Question
Alternator Pics 1
QUESTION: Let me start from the beginning so you will have all the facts.
I was first having alternator issues with it overcharging and overheating my battery to the point of boiling and probably close to exploding. I assumed it was the voltage regulator and ordered one. While waiting for it to arrive I thought that perhaps since it wouldn’t be that much more expensive to just swap out the entire alternator that might be my best bet. So I ordered an alternator and decided to forego just the voltage regulator replacement.
I found what I thought to be a somewhat competent local mechanic to do the simple take off, connect and bolt on job for me. So I let the fellow do it. I picked up the car from him after the first alternator was installed and the alternator light was on. He seemed to think it would reset itself if I drove a bit. I didn’t have anytime to have him check it further and it sounded like he wouldn’t check anyway so off I went on about a 60 mile each way trip on business. The light did go off enroute so I thought it had reset itself as he said. What probably happened was that it was warning me that the alternator wasn’t charging and when it quit charging completely the light went out since it had no more to say on the subject. I drove along clueless for the trip down and back.
I suppose my really strong battery is what carried the day because I was driving in rain with the headlamps, air, wipers, and radio all on. I actually made the entire trip and almost home before the wipers slowed to a crawl and the car died at the entrance to my neighborhood. Thanks to a quick jump from a neighbor I got it home safely.
I put it on a battery charger overnight to get enough power in the battery to get it over to the mechanics to have him pull the new/bad alternator so I could take it in for a free replacement. Here’s where the story gets interesting. I did not pay attention to the original when it came off. I simply used it as an exchange for the new one in the box which I didn’t take a close look at. I took it back to him and he said there was a problem. This replacement alternator wasn’t the same one as the one he just put on that went bad. I was not happy that the parts place gave me the wrong one and now I had to wait for another to arrive. In the meantime my friend who works at the parts place who gets me the parts at wholesale couldn’t believe this one was different. He took a look at the original that I traded in and lo and behold it was the same as the one I had just taken the mechanic to put on. It turns out the first replacement was the odd one and the mechanic didn’t catch it while doing the swap out. Of course I didn’t either since I was just dropping off the new part to him. The first replacement failed one had two post connections and two spade connections, one recessed and the other slightly elevated. Since there were only two wires and he obviously didn’t pay much attention to the connections otherwise he would have noticed the alternator didn’t match in the first place, he could very well have connected it wrong. If so, could that have caused the alternator to fail? I’ve noticed on schematics that I’ve found that it appears that it should have four wires go into the alternator but there are definitely only two wires available on my car. I’m not very technical so I could be reading the schematic wrong.
Now we are at the next replacement. Once we convince him that the replacement we have actually matches the first one he reluctantly puts it on believing he couldn’t have mistaken the first alternator for this one.
Prior to this I had it bench tested at the local parts shop but because it was for an older Jaguar their modern system had trouble testing it. I don’t know why they don’t just have a generic tester. An alternator is an alternator is an alternator. One would think. Regardless they couldn’t tell for sure if the new one was good or not so I had no choice but to roll the dice and put it on and see if it would work.
It appeared that all was well because after he is done putting it on the car the alternator shows it is putting out about 13.5 volts which is about right and away I go. No battery/ignition light on so I assume all is well. I get home and shut the car off and the battery/ignition light now stays lit. It won’t go off until I disconnect the negative battery cable in order to not drain the battery.
I fire it up the next morning and she starts fine since the battery wasn’t dead and I do as he says to check the alternator by removing the negative battery cable while it’s running and sure enough the car dies which he says is indicative of a bad alternator. I then take it to the local parts place where they hook up a diagnostic tool to it which shows the battery and starter are good but the alternator isn’t putting out any current at all. So the assumption now is that we have a bad alternator again. Is this possible? Could there actually be two bad alternators in a row that worked briefly but fizzled out within a few hours?
So that’s where I am now. The mechanic charged me a second time to do the new replacement since he hadn't supplied the part he said it wasn’t his fault which I suppose is correct providing he installed it right in the first place.
