Technical Tips > Post 84

C4 1990 "Rest Infl" alarm lights.

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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! :bbq:  its a much better to own  a  pre 73  C3 . :golfer:
Bfit

MY081:
Even better if YOU own a 72 C3 Mr Bfit

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