Alternator Probs AQ130

"Can anyone guide (that wo

"Can anyone guide (that would be idiots guide) me through fault finding why my alternator is not charging the battery ? I get the red warning light on as soon as the engines starts and it then stays on. I have checked the main fuse on engine and its ok. If I have a bad earth how could I tell. Ive tried following the wiring diagram but get lost after the circuit reaches the ignition key and instrument panel. I have three wires going to the alternator Red, Blue & Black. Any help greatly appreciated ??? Ps battery is a 12v / 110 amp."

"Put a voltmeter on the fat re

"Put a voltmeter on the fat red wire coming out of the alternator, take a reading (should be about 12 volts) and start the engine. Did it go up? If not, the alternator is shot.

Jeff"

"The blue (purple) wir

"The blue (purple) wire must have + voltage, as it is for the alternator excitation."

"Yet again brill, I did the te

"Yet again brill, I did the test when the engine was not running and got 12.4 V but i did not run the same test when it was running. I will do this in the morning and let you know the outcome tomorrow. Its about midnight here in the UK so im gona call it a day, having had a few glasses of wine im gona take my saw hands, knees and back to bed. Thanks to you both yet again Ile let you know how i get on tomorrow. Have a good day, night or morning depending on what part of the world your in ok."

"Followed your instructions to

"Followed your instructions to the word and found that the reading on the 1st engine was 11.5v stopped, then 11.5v running. Checked the blue which gave me around + 1.28v. Stripped down the alternator to see if there was anything obvous but still the same reading when I re-tested it after. 2nd engine much the same except the blue wire had been spurred off to the engine casing aswell which i found a little strange. I disconnected the blue to the engine casing just leaving it to the back if the alternator but got all same results. Go on give me the bad news ?"

"What alternator do you have?

"What alternator do you have? Is it an SEV Marchal? If so, try to run a wire from the + of the ignition coil to the terminal where the blue wire is connected, then measure voltage at battery again.

If you disconnect the blue wire, your alternator will never work, as it is needed for field excitation."

"Think I may have confused you

"Think I may have confused you. What I meant was on one engine there is simply a blue to the alternator yet on the other there is a blue to the alternator which then goes from the connection on the alternator to the engine casing. It was just the engine casing one i disconnected to make the wiring the same as the other engine and see if it made any diference. Im not sure what make they are but they both different, i will check and let you know ok.Is the ignition coil the black tube type thing by the distributor ?"

"Sorry, my mistake. According

"Sorry, my mistake. According to the drawings from Volvo, the blue goes to ground, the red goes to the large post of the starter, and the black goes to the charging light."

"Now im a little confused cos

"Now im a little confused cos on 1 engine the blue goes to the male connector on the reverse of the alternator only and on the other engine the blue goes fistly to the male connector on the reverse of the alternator then jumps from that (connector) to the engine casing. If both my engines are as im told independant, a alternator and battery each why would one alternator wired any different from the other? Come to think of it they are different alternators so that maybe the reason (I will confirm the make of each as soon as i can). Also both starter/ignition lights are telling me that the both alternators are not charging (lights stay on). The lights actually have brown connected (and green) so i can only assume that the colour must change within the loom at some point. I now believe that the alternators should be 14v/60amp according to the volvo website, god only knows what Ive got ??? I will however check and re-post. Either way im pretty much convinced ive got to find two new replacements now.
This is wat i think they should be ?