[Jimmy_MGF]

Hey all, I've got the MOT coming up so tried to the standard SRS fix (disconnect/reconnect both seat connectors a couple of times) but this time no luck.

Any suggestions on how I can diagnose where the problem is coming from, or some seasoned advice to point me in the right direction?

I'm also thinking of getting one of those USB OBD readers (my MGF is late 2001 so I think I can use this) - advice on a cost-effective one which you've successfully used would also be appreciated!

 

[mgbob]

A standard ODB reader is unlikely to help trace your SRS issue, they're fine for general ECU related items but they won't read SRS or ABS codes.

You're issue could be the rotary coupler on the steering wheel, these can fail on one or more circuits. If you're handy with a multimeter you can test these but it would be easiest to remove it to do this. If you do remove it, it's best to lock it in position to ensure it's replaced in the same orientation.

The easiest way to diagnose it is with a Pscan pscan.uk - Diagnostic tool for Rover, MG and Landrover cars this will show you exactly what the SRS system thinks is at fault.

 

[JoCoLo]

I’d agree the rotary coupler is often to blame. Don’t judge me but come MOT time I have opted to go down the resistor across the terminals route. Its what you do if you have a different non airbag steering wheel fitted. A few years ago I squirted electrical cleaner fluid on all the connections and it’s been fine ever since. Still keep resistor handy just in case though.

 

[MidgeVVC]

My '98 F has had this problem for years now. It usually comes on just before MOT is due.
My fix is:- remove air bag (just 2 Torx bolts), disconnect the connector and a squirt of electrical contact cleaner.
Lasts nearly a year.

 

[mowog73]

Don’t judge me but come MOT time I have opted to go down the resistor across the terminals route.

I have a similar problem. What size resistor did you use?

 

[Jimmy_MGF]

No judgement, but the ol' brainbox is ticking now. As mowog73 asked; what size resistor did you use?
My logic is if the SRS system checks itself via resistance, I can go around each seat and rotary coupler trying the resistor on each. When the light goes out, I've found the dodgy component!

It probably is the coupler, but I have a box of resistors in my cupboard so always willing to try a quick and easy test first.

 

[MG54 BAZ]

Try disconnecting the connectors and spraying with electrical spray,the surfaces can oxidise !!

 

[JoCoLo]

2.1 or 2.2 Ohm should do it, you can get a pack from eBay with various sizes from around 2.0. I had to try a few different ones but eventually got it to switch the light off.

 

[Jimmy_MGF]

I'll have to try the resistor trick for Tuesdays MOT
Put in a replacement ebay rotary coupler this morning but still a red light. It could be its from ebay, and it did have a slightly different part number, but it was an MG marked original (picture is the one I took out).

Wish I cleaned the airbag connector as suggested above when I had it off!

Any other suggestions as to what I can try are welcome. SRS fuse, maybe?

Plus side is I know how to pull the steering section apart down to the rotary coupler, and next time I dont need to remove the finicky hooter buttons!

 

[deepfat]

You must have looked at the U Tube vid it nearly led me astray, good luck with the MOT

 

[Jimmy_MGF]

It was a youtube job. How were you led astray?

 

[deepfat]

I said nearly, I watched it prior to removing my steering wheel and thought why has he removed the buttons as they seemed to play no part afterwards. Did some googling and discovered there was no need to remove them so one job saved. Got to say when I did the job it was the first time I have removed an airbag and I was very wary, felt I should have been dressed in a UXB suit!!!
Did you test the continuity of the coupler before fitting? they are a bit fragile so it could still be that.

 

[Jimmy_MGF]

Yeah nearly. Sorry; was in a rush whilst waiting for the petrol pump.
I was thinking about breaking out the ol' multimeter when I get home to check the old one.
At least if I confirm it is broken then the one installed has probably gone too and I just got unlucky. if it does work.. well I put it back in but back to square 1 on the issue!
Cheers, will report back after I've had another play

 

[Jimmy_MGF]

Sorted! Closing post on this one.