A little more information here as well. I haven’t had a working voltmeter gauge since acquiring the car a few months ago. The seller gave me spare gauges since the speedo, oil pressure, and voltmeter gauges weren’t working. The other two gauges we can discuss another time. Right now I’ll focus on the voltmeter because the mechanic seemed to think that if it wasn’t working it might be causing some of the alternator issues. I didn’t think that was so since the car worked fine the first few months without the gauges operating correctly. Nonetheless I took a crack at replacing the gauges only to find that the voltmeter gauge wasn’t hooked up at all. I’m sure that both connectors didn’t just work their way loose because they fit quite snugly. I am assuming that the PO left them unattached intentionally for some reason. I hooked up the existing gauge, hopefully correctly and nothing registered. I tried the two other replacements he gave me and still nothing. So I am baffled by this but still not sure if this would affect the alternator.
While I was tinkering with the gauges I discovered a couple of mysteries, to me at least. One was that the black wire that I assume goes onto the voltmeter has two choices. I have a wire that has two black wires coming into a single connector or just a single black wire. I’m not sure which to use and what to do with the leftover wire since all other gauges are connected and it doesn’t appear to be going anywhere else. Also there is a lone black wire with a pointy connector that I can’t figure out where goes. Again, none of this may be affecting the alternator but I want to get it connected anyway so I can monitor the battery charging in the future.
So I’ve attached a few photos here for you to see what all I’m talking about. I have a shot of the original alternator that came off the car and the first replacement one so you can see the differences and maybe can tell which is actually correct or if either can be used. I don’t have a photograph of the second replacement because it’s still on the car and besides it’s the same as the first one.
My friend at the parts store went ahead and ordered yet a third replacement if indeed this alternator is bad. He says it looks even different then the first two. Were there that many variants on the alternators for these cars? If so I’ll try to get a photo of this latest one in the mix and get your opinion on it. I don’t have that just yet though.
So I guess what I am asking is this. Is is possible that two alternators in a row failed? Is it possible the first one failed due to an incorrect connection or something else wrong with the electrics in the car that could have burned it up? Is it possible the second alternator could have been damaged by the attempt at bench testing it thus killing it before it was ever in the car? I doubt this since it appeared to be charging when I picked up the car the second time round. So it seems that either it truly is just bad luck getting two bad alternators in a row, the connections are correct thus making it appear that the alternator is bad, or that the alternators are being ruined by something in the electrical system.
So now kind sir I pass this mystery on to you and your expertise for a plausible answer. I am at my wits end and rapidly running out of money on this project. I can’t keep throwing alternators at the problem if it lies elsewhere. I would like to get to the bottom of things before I put yet another alternator in. I have limited electric experience and no meters of my own. So I’m hoping the answer might be something simple.
Any help you can offer is most appreciated. My apologies for rambling on and supplying so many photographs but I just want to make sure I’m not missing anything that might help you to help me.
Thanks!
Rick
PS: I just realized that I can only attach one image to this question. So the only photo is of the 2nd replacement alternator. I was hoping to show you a photograph of the 1st replacement alternator as well as photographs of the gauges and wires. Is there another way I can get these to you? Feel free to respond directly to me via email if you like.
ANSWER: Hi Rick,
Wow! you have had a series of problems. The series III XJ-6 Jaguar has a two wire alternator. One large post which is connected directly to the battery at all times. The other (small wire) is the (exciter or trigger wire) which is connected to the ignition switch through a idiot light with a resistor shunt around the idiot light for safety if the bulb burns out it will still excite the alternator and keep it charging. If you loose this "exciter or trigger" power the alternator will quit charging at low RPM and may or may not start charging when revved up. Some do and some don't.
Some bad news though. The test you mentioned about removing the power wire off of the alternator while it is running to see if the system is working or not was an old General Motors test. However, on many foreign alternators it instantly fries the alternator. Some re-builders have installed a safety Zenner diode to stop from destroying the alternator if the cable is removed or accidently gets disconnected.
Here is how the system operates and the proper way to test the car and the wiring and the alternator.
You need a 12v test light and a volt meter (both are very inexpensive) and you will need them to correct any and all other electrical problems including your instrument problems.
