxxmph in heavy motorway traffic is distinctly unnerving. (Imagine the situation and you'll know how I feel!)

I have been told by the B&G mechanic that if the red light is showing the SRS is disabled and therefore safe. However this opinion wasn't positively reinforced by the workshop manager.

Can one or some of the experts point me in the right direction as to what to do. I'd rather disable the whole system than have the current scenario but this doesn't seem to be that easy to do - What happens if you remoce the SRS fuse that clearly states "DO NOT REMOVE"

Apologies for the long post.
Thanks in anticipation,
Mike M60 BOY
Michael Boy

SRS light on means that the system is disabled so the air bag(s) and seat belt pretensioners are now dissabled.

Diagnostic function checks are carried out continuously by the main control unit that is under the trim in front of the gear lever. However locating internal system faulst requires Testbook.

If the times when Testbook is connected no fault is detected then your options are limited to a physical check of all cables connections and components for physical damage, or for a systematic change of all components until the fault condition is lost. Not a very pleasing prospect!

I would expect the problem to be one of a failing connection, in perhaps the rotary coupling on the steering column, or a problem where the wiring for the pretensioners is under the seat. Logic says that where there is any mechanical movement then this is the likely spot for actual wiring failures. Another check should be done to any earth points, for example the wire earth from the main control module to the body which is alongside this unit.

Since the problem arose, was there any recent work inside the car as this could be connected to triggering the problem. Many problems have a sequence of events that with a little thought can be laid in place and then a target area is defined to check parts.

Rog

Roger Parker

reading all this and recalling former failure reports of the last three (they were only a few precise here). I would assume an intermittent failure at the rotary coupler.

Only a thought !!
Some pictures to show the items are here
http://www.mgf-net.de/srs_system/index.htm

Regards
Dieter
Dieter Koennecke

Alright Michael,firstly as Roger correctly states when the light is on the system is safe and disabled.
secondly your fault sounds like 1 of 2 possible problems(with out testbook plugged in cannot be 100% sure),
1. there have been a few cases that the gases omitted
by the seat base sponge start to slightly corroid the terminals under the seat so you will need to disconnect ,clean them and spray them with a non conductive protector spray,sounds far feched but true.
2. 9 out of 10 times the fault tends to be the rotory coupling,which is the srs part directly behind the air bag itself.
as i say with out test book plugged cannot be 100%sure
so i hope this helps.
Dave
Dave mgf tech

Hi Mike

I had the same problem some time a go I Disconnected
The battery and charged it for 24hrs then reconnected It.

It worked for me.....

Then a year later i got a new one from halfords...
My MGF is 4 1/2 years old.

Natasha.......
Natasha

I suppose that Testbook hasn't got any useful 'RESET' function included.

The MEMS has, but obviously the SRS ECU and also the Alarm ECU hasn't.
If so, than this term on reset by discharging the ECU (disconnecting the power for some hours) should be included to all FAQ sites.

Can someone confirm ?

Mark the techy ??

Regards
Dieter
Dieter Koennecke

Thanks all,
Your comments and opinions much appreciated. Sadly it would appear that there is no clear cut solution to the problem. :-(

It's a pity one can't isolate the various sections of the SRS and establish the area of the problem.

I'd still lke to know what happens when you take out the fuse which is clearly marked "Do not remove"

I am relieved to be assured that when the light is on, the system is disarmed and is safe - I suppose it's just going to be a tedious process to find the fault.
Michael Boy

My SRS light still comes on but only on a particularly hot day (EG recently). Once the hood is down and a little air has circulated, I turn off the engine and on again and ..... no SRS light on. Until the next time the car is left out in hot weather again.

Never a problem in winter so I assume that something about the electronics is heat sensitive.
andrew northcott

I'm trying the easiest option tonight - battery disconnected. We'll see tomorrow. Sounds like I'm not the only one who's had this kind of problem though.

I dread the thought of trawling through the entire SRS system trying to isolate the problem.

