New alternator - battery light
Discussion
I've just replaced my alternator but when it got dark last night I noticed that the battery light was lit on the dash; no key in ignition and car locked. On closer investigation I found the alternator was warm. Removal of the belt shows there is clearly current flowing through as it feels like an electric motor does when you twist it by hand (and obviously it's warm!).
I ran the car a bit after installing and was getting a decent voltage at the battery but the unit was whining a bit.
After a bit of searching for help I have verified that the 100 amp fuse is OK by measuring voltage between the main alternator feed on the back of the alternator and a good ground. I got just under 12v (the drain would have been around 5 hours worth so not surprising the battery voltage got below 12v).
If I disconnect the thinner wire, the alternator spins freely so clearly that's where current is flowing.
Based on what I've read, it looks like the alternator could be damaged or faulty however I'm unclear if this is how it arrived or whether something I did caused it. Seemed like an easy enough job and hard to cock up and I'm not a noob when it comes to working on cars. What else I can I do to test it? It just so happens I have a second brand new unit as the seller sent me two by mistake, but I don't want to connect that one up without taking advice, for fear of causing damage to it as well.
When I started the engine there was a whine coming from the alternator but it seems this is sometimes normal depending on what you read. I have to admit it didn't sound normal to me. It's not a famous brand unit so maybe I got what I deserved?!
Any advice appreciated.
I ran the car a bit after installing and was getting a decent voltage at the battery but the unit was whining a bit.
After a bit of searching for help I have verified that the 100 amp fuse is OK by measuring voltage between the main alternator feed on the back of the alternator and a good ground. I got just under 12v (the drain would have been around 5 hours worth so not surprising the battery voltage got below 12v).
If I disconnect the thinner wire, the alternator spins freely so clearly that's where current is flowing.
Based on what I've read, it looks like the alternator could be damaged or faulty however I'm unclear if this is how it arrived or whether something I did caused it. Seemed like an easy enough job and hard to cock up and I'm not a noob when it comes to working on cars. What else I can I do to test it? It just so happens I have a second brand new unit as the seller sent me two by mistake, but I don't want to connect that one up without taking advice, for fear of causing damage to it as well.
When I started the engine there was a whine coming from the alternator but it seems this is sometimes normal depending on what you read. I have to admit it didn't sound normal to me. It's not a famous brand unit so maybe I got what I deserved?!
Any advice appreciated.
Hut49 said:
You didn't mention why you replaced the alternator - if the battery was u/s then it may be the cause of the original issue that is now causing the new alternator problem. I'd get a full check on the battery (not just will it charge).
I've no reason to doubt the battery - it was starting the car fine. I replaced the alternator because the bearings were worn.ric355 said:
I put the old one back on, no battery light with the key off and doesn't feel like an electric motor once connected as the new one does (again, with the key off). Diode pack gone on the new one? If so, question is did I somehow cause it?
Doubtful you caused this fault. Failed diode allowing the current to flow to earth so putting the light on. If left overnight this will drain the battery. N7GTX said:
Doubtful you caused this fault. Failed diode allowing the current to flow to earth so putting the light on. If left overnight this will drain the battery.
As I suspected - thanks. I dunno what I'll do now - the seller sent me two by accident. Perhaps pushing my luck to ask for a replacement !!ric355 said:
As I suspected - thanks. I dunno what I'll do now - the seller sent me two by accident. Perhaps pushing my luck to ask for a replacement !!
I have in the past bought a "new" alternator that had a failed diode. Local auto-electrician got it sorted eventually - the spec was incorrect. I'd try the other one you have been sent by mistake. If both don't work then it is a dodgy batch of alternators - or more probably wrong spec for the TVR.Good luck
FG
FunkyGibbon said:
I have in the past bought a "new" alternator that had a failed diode. Local auto-electrician got it sorted eventually - the spec was incorrect. I'd try the other one you have been sent by mistake. If both don't work then it is a dodgy batch of alternators - or more probably wrong spec for the TVR.
Good luck
FG
I just tested the diode pack using info from a YT vid which says set the meter on diode, +ve on casing, -ve on main terminal, and I should get 500-800mv. Then reverse the leads, and should get open circuit. That test is not for this specific alternator but I got 488mv and open circuit withe the alternator off the car, which tends to suggest that the diodes are working.Good luck
FG
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