Ignition warning light problem........

[Hedgehopper]

My '97 500 has ignition and oil pressure warning lights built in to the bottom of the speedo and both work normally. Between the speedo and rev. counter there are three more lights, the top one of which, according to the handbook, is another ignition warning light. However, this light does not work in the normal way that the other one does (on with with ignition switch then off once engine runs). This light only comes on the moment you turn the engine off and then only for a brief flash. At all other times it remains off.
Whilst removing the dash for re-veneering I took this pic. of the wiring to this warning light. What is the small grey block, with 470R 5%E written on it, for? Also, I believe LEDs only work with the connections the correct way round. As the LED bulb terminals are not marked how do I know which is correct? Could this be the cause of the problem?

[PeteGriff]

Hedgehopper said:

My '97 500 has ignition and oil pressure warning lights built in to the bottom of the speedo and both work normally. Between the speedo and rev. counter there are three more lights, the top one of which, according to the handbook, is another ignition warning light. However, this light does not work in the normal way that the other one does (on with with ignition switch then off once engine runs). This light only comes on the moment you turn the engine off and then only for a brief flash. At all other times it remains off.
Whilst removing the dash for re-veneering I took this pic. of the wiring to this warning light. What is the small grey block, with 470R 5%E written on it, for? Also, I believe LEDs only work with the connections the correct way round. As the LED bulb terminals are not marked how do I know which is correct? Could this be the cause of the problem?

Hi Hedgehopper, the grey block is a ceramic cased resistor (470 ohms). If it is connected to the LED type bulbs it is to restrice the current flow to the LED bulb. Others may comment on other definite reasons for it by with my engineering head on that is my opinion. Regards, Pete

[paulathome]

As above its a 470 ohm resistor to limit the current through the LEDs.
As for the LED itself it will only light up if its wired the correct way round. No harm will be done if it is the wrong way round
It will just not light up. From your symptoms I would say its the wrong way round.
Paul

[Hedgehopper]

Thanks Paul and Peter. I understand what you're saying, but why don't the other two warning lights have this resistor as well?
Have just noticed that the terminals on the LEDs are different, one is brass plated and the other plain. Is this supposed to indicate polarity and if so which is which? It's hard enough not to damage the trim getting the dash back without having to remove it again to change the polarity!
Sorry about all the questions...but your help will be appreciated.