12 replies to this topic

[Ozymandias]

My Min is a '95 Jap export Spi.

 

Normally when I turn on the ignition, there's a warning buzzer that beeps for half a second and then goes off.

 

Last couple of days the beep has got longer - a couple of seconds - and then this morning it started beeping randomly (sometimes quickly, sometimes for a few seconds) as I went along (and sometimes whilst idling)

 

Is this a catalytic converter overheat alarm? If so how bad is it that the cat's overheating? What might be causing the overheat, can I do anything to stop it getting so hot or is it time for a new cat?

 

Thanks for any advice/help!

 

 

[spiguy]

It is likely that it is the cat overheat warning alarm. I removed this from my car when I changed the cat back to a playmini. Mine wasn't behaving oddly at the time however!

 

every chance that it is a fault with the system itself, if the car is running well etc. It is basically a PT100 temperature probe. I don't know what the warning temperature limits are, but if you could find out then maybe you could use an infrared temperature gun aimed at the cat to see if it is just a false alarm (I suspect it probably is).  It could be a wiring issue - the thermocouple wire runs up along the floor, then up into a box which in my case was mounted to the left hand side of the instrument cluster bracket (just hidden by the carpet / dash). The sounder in my case was mounted on the other side of the instrument cluster bracket.

 

You could inspect for breaks in the wire, or a bad connection at the box of tricks. Is it a requirement in your country?  It isn't in the UK and isn't fitted to any of the UK minis.

 

I am tempted to say just ditch it, and that is what I did. But it would be nice to establish that the CAT isn't 'overheating' before doing that I guess. Any running issues? Plugs the same colour as normal?  Engine temperature normal? What about the smell of the exhaust - any strange new smells?

[Ozymandias]

She's running fine ever since I replaced the dodgy coil - although all that misfiring before I did might have fried the cat!

 

I'll check the plugs and exhaust smell over the weekend - certainly the coolant temp gauge is reading fine. I've probably mashed a wire somewhere and it's shorting.

 

I've also got to get the screen and dash out over the weekend, so that'll give me a chance to look at the wiring behind the dash.

 

Do you remember what colour wires come from the thermocouple?

 

Cheers!

[brivinci]

Wow, never knew these cars ever had such a think. What else, aside from AC of course, did these Jap exports have on them that the cars in the UK didnt get?

[spiguy]

If you lift the carpet you should see it - it will enter the cabin somewhere up the front - in my case passenger side front footwell, through a hole which was then siliconed around. The temperature sensor wire is a white glass wrap insulation type thing, can't miss it - it looks totally out of place!

 

Alternatively to trace it, look under the car at the CAT and you will see the cable coming from the sensor, it will then be secured to the floor pan in several places before entering the cabin. It runs up the toeboard and up behind the dash. Should be easy to trace, there's nothing else like it in that area.

 

Initially when I got the car, I hadn't yet figured out where the sensor box / sounder were, so I just cut the wires under the carpet and soldered in a 100Ohm resistor. This had the effect of fooling the thing so that it wouldn't beep constantly as I had the play mini (with no sensor fitted). Still gave the single beep with ignition on, to tell you the systemis working.  Eventually I was poking around in the dash area when I found the box and the sounder box. I was wiring in gauges, so it was a convenient opportunity to remove it and steal it's 12V supply for the gauge light!

Edited by spiguy, 04 September 2015 - 10:26 PM.

[Ozymandias]

I think it's sorted - it kept beeping on the way home on Friday, so I gave the dash a hefty thump and it shut up!

 

It still beeps on turning the key, so it must have been a dodgy connection somewhere...

[spiguy]

Sounds like it. If bashing the dash helped, that suggests a poor connection where the temp probe wires connect to the 'black box' which is mounted on the left side as you sit in the seat (on a right hand drive mini) of the instrument cluster bracket. Might be worth having a look. The wires are probably into screw terminals, maybe one has loosened off.

 

I would be tempted to just ditch it, though you would need to either replace the cat back part of the exhaust or fit a blanking plug / bolt to the sensor hole. Alternatively  you could just remove the electronics bits and leave the sensor in place.

[Ozymandias]

It does make me wonder why they went to all the trouble of putting in a beeper (which, with its associated electrics, is expensive) when a simple warning light would have done the job and would only have cost a light bulb and a holder!

[FlyingScot]

Probably because they had to meet some specification or regulation...

FS

[spiguy]

I suspect the thinking is that a loud audible alarm will force you to take notice of the situation (ie if the cat is overheating) whereas people would probably just ignore a light. It's bloody loud and annoying when it goes off!

 

I suppose that an overheating CAT must be seen as a fire risk and that justifies taking it more seriously. Make you wonder though, why don't other countries require this if it's such a big risk !?

[FlyingScot]

Nothing to go on fire really unless you park it over grass....

The cat is ceramic, the packing is ceramic fibre and the can is metal. The heat shield is ceramic or PCW mat.

I have seen they glow cherry red when misfuelled thought

FS

[Ozymandias]

Nothing to go on fire really unless you park it over grass....



FS

That's good to know...!

[Ozymandias]

It turned out to be a short in the wiring loom - I haven't managed to find exactly where it is, but fiddling the wires stops it most of the time. I've disconnected the buzzer and put a dash-mounted red warning light in - I was getting fed up with driving on long journeys to an intermittent soundtrack of "BEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP!"

 

Edited by Ozymandias, 09 June 2016 - 11:32 AM.