75ZT Community

Is there any way of tracing a faulty under seat connector for the airbags?

I have cleaned both the passenger and drivers side, but still the Airbag light will not go out.

I've recently had this and it ended up being the rotary coupling behind the steering wheel!

If you can, try and get the car on a T4 (Testbook version 4.Computer Diagnostic System), to see if the fault can be found, but I ended up hard wiring the wires under the seats, changing the SRS (Supplementary Restraint System) ECU (Engine Control Unit) (which is a bugger to get to), the pre-tensioners and thankfully changing the rotary coupler, thankfully sorted it!

However, a word of warning, especially if you do a lot of Town driving, (as Ed does), don't be tempted to fit a used rotary coupler as I did, as of course, it'll be unlikely that it's a lot better than the one it's replacing, as Ed's has now gone again, so I aim to replace with a new one from Rimmers, before the next MOT!

Mike make the Nano and we can help you get it sorted, it is most likely sensor under the carpet it may have corrosion set in, also fit some new connectors I use if i change the connectors, i have a few made up somewhere.

Arctic wrote:Mike make the Nano and we can help you get it sorted, it is most likely sensor under the carpet it may have corrosion set in, also fit some new connectors I use if i change the connectors, i have a few made up somewhere.

Car is presently under SORN so can't make the Nano-Meets as no MoT. I have cleaned the connectors under the seats together with the pretensioners. I have joined the wiring directly together and used connectors but no luck, light is still showing.

I have a new steering wheel rotary coupler, so I will replace the original with this.

Is there a how to anywhere covering the removal and replacement of the coupler?

Bermudan 75 wrote:I have a new steering wheel rotary coupler, so I will replace the original with this.

Is there a how to anywhere covering the removal and replacement of the coupler?

It's not a difficult job, as even I've replaced one!

Remove the airbag from the steering wheel, (from memory, 3 screws on the back), remove the steering wheel, which is of course just one nut in the middle, remove the indicator and wiper stalks, (2 screws each) and then that give you access to the rotary coupler, which is held in with another 4 screws.

The only problem you may have, is that most of the screws are Torx style screws, so unless you already have them, you may need to purchase the right size ones to remove the screws.

Sorry, I can't remember which size they are, off the top of my head!

You need to remove the cowling too around the steering column.

You can take the four screws out of the switch and rotary coupler as an assembly, and then take off the switches if it's easier. There are two torx screws holding the airbag on. You can see the four torx holding the assembly on in my photo. They can be quite stiff.

Most important point: once the airbag is off, straighten the wheel and check the front wheels are facing absolutely straight forward. When you fit the new coupler you need to check it is set central. If you look at my photo you can see a little window to the left of the the central hole. In my photo there is a lttle white rectangle showing. It must be in that position when you fit it and put the wheel back on. If yours shows black in that window you must carefully turn it until the white bit appears. If it gets to then end and hasn't shown, you need to go the other way. That's why you have to be really gentle when you do it.

Finally take care when loosening and tightening the bolt that holds the wheel on. It's tight and its very tempting to use the steering lock to hold the wheel still while you tighten / loosen it. It's much less likely to damage the lock if you leave the key in and get someone to hold the wheel still for you.

Duncan wrote:

IMG_4380.jpg

You need to remove the cowling too around the steering column.

I knew that I'd forget something!

Thanks for the replies folks. I have replaced the rotary coupler with a new one, but the light is still on.

I am now in the process of checking the side impact sensors and will disconnect them and give them a good clean.

However how do these connectors release? I don't want to damage them. Mine are the later orange ones mounted on the inner sill.

Photographs I have seen don't give away to much about how these connectors are released.

I managed to disconnect the sensor, it has been cleaned with contact cleaner and reconnected. The sensor and surrounding area is dry and there is no evidence of any water damage.

So a duff sensor is not the cause of the light still being illuminated.

Looks like I will have to book the car in for a T4 session and MoT. That will be after the cracked windscreen has been replaced.

Not looking hopeful that I will get the car to a Nano-meet this year.

The sensors can fail and still look perfectly OK. The only non-T4 test is substitution. If you do that, make sure the test sensor is in the same orientation as the one on the car, or in can still leave the light on. Presumambly it thinks the sensor must be faulty if it tells the ECU that the car is upside down.

Thanks for that Duncan, the sensors in the car at the moment are the orange ones, can they be replaced with the green ones?

I'm not sure but I think the plugs are different.

No the green early ones cannot replace the orange ones, I am also not sure but I heard somewhere the tourer ones are also different from a saloon?
1

I have got a pair of replacement orange ones, I will try these to see if they cure the problem.

A Nano regular had the same problem he had to cut his plug of the main loom and add another die to water damage, I am not saying that is your problem, but worth keeping it in mind look for corrosion in the plugs of the loom, with a torch.

I plugged the car into a PSCAN and it can up with the following:

2 error codes

Current 0805 Circuit 5 resistance too high
Current 0809 Left front side airbag resistance too high

Circuit 5 applicability
Front seat belt tensioner

I have wired the airbag directly to each other and the PCSAN still shows the fault.

Does the pretensioner need replacing?

Mike

I had similar after fitting sports leather to my 190 and the pre-tensioner did in fact need replacing, the car that the interior had come out of, had obviously had quite a hard bump, before I bought the interior. However, after replacing the pre-tensioners, I was still having problems with the light and it ended up being the rotary coupler, which after fitting a couple of used ones, I ended up fitting a new one from Rimmers, which finally sorted the problem! Have you had the car on a T4?

The rotary coupler has been replaced with a new one.

Bermudan 75 wrote:The rotary coupler has been replaced with a new one.

How about the SRS ECU?

On later cars, it seems the two pretensioners on the front seats are wired in series for some reason. On a T4 when this is the case the fault is listed as series pretensioner. That means that the fault code doesn't identify which seat has the problem. So check both in case yours is one of those. This caused my confusion on Bernards V8 for a while.