MGB GT Red Warning Light - Dashboard
Discussion
Hi All,
I have a question regareding the red light that has recently come on. Its the red one of the two lights the other is blue for the high beam.
As I understand it the red light is luminated when the battery is not being charged by the alternator. IS this the light's only function?
The red light on my dashboard is intermittant, though normally its either shining brightly or fades out to just barely being on. I have noted that in one instance everytime I engaged my overdrive that the light went on, and went off when i turned the overdrive off.
I have tested the battery, and it is 12 volts without the car running and then giving a reading of 13ish with the engine running, so this points to the battery charging and the alternator etc therefore working.
Any ideas? or any gaps on my knowledge?
I have a question regareding the red light that has recently come on. Its the red one of the two lights the other is blue for the high beam.
As I understand it the red light is luminated when the battery is not being charged by the alternator. IS this the light's only function?
The red light on my dashboard is intermittant, though normally its either shining brightly or fades out to just barely being on. I have noted that in one instance everytime I engaged my overdrive that the light went on, and went off when i turned the overdrive off.
I have tested the battery, and it is 12 volts without the car running and then giving a reading of 13ish with the engine running, so this points to the battery charging and the alternator etc therefore working.
Any ideas? or any gaps on my knowledge?
Assume that it is an alternator that you have and not a dynamo, as with the latter, you will get a faint glow at low revs?
The red light is indeed the ignition warning light, which indicates when it is "on" that the charging circuit is not delivering suffice voltage to the battery; when it is off the charging voltage is being delivered above the minimum requirement. You should not see the light on or "glowing" at all when the engine is running. The charging voltage (i.e. what a voltmeter reads when put across the battery terminals with the engine running should read somewhere more towards 14v than 13v.
The light bulb itself works so that isn't the issue. Following are thoughts as to what it could be, in a sort of order to check:
1) The intermittent nature of it and the apparent connection to the overdrive could point to a dodgy earth somewhere in the charging or ignition circuit, as the current seeks an earth path through something else. As well as physically checking connections at the back of the alternator for loose spade connectors, frayed or exposed wiring etc, loosen the alternator mounting bolts and check that the faces of the mounting plates to the engine block and the block where they mate to are clean and paint/corrosion free points/bolts of the alternator are clean and tight.
2) Check the ignition switch itself for bad/corroded/loose wires/connections (and does the key switch assembly feel worn and loose when you use it when starting the car?), as another cause can be bad connections in the white/brown wires circuit to/from the ignition switch, as this would cause a low voltage on the white wire to the light.
3) Finally, it could be that the voltage control pack on the alternator is failing - check to see what voltage is being output from the thick brown wire coming out of the plug at the back of the alternator (remove the covering cap if there is one but leave the plug plugged in). If you see higher than across the battery terminals, the thick brown wire somewhere between the alternator and where it picks up the main current cable to the battery (i.e. at the starter solenoid) is the culprit. If the reading is the same as the one across the battery then it is likely to be the voltage control pack which indicates a need to replace the alternator (but of course you can get that element checked easily by an electrician to make sure before buying).
MG Mark
The red light is indeed the ignition warning light, which indicates when it is "on" that the charging circuit is not delivering suffice voltage to the battery; when it is off the charging voltage is being delivered above the minimum requirement. You should not see the light on or "glowing" at all when the engine is running. The charging voltage (i.e. what a voltmeter reads when put across the battery terminals with the engine running should read somewhere more towards 14v than 13v.
The light bulb itself works so that isn't the issue. Following are thoughts as to what it could be, in a sort of order to check:
1) The intermittent nature of it and the apparent connection to the overdrive could point to a dodgy earth somewhere in the charging or ignition circuit, as the current seeks an earth path through something else. As well as physically checking connections at the back of the alternator for loose spade connectors, frayed or exposed wiring etc, loosen the alternator mounting bolts and check that the faces of the mounting plates to the engine block and the block where they mate to are clean and paint/corrosion free points/bolts of the alternator are clean and tight.
2) Check the ignition switch itself for bad/corroded/loose wires/connections (and does the key switch assembly feel worn and loose when you use it when starting the car?), as another cause can be bad connections in the white/brown wires circuit to/from the ignition switch, as this would cause a low voltage on the white wire to the light.
3) Finally, it could be that the voltage control pack on the alternator is failing - check to see what voltage is being output from the thick brown wire coming out of the plug at the back of the alternator (remove the covering cap if there is one but leave the plug plugged in). If you see higher than across the battery terminals, the thick brown wire somewhere between the alternator and where it picks up the main current cable to the battery (i.e. at the starter solenoid) is the culprit. If the reading is the same as the one across the battery then it is likely to be the voltage control pack which indicates a need to replace the alternator (but of course you can get that element checked easily by an electrician to make sure before buying).
MG Mark
Edited by MG Mark on Wednesday 15th September 22:11
I'd also suggest you buy a owners Handbook as it tells you no end about the car, instruments and servicing
http://www9.mgcars.org.uk/cgi-bin/gen5?runprog=mgo...
As well as what Mark's put above, to complete the job I'd also check the main leads and connections to and from the battery, disconnect and clean all the terminals, the battery lugs and fixing pionts, nuts, bolts and washers and copperease everything before reconnecting include the earth wire that goes from engine to body
If you have two 6v batteries especially do the joining wires and connections and and include the long live wire from battery(ies) to solonoid
Replace any wires or connectors that are suspect especially the battery and one to soloniod
BTW if your overdrive doesn't slip in and out almost immediately you can clean its filter - again info for this in the owners Handbook IIRC
http://www9.mgcars.org.uk/cgi-bin/gen5?runprog=mgo...
As well as what Mark's put above, to complete the job I'd also check the main leads and connections to and from the battery, disconnect and clean all the terminals, the battery lugs and fixing pionts, nuts, bolts and washers and copperease everything before reconnecting include the earth wire that goes from engine to body
If you have two 6v batteries especially do the joining wires and connections and and include the long live wire from battery(ies) to solonoid
Replace any wires or connectors that are suspect especially the battery and one to soloniod
BTW if your overdrive doesn't slip in and out almost immediately you can clean its filter - again info for this in the owners Handbook IIRC
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