Anyway - keep you posted.

Mike M60 BOY
Michael Boy

OK That didn't work - Next steps?
Michael Boy


Hi all,

The presence of the SRS light does not indicate that the whole system is dis-armed - It merely indicates that there is a fault in the system, and the other parts (ie; the non faulty parts) of the system will continue to function as normal.

Testbook will give codes that indicate which part of the system is causing the SRS light to come on.


Gerald
Gerald

Oh yes... the yellow capped fuse.

If you pull this fuse out, it cuts the power feed to the SRS DCU - thereby disabling the total system.

BUT

You will have invalidated your insurance..... !

Gerald
Gerald

OK so we now have some debate as to whether the whole system is disabled when the light is on.!!!

One definite effect of disconnecting the battery overnight has now become obvious - the light now stays on ALL the time (three days now) This may actually help though - the last time I took it B&G the light was off so there wasn't much point in putting it on the test equipment again!

Surely a fused fuse in the fuse socket would not invalidate the insurance - not that I'm intimating anything ;-)

Mike
Michael Boy

Have also had SRS light on intermittently, usually it has been hot weather so I have been wondering if there is a heat sensitivity. It goes off when I re-start the car - but is happening nore frequently. I had problems with the heater control (couln't lower temperature) which is now fixed, so I though t it was connected to this..
Simon

My SRS light is permanently on....I am going to book it into a garage as hopefully this will be covered by my warranty company. I will let you know what they say the fault was when I have it back. Wont be until a week or 2 tho'.

HTH

Mike
Mike

Mike in Swansea - good luck. At least yours is on all the time. Mine has reverted to being intermittent. the day I planned to take it back to be put on the test machine it was off all the time. Came on the next day though. :-(

Mike
Michael Boy

I went through this before.

You have to replace the rotary coupler. [inside the
steering wheel]

I haven't read through the thread completely, but

this will solve your problem.

For me Rover paid 30% of it.

Regards,
Hanah
Hanah Kim

Is it true that reading about MGF gremlins on this BBS makes them attach themselves to your car? If so I am going to stop reading about HGF!

On the way home from a weekend away, we stopped for lunch. After restarting the car the SRS lamp stayed on permanently. Got the car home, opened and remade the connections under the seats. Lamp still on. Reversed car into garage, switched off, read the BBS again. Restarted the engine - light goes off

I don't think I have heard the last of this?
brianh

Hi all,

watching this thread develop with interest as my girlfriends 97VVV has just started this SRS problem.

One day you go out light comes on, stays on for 1-2mins goes out. Next time doesn't come at all, next time stays on for the whole journey!

I think the suggestion's about the rotary coupler make the most sense, ie a part subject to wear etc. My tack with MGR is going to be (subject to this thread); the user booklet says that the airbag system needs replacing after 10 years (inside cover somewhere in the owners guide) on that basis by inference the system is expected to last at least this long, so warranty or not, down to MGR I say to fix.

Haven't tried yet, but will give the hotline number a go this week....

Neil
Neil

I'd obviously be very interested in their response. What sort of costs are involved in replacing the coupler?

Mike
Michael Boy

Get a print out of the Test Book results! On this side of the pond,[ on L-R veh.] we have seen seat belt retractor problem codes. Change the seat belt buckle end , done . This may 0r may not be your problem,battery low voltage problems were a concern on earlier LRNA veh.'s. In which case repair the charging system / clear codes & go! Get the print out!! Len
Len Fanelli

I'm sorry to tell all you people who think that the SRS system is still operational when the light is on ,you are all very much mistaken as the light is there to let you knoe that the system is shut down and will not be activated if a crash was to happen so you need to get it sorted as soon as possible.
If the system was still active when the light was on ,well who know's what will happen,so it's NOT active when the lihgt is ON.
Dave
dave mgf tech

NOW Dave has told all you ignorant so and sos what it is all about - funny though didn't Roger tell us that in the second posting of the thread.

