SRS light on

Hello, new member here
Just spent a happy couple of days trying to extinguish the SRS light, which stays on. Followed the recommendations of under-seat connectors as frequently posted on this forum; without success. Connections good, clean, all wires tight. No amount of fiddling, disconnecting & reconnecting would extinguish the light.
From idle interest removed the SRS fuse from fuse block (bright yellow, extreme left on the fuse board). Could see it wasn'r blown so put it back. Ergo, SRS light came on as it should as it went through its self check then went out momentarily . . . only for a second or two . . . then came back on again. But the fact it went out even for a moment suggested the problem was in some way at the fuse box because that was the last thing I'd done, so took the fuse out again. I noticed the blades were a bit !dull looking" so cleaned them back to bright shiny metal, replaced the fuse and lo-and-behold the light went out and stayed out ! Tried it half-a-dozen times . . . . light going out as it should everytime.
Can only assume the fuse blades can build-up sufficient surface resistance from gradual oxidation to prevent a full 12 volts to reach the system, no matter your battery might be top-notch
The reason for this post is of course to say the first port of call for anyone with a SRS ligth on is to remove and clean the guse blades first. It takes two minutes and in my case was the cause of all the problem. Could have saved myself two days frustrating head-scratching if I'd been aware of that at the start

Thanks to both Paul & Alec. The cleaning of the fuse blades is very interesting, a yellow fuse is rated at 20a, which implies an amount of quiescent current. If the oxide buildup was excessive, the voltage drop could easily be sufficient to prevent a full boot up self test & a fail.
I might measure the current when I’m home.
Alec, I need to look at a few diagrams before I would be happy to put my money into the ‘410. There are through pins that take signals other than airbag & horn. Granted these are all that our cars, in standard form use. My car uses supplementary pins for things such as steering wheel audio controls.
Whilst writing this I’m reminded of a member who bought what he thought was a one for one replacement. It was new & I seem to recall around £25-00; although it metered through it didn’t work.
A replacement from another source cured his problem. The budget replacement was incompatible.
If it was you, could you verify; this could form another frame in the ever changing MG moving picture show.
M

i put my reg in on ebay and it came up with both but mines a 98 f

Thanks again Alec, I don’t doubt you for one moment, I need more persuading when eBay is involved.
I’ve entered the registration number for my 98f into searches, to be informed of compatibility problems on devices I know to function perfectly.
When I’m parting with money I like to be sure the transaction is as water tight as a ducks arse.
M

Thank you AP and Paul. I am paranoid about fiddly parts like this. I will probably go for something with an MG badge and sold as YRC100300.
The same kind of thing was also used on modern Minis, I believe and no idea if there are any differences.

However, cleaning the under seat connector and the fuse is now the first point of attack.

Despite the lurgy, I made it into work today. A cool start with no SRS light but the return at 16.30 was in full sunlight and yes, the light was on.

I will report findings.........

Dave

I'm a complete Dummy First Class when it comes to electrics but to clear-up a possible misunderstanding . . . the SRS fuse isn't itself yellow, thtat's the colour of the plastic shroud which clips over it . . . . can't miss it, it's the extreme left on the fuse board.
And it's rated 5 amp, not 20 amp (at least mine is )

Ah, that puts a slightly different complexion on the situation. The comments on voltage drop are still valid & the inability of a dirty fuse blade to pass the correct amount of current during self test is still to be considered.
That type of fuse & holder are classed as self wiping joints; the act of removing & replacing cleans both fuse & holder.
Hence when a fuse is removed & replaced the contact points are cleaned & hopefully it’s capacity to pass the correct amount of current is restored.
M

Maybe the cause is repaired.

O/S underseat connection is secure but the N/S removed itself as soon as I put my hand under the seat to find it.
The seat had to come out and the connector is now double tied as I think the latch has broken/worn/NIS.

The hood had to come back to reduce working temperature in the cabin so I cannot say it is fixed but the light extinguished on starting.

The rotary coupler replacement is on hold but not forogtten until the light is back on again. MOT in August and plenty of time to do that job at my leisure.
 

Thanks for the help on here.

Dave 

I posted too soon.
Went back to the car today, SRS light staying on again.
What on earth could cause the light to go out when I switched on yesterday a dozen times or more after cleaning the fuse blades, but then stays on today ? (That said, today it stayed on 48 times out of fifty, but did in fact go out twice )
With those symptoms a bad connection is surely favourite . . . . . but where ?

Next up . . . . . my multi-meter reads 12.8 volts across the battery terminals, so that's OK
But when I put it on the SRS fuse holder terminals it only registers 7 volts.
That doesn't sound right does it ? . . . . .does anyone know how many volts I should be seeing at the SRS fuse ?
Am I on the right or wrong track here ?

You should see nothing less then 12 Volts. Can you remined us what car you have (F or TF), what yaer of production with Lucas or Pektron fob?

Many thanks indeed, I thought 12 volts was required but needed a more knowledgeable person to confirm it
The car is a Dec '96 (Reg '97) VVC, Lucas fob I think, not sure of the difference (square fob).
So, this low voltage is 99,99% the cause of the grief . . . . as the battey is good I guess its a question of tracing the wiring back to source. . . . any thoughts please on what & where might be causing the voltage drop. ? There only appears to be the under-bonnet fuse box between SRS fuse & battery