Post by Foz on Jul 18, 2014 6:21:12 GMT -5
Hi,
I have been melting my brain recently trying to solve an issue with my Cob which commenced when I went to collect my 14 year old daughter from school. So in front of the whole high school I discovered I had no volts - to anything. Of course being only a short run I had no tools with me so thinking it would be a fusible link/main fuse issue I set to visually fault finding the issue. This then turned into having a tow truck take us home with 'so embarrassing' being voiced by my daughter several times.
The next day I attended to the issue with gusto (and tools) but failed to find the 'simple' obvious' problem. Taking a break for lunch and a cold beer it dawned on me that the negative connection to the chassis might be the issue. Ta Da!! A broken cable lug right at the connection to the chassis from the battery. No problem, new lug crimped and soldered on the cable, chassis connection point cleaned up and the cable bolted on. Done and happy. ..... Or so I thought.
Fired her up no trouble and glanced at the ammeter to see the needle not return to '0'. Hmmm
??
Out with the multimeter and measured the volts directly from the alternator to discover that the volts remain the same as the battery at 12.5V ish. Revved the engine and the volts drop slightly. At this point I think that the rectifier circuit in the alternator is damaged due to open circuiting the negative.
Out comes the alternator which is a pretty well standard 85 amp internally regulated Bosch unit. Strip it down thinking that a diode or two my be dead but after testing everything except the regulator all seems fine. Must be the regulator I think to my self so I get one, reassemble the alternator and replace it into the car to discover the condition is unchanged. Hmmm??
Whilst I am pretty competent with this kind of thing being an electrician my brain had been left wanting so I sent it off to my nephew who is an auto electrician with a test bench. He ran the alternator on the bench and all is good so he sends it back to me with the appropriate 'comments' about his uncle being unable to put an alternator in a car.
Given it is a 3 wire connection. Battery+, S (excitation) and L (dash light) I thought I would recheck that the alternator is in fact getting excitation volts which it does.
So at this stage I am stumped and would appreciate any feedback or suggestions.
I have been melting my brain recently trying to solve an issue with my Cob which commenced when I went to collect my 14 year old daughter from school. So in front of the whole high school I discovered I had no volts - to anything. Of course being only a short run I had no tools with me so thinking it would be a fusible link/main fuse issue I set to visually fault finding the issue. This then turned into having a tow truck take us home with 'so embarrassing' being voiced by my daughter several times.
The next day I attended to the issue with gusto (and tools) but failed to find the 'simple' obvious' problem. Taking a break for lunch and a cold beer it dawned on me that the negative connection to the chassis might be the issue. Ta Da!! A broken cable lug right at the connection to the chassis from the battery. No problem, new lug crimped and soldered on the cable, chassis connection point cleaned up and the cable bolted on. Done and happy. ..... Or so I thought.
Fired her up no trouble and glanced at the ammeter to see the needle not return to '0'. Hmmm
??Out with the multimeter and measured the volts directly from the alternator to discover that the volts remain the same as the battery at 12.5V ish. Revved the engine and the volts drop slightly. At this point I think that the rectifier circuit in the alternator is damaged due to open circuiting the negative.
Out comes the alternator which is a pretty well standard 85 amp internally regulated Bosch unit. Strip it down thinking that a diode or two my be dead but after testing everything except the regulator all seems fine. Must be the regulator I think to my self so I get one, reassemble the alternator and replace it into the car to discover the condition is unchanged. Hmmm?
?Whilst I am pretty competent with this kind of thing being an electrician my brain had been left wanting so I sent it off to my nephew who is an auto electrician with a test bench. He ran the alternator on the bench and all is good so he sends it back to me with the appropriate 'comments' about his uncle being unable to put an alternator in a car.
Given it is a 3 wire connection. Battery+, S (excitation) and L (dash light) I thought I would recheck that the alternator is in fact getting excitation volts which it does.
So at this stage I am stumped and would appreciate any feedback or suggestions.
