C4 1990 "Rest Infl" alarm lights.

[Vettech]

Well when I got this 90, it had the red seatbelt alarm light and the Inflation Restraint lights on.
Cant be too hard to fix or can it?
After some research, it appears to be year specific and no one seems to be able to fix it, no new stock or even used parts unless you pay a motza . This is for the Drives Airbag, AND A WARNING HERE, dont work on this circuit unless you disconnect the battery.

It appears there are two crash sensors located on the chassis roughly under battery and under A/C matrix.

Appears they rust (corrode), to fix, remove each, clean rail and sensor base, dielectric grease, refit, cancell codes - all good........
In the meantime I cant find the ALDL socket, so I cant read which codes are set. They have done a LH - RH conversion, I hope they did not cut it off!?
So I chose the hardest (RH under A/C fan matrix) to see, for this job you need multi multi jointed fingers and hands, plus more patience than I.

Got it - cant check it because then I had no internal cct diagram, (now 12 months later I do), it looked ok, had grease, clean umm very strange.
But cant reset codes as I cant find the ALDL Socket. Placed in tooo hard basket for now.

[Vettech]

Well today I removed the LH side under dash covers, and Wallahhh, I find the ALDL SOCKET - I now have computer access.

Run codes - ummmm bs I knew it - got a 16 and a not expected 42?...... the 16 means the defective sensor is............ yes you guessed it, the LH side, the one I did not do. But whilst researching the 42 (yes I know - Life, the Universe and Everthing) I found that this earthing check the computer does is to ensure that the two sensors are actually fitted to the chassis rail, WTF, did they expect some one was going to steel them, they are neigh near impossible to get to let alone off.

Any way I tried several times to reset the codes, no luck, but then I read that the plug/socket on the end of these sensors has no clip lock (?) so if it comes apart, it will give the same result as O/C earths, and of couse this car is converted, admittedly a very good looking conversion, but it comes thru the fire wall right where the S'column and pedals used to be on the LH side.

Run out of light, patience, back muscles, hand skin, best save some for another day.
I did also find out that once cleaned etc the resetting of the codes was not an easy task.....

I actually started all this because the high level 3rd brake light is not working, its on a seperate cct off its own switch on the brake pedal, yes the pedals that have swapped sides in the car. Good chance the plug is out or cut off or or ......

[Vettech]

This tread only applies to the 90 year model
Any cable with a "Yellow" jacket is part of the Air Bag cct and must be treated with care.
Before working on it, disc battery and deaden cct for at least 10 mins

If you clean the earth, and want to check the Sensor internals - below is a cct.

Ensure if you use an Ohm metre that you disc the sensor from the Air bag or DERM

[bfit]

This post  make me think!   its a much better to own  a  pre 73  C3 .
Bfit

[MY081]

Even better if YOU own a 72 C3 Mr Bfit

[Vettech]

Hahahahaaaaaa ha!

I love it when a plan comes together. What a great day.

I ripped the LH 1/4 panel off, battery out, battery holder, and there it is, the LH airbag sensor.

BUT - RIGHT NEXT TO IT ARE TWO EARTHS !?..

So chassis cleaned, greased, but the earths are now tied to the sensor via its small bolt.

Took a few goes to reset the computer, but now the "INFL REST" and the little red seat belt man are GONE.

Time for a G&T icy cold......... or two............

Oh and your wrong its better to be driving a Rocket Sled than a bucket of squeaks.............

Now for the job I was originally looking to fix -the hi level third brake light...

[Vettech]

So much for the plan coming together.
On the way to Port MacQ last week the "REST INF" and the little red seat belt man came on again.
Thats a PITA.

Left it till today, between showers I interogated the computer via the ALDL socket.

Only one code - "26"    thats the RH side sensor - defective earth. (Possible)

OH well in hindsight, this side was originally a PITA, ended up with more holes in my hands/arm leaking my red transmission fluid than a colendar.

So this time I'll remove the 1/4 panel, wheel, inside wheel guard, washer bottle, overflow bottle - then maybe I'll get a hand onto the sensor.

I think I will make a good lead with crimped/soldered ends so I can run across to the LH side and pick up the earths on the LH sensor.
This will tie all the earths together and the LH  one also ties straight to the Neg battery terminal.

If that dont fix it, then I dont know what will, maybe look at the 91 model ccts to see the differences, but I think its safe to assume the 91~ have different computers and software.
Regards.

[Vettech]

Back Again.
As already explained the C4 90 is the only year that has this SIR/ Airbags issue, caused by an idiot designer. (Sorry I call a spade a spade).
The resultant alarm displays the "little red seat belt man" and the "rest infl" lights.
In theory these lights should negate your pink slip & rego.

Now that I've repaired all else, I will tackle fitting a purpose made lead that according to my little grey cells, should rectify this issue.
 
Keep in mind that my sensors etc are all working OK, it's the inadequate cabling, earthing & connections that causes this ECM derived alarm situation to be displayed.

Not a five minute job as the quarter panels, inner guards, battery and its holder etc etc have to be removed, but I believe this mod should overcome these alarms - keep you posted.