Hard top heated window light on all the time

Hello I just put new battery on the old girl as she's been stood for 5 month now and her old one was done in. everything is good fired up right off the dot but my heated rear window light is on all the time I tried another switch that I had and this is the same could the relay be sticking ??? can I clean this or is it time for a new one thanks

My mg stood for 5 months put a new battery on and the alarm would keep going off. Went round all locks with wd40 sorted it.

All the time all the time
or
all the time when the ignition is on all the time or
or
all the time when the engine is running all the time?

Its on all the time even with key out I have taken the switch out save it running battery down any ideas ??? I have a replacement relay might pop it in later if I have chance
:omg: :omg: :omg:

The relay should only be energised when the oil pressure switch is reading pressure so that the HRW only works when the engine is running, my guess is the oil pressure switch has stuck open allowing the relay to be on all the time. Might be worth checking the oil light is on with the ignition on and the engine off.

The quick remedy is to pop the relay but I'd be checking the oil pressure switch, especially as this can effect other systems with in the ECU.

ok how to I check replace is this a easy job to do cant say I even Know where it is located???

It should be a simple spanner out/spanner in job but I suspect it will be only accesable from the engine cover.

Unless I'm missing the point here, you need to establish whether there is 12V being presented to the HRW elements or whether the fault is the indication circuit only.

The HRW itself is only energised when the motor is running, not just when ignition is energised as with most cars that are not designed and built by Brummies.

If there is 12V at the rear window terminals when the key is out there is a hard fault.
If not it is an indication fault.

Stuff a meter into the terminals and measure with Ign off.

Let us know your findings.

The plug has power all the time I changed the switch and the new one was lit up all the time even with keys out random any ideas I haven't had time to pop the relay out not sure where the oil pressure switch is to check or replace ????? I have just disconnected the switch for now so its not lit up all the time

Hey everybody....just wanted to know if you still have the same problem. i.e. is your HRW on all the time.

I had the same problem and after extensive troubleshooting and wiring checks (thanks to http://www.mgfcar.de/schedules/ and attached) the problem was with the Multi-Function ECU. This is the box mounted behind the fuse box with the part number YWC104500.

It seems that the relay for the HRW is powered from this box, (pin 4 from memory of the big plug). The problem for me was this box had failed and was constantly supplying 12V...even with the key out of the ignition (same as your defect). The light in the HRW switch is just the tell-tale to tell you that 12v is being supplied to the HRW...that is why it stays on all the time.

Thanks for that, it's very good to know.

Hello sorry for the Very slow response Glen I never did get round to sorting it out were you having problems with your battery draining from this I have a feeling that it is the same problem you had is the Multi-Function ECU right under the fuse box if so will try get it sorted soon I want to get the old girl back out and about.