AND I am sure the handbook says the same!

Ted
Ted Newman

Why thank you Ted for underlining my statement and yes you are correct it was mentioned in the second thread by young man named Roger but if you care to look a little further another man named Gerald disagrees causing a small amount of confusion.And from my experience not many people tend to read the manual,but i can see that is not the case here.
Dave
dave mgf tech


OK guys - this is going to cause a certain amount of stink here!

Please understand, Safety Systems are Life Critical - so they are dangerous.

When the SRS light is illuminated, it does not automatically mean that the whole SRS system is disabled. As I have said before, it merely indicates that there may be a fault in the system.

On the other hand, there are certain conditions when the lamp is illuminated, and no firing activity will take place in the event of a crash that warrants it.

Under "normal" conditions, lets say that the connector has fallen out of the passenger airbag squib. The SRS lamp will illuminate, and subsequently, in the event of a crash that warrants deployment, and subject to certain other factors (the condition of the fault of the system, short cct, open cct, 12V etc.), the remaining circuits will attempt to fire. So in some cases, the driver bag, and pretensioners will fire.

There are some cases when the SRS lamp means that nothing will happen: eg; crash-locked DCU.

If in doubt, the back-desk should be able to clarify.

I am speaking as a private individual, as my contract of employment (past & present) precludes me from speaking from a position of authority!


<puts on tin hat and waits>
Gerald

An interesting debate!

I take it from Geralds remarks that he is (or was) involved in some way with the SRS systems in our cars and therefore is telling us something that is contrary to what is said in the official manuals.

So MGR (Rover) tell us that when the light is on the system is disabled - I take it that this is to cover their 'butts' in the case of an accident and not as a safe-to-work-with feature.

HOWEVER which ever statement is true is immaterial as surely what the 'Light On' means is your full SRS is not working correctly SO get it it fixed!

Ted
Ted Newman

More information:

From the owners manual (RCL 0332ENG) 2000:

"The warning light mounted in the instrument panel will alert you to any malfunction of the airbag SRS"

and in a different section of the manual:

"The light illuminates when the starter switch is turned on and extinguishes within approximately six seconds. If the light fails to illuminate or illuminates once the engine is started, the system is faulty - seek qualified assistance urgently"

I couldn't find any reference to the system being disabled if the light was on..... (maybe I hadn't looked hard enough).

I don't *think* that I am at odds or contradicting MG-R. - if someone can find reference otherwise - lets hear it on here!

As to the yellow-capped 5A fuse - If this fuse was removed (or blown), then the SRS lamp would illuminate - telling you there was a fault in the system.

With the fuse removed, this is the occasion with the highest probablility that the SRS will be disabled (although there is a reserve energy system that will still fire the circuits, eg; in the event of an accident, the battery becomes disconnected, but the circuits will still fire if required). This is why there is the appropriate "waiting time" for the energy reserve to deplete if you disconnect the fuse to work on the seats, sterring wheel etc.

Above all else, there is a set proceedure for working on these systems - follow them!

As for my involvement - I can't comment either way, so would appreciate others from speculating, as this could get me into trouble, and lead others into perhaps false senses of security that the information provided here was *absolute*!

<puts on a second tin hat>


Gerald

Gerald sounds eminently plausible and sensible to me. I've booked my car into B&G on Saturday again. The light is on continuously now which should make diagnosis easier. Hopefully they can identify the fault. Be interesting to see if they charge me, having paid 50 quid for them to not fix it last time round.
Mike
Michael Boy

As per my previous post "the light is on continously now" and I've booked the car into B&G this morning" - except that driving home last night the light went off and stayed off!!! I can't see any point in putting the SRS system on the test if (according to the light) it's working correctly. I think there's a sensor somewhere that knows when I've booked the car in and then extinguishes the light simply to frustrate me. It's been on constantly for the last three weeks prior to last night.

Grrrrrrrrrrrrr.


Mike
Michael Boy


The DCU stores the fault codes - so they should be able to recall them using testbook!