Got some 1 Ohm resistors to trial-and-error the system. Before ripping out the steering wheel I stuck 1x 1 Ohm resistor in each seat connector, bridging their terminals. Light when out, so by process of elimination I found the driver pre-tensioner is the problem.

This was incredibly easy to diagnose so I'll likely keep a 1 Ohm resistor in the spare bits box (ash tray) in case the SRS light comes on again.

Resistor values - I first used 2x 1 Ohm resistors on each seat connector as I read 2 Ohm is needed. This works, but as they were just twisted together I then tried a single 1 Ohm resistor and it still worked.
Crux of it is: 1 or 2 Ohm resistors work to test the seat SRS system. Tried a 33 Ohm resistor out of curiosity and that didn't work, so clearly low value resistors are needed.
I didn't try a resistor the airbag connector as there was no need to pull it off, but if someone tries let me know. I expect a 1-2 Ohm resistor will probably work too.

Cost me a few hours of trial-and-error, and £20 for a new rotary coupler, but I now have a spare and the knowledge to replace it again in future!

Cheers everyone!

 

[JoCoLo]

It is an excellent and cheap way to diagnose the SRS system. Mine has been ok for a few years but I keep the resistor in the glove box just in case.

 

[deepfat]

Thanks for closure most don't bother, glad you fixed it and shared the knowledge gained. The good thing is many years in the future when your rotary coupler packs up and they then cost £100+ you have one.

 

[coffeebreakbios]

Most F and TF airbag modules can be well over 20 years old, over this time they lose their prime pressure which either makes them fire weakly or just not fire at all wnen in a collision.
If you buy a second hand one, you can end up in the same situation with a 20 year old unit.
If I was you I would disconnect the plugs under the seats and put resistors in the sockets.and unplug it from the coupler.

My 02 TF 13 spares car had extensive front end damage, the airbag did employ but was too weak to split the plastic on the steering wheel, it just made a white mess round the stalks,,, it was just worn out due to age.

 

[deepfat]

Did the guy you bought it off have a flat nose? seriously most on here (inc me) have no idea what's actually inside them, theory is OK but that's as far as my knowledge goes. I presume there is a cylinder of gas that over time leaks out, is it not possible to have these changed or recharged?
I had a quick look on line and I can get a new drivers air bag for £114 which to me seems about reasonable, but it states they are original MG Rover so does this mean they too are 15/20 years old. Passenger air bags and the seat belt pre-tensioners both seem to be unavailable new so it's SH (dodgy) or recon if available.

 

[JoCoLo]

Did the guy you bought it off have a flat nose? seriously most on here (inc me) have no idea what's actually inside them, theory is OK but that's as far as my knowledge goes. I presume there is a cylinder of gas that over time leaks out, is it not possible to have these changed or recharged?
I had a quick look on line and I can get a new drivers air bag for £114 which to me seems about reasonable, but it states they are original MG Rover so does this mean they too are 15/20 years old. Passenger air bags and the seat belt pre-tensioners both seem to be unavailable new so it's SH (dodgy) or recon if available.

They are not gas, it is an explosive that detonates and makes gas very very quickly. My Avensis is having a new bag fitted next week. It is 18 years old but Toyota are still recalling the airbags. Fitting is free.
I think with time the explosive becomes less and less effective and due to the atmosphere around it weakens.

 

[coffeebreakbios]

I've not found anyone who recharges air bags, they might exist.
As for new genuine spares, these must be new old stock, spares are not made anymore except for after market spares, when were they manufactured? the last tf to leave the factory was 2011, so the manufacture of spares must have stopped then as well, so if it's original, it's still a 12 year old part
Like anything else they do degrade over time.
If you buy an airbag unit, it just might be totally fine, but the only test to find out if it works is when you have a bump.
I've bought spares from many places, but as yet not found any Fs or TFs with the airbags that's been fully deployed.
MMMmmm food for thought.
I've completely disconnected my bags, but I do have 4 way harnesses fitted.
Cheers Ray