First set your volt meter on a scale that can read in the 12v DC range and check the battery voltage at the posts (not the cable ends)(should be 12v+)
Next turn on the head lights and wipers and any other electrical items you can and put the volt meter on a low volt scale (0 to 1 or what ever is your meter's low volt DC range) Put the positive test lead on the head of the engine and the negative test lead on the negative POST (not the cable end) of the battery. If you read .5v or more you need to correct the negative cables (post to cable, cable to body, engine ground strap) This is called a "Voltage Drop test of a cable system". Now keep the connection as is and hit the starter and watch the voltmeter.
Next, connect the positive test lead to the positive POST of the battery and the negative test lead to the large POST on the alternator. Start the engine and if you get a negative reading reverse the test leads and read the voltage on the cable itself. Again you do not want to see more then .5v. This is a "Drop test of the power wire to the alternator"
Shut the engine off and set your meter back to read 12v scale. Put the positive test lead to the positive POST of the battery and the negative test lead to the negative POST of the battery and read battery voltage. (should be 12v +) leave it on the posts and have someone start the engine and set the idle up a little and read battery voltage. It should read from 13.8v to 14.5v. This is a test of the out put of the alternator.
If you have two large posts on your alternator look carefully at any markings near the two posts. One will have a (+) and the other may have a (-). If that is true you connect the power large wire to the (+) and add a ground wire to the (-) if there is not ground wire in the area.
Another test of the diodes in the alternator. ENGINE OFF and remove the large (+) power wire from the alternator and confirm that the wire is 12v+ and then take your 12v test light and connect the clip to the post on the alternator and put the pointed probe on the wire end. The test light MUST NOT light up.
Next, connect the hot wire back on to the alternator and remove the small spade connector wire from the alternator and turn "ON" the ignition (not to "Start") Note if the idiot "IGN" light is on or off. It should be off. Now with the ignition still in the "ON" position touch the end of the spade to a ground while someone watches the Idiot light. It should light up. Remove it from the ground and it should turn "OFF". Then plug it into the spade terminal on the alternator and it should turn back "ON".
That is a test of the wiring and idiot light system and a preliminary test of the alternator.
I know the wiring diagrams are difficult to read for some circuits, so let me know what circuit you need to test next for the instruments that don't work and I will post one on my web site for you to copy. One at a time though.
Howard
---------- FOLLOW-UP ----------
QUESTION: Hello Howard,
Thanks for the quick reply. I have a couple of follow up questions for now and perhaps a couple more about the gauges once I get the alternator situation sorted.
First of all I will try to pick up the meter and test light tomorrow as you suggested to do the tests you recommend. I'm not sure how easy it will be to do these tests since as you know the location of the alternator isn't an easy one to get to and I suppose I will be doing the tests more from touch than sight.
I do have a question though because I got some information from an Jag forum I also checked with and the fellow on there seems to think the small brown/black wire for the idiot light is incorrectly connected. He says the spade connector is for a radio suppressor and the wire should be going to the small post. How could the previous alternator that was in the car when I got it have been operating properly until it failed if it should have been connected in that fashion rather the way it was connected via a spade connector? He said that fluctuations in this bad connection could have damaged the alternator. So should I take the spade female off the end of the wire and replace it with a round connector to put it on the small post? Just trying to get things connected right to start with prior to starting my tests.
So what are your thoughts on this and how should I proceed?
Thanks!
Rick
AnswerYou need to see what the terminals are labeled. If the large post is labeled (+) or (B+) you put the power wire on it and If the other bolt on terminal is labeled (-) you need to put a ground on it and if the flat spade terminal is labeled (D+) you connect the idiot light to it. Some alternators label the idiot light terminal as "Lt" (light).
However, if the the large post is (B+) put the battery wire on it. If the other post is labeled (D+) then that is where the idiot light wire goes.
You may need to jack the car up and use a light and a small mirror to see the terminals or remove the alternator and look at the labeling since you have a aftermarket alternator.
Do not experiment by connecting wires to see what happens. In the box the alternator came in sometimes they include a card or sheet telling the connections.
Do test the wiring in the car that way I explained above. The cars were all wired the same.
Howard