It isn't rocket science (I wonder what phrase Rocket Scientists use!!).

As mentioned previously, the most common intermittent faults are usually the connector under the seats for the pre-tensioners, and failure of the rotary coupler.

Hope you get diagnosed soon!

Gerald
Gerald

Thanks Gerald,
Sorted now it seems. B&G replaced the rotary coupler on Saturday and I haven't had a problem since.
£232 for the consultation though. At least it's fixed.
Thanks to all for the comments and advice.
Mike
Michael Boy

232 quid, Oyyyyhhhhh !!! :(
How much was the parts price ?

Guess I should wrap my spare coupler in cellulose wadding
;)
http://www.mgf-net.de/rotary_coupler/indicator_4305.jpg

Dieter Koennecke

£72.33 + Vat less £10 discount. The rest was labour. In all fairness to B&G the fault was intermittent and I certainly don't feel badly done by as they certainly spent the time charged working on the car.

It would have been far cheaper to simply replace the coupler. However, the luxury of hindsight is only available after the event.

Mike

Michael Boy

cheaper still to take the bulb out of the dash.
pinky

This is a problem I've heard about from several friends with different makes and models of car.

Several have had great problems with diagnosis and a "replace the most expensive bit and see if that cures it" approach from garages, or the "can't find anything wrong gov's so can't do much but I'll only charge you £50 for the priviledge of looking at you light in a technical manner" approach.

In all cases I've known of, 4 or 5, it has been either the steering wheel rotary coupling or the seat belt connector under the seat.

I would suggest a little self diagnosis,

1) Jack up the front wheels of the car (placing it on secure axle stands) start the engine and rotate the steering wheel from left to right reapeatedly and see if this has any effect.

2) Start the enging and holding the lever up slide back and forth in the drivers seat first, then the passengers seat and see if theis has any effect.

You may be able to narrow down the problem for later rectification by the garage without having to pay them for several hours mucking around.

Is the rotary coupling sealed, or can you get to the contact rings to give them a good clean? I've never done this with srs system, but it used to work well on the ford horn and cruise control contalcts!

I think it would not be too sensible to ignore any problems with the srs, but it would be foolish to try any diy electrical work on the system (probing around connectors disassembly etc.) unless you are certain of what you are doing. Never work on the system with it "live" and be very carful using any type of tester as they could provide enough power to activate the firing circuits!

While on about srs, I saw a fireman interviewed ages ago on TV who wanted all cars fited with a special point on the outside of all cars with srs systems so the fire brigade could safely fire all air bags etc before moving vehicles or dealing wiht them when on fire, a good idea? I just can imagine so little moron getting hold of the special device and firing all the air bags on the cars in a street on night just for kicks!
Andrew

>Is the rotary coupling sealed, or can you get to the contact rings to give them a good clean? I've never done this with srs system, but it used to work well on the ford horn and cruise control contalcts!

Please notice, this is no moving or sliding contact but only a long winded thin PC-board. A so called stripconnector with crimped contacts at both ends.

The crimp connections are the point of trouble. Strong crimp contacts to thin copper leads (only some mil thick and app 2mm wide).
Another problem is dismanteling the rotary coupler without knowing what someone does. The lenght of the winded strip is well calculated and adjusted due the number of turns of the steering wheel and should not be changed. So when you get off the steering wheel, than apply any adhesive tape to prevent the parts center and here in the stripconnector from unwanted turns !!

Some pictures are at
http://www.mgf-net.de/srs_system/index.htm
or another picture
http://www.mgf-net.de/rotary_coupler/case_termination.jpg
(will get a document at any time)

HTH
Dieter
Dieter Koennecke

I told u it's the rotary coupler!
:)

by the way mine was done free with only part price..
and i had 30% off..

you should have negotiated..
cuz it's a part that should not break down easily..
Hanah Kim

This thread was discussed between 02/09/2001 and 07/10/2001

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.