Problems with charging

[sam2.0 10]

I've bypassed the earth by taking the negative to the body of the alternator.

 

I've also taken reading from the output on the alt to the earth and its the same. Its not a cable/connection issue, it seems as something is draining charge.

 

I also took each fuse out one by one and the output didn't change.

[quicky1980 0]

dodgy alarm?

[sam2.0 10]

I'd love to know how to disable it!

 

My alarm key looks like a scorpion alarm sa30 fob, but can't find a manual.

 

I suppose, as its an alarm I need to get to the main box and disconnect it?

Edited March 23, 2012 by sam2.0

[dannyboy 0]

Do u have subs in the booth?or an amp?

[sam2.0 10]

Used to, cabled still in boot.

[hrdwdpro 10]

I have not read all of the responses to this thread as I am searching for answers to my personal issues but it sounds as if the exciter wire is not doing its job. The alternator does not begin charging until the battery light comes on. If it does not work properly the alternator will not begin to charge. Sometimes they will self excite but that is not the way they are designed it is a fluke if they do. My alternator did self excite but only a single wire alternator is designed to do so. My engine is a swap into a mk1 and the hack that built the car was a wiring infant. I had to install an exciter wire that did not run through the instrument cluster. I can not recall exactly what my solution was but i know i installed a 12v power wire and attached it to the blue exciter wire to get the alternator to excite. My suspicion was correct when the engine was running but the alternator was not charging. as soon as I applied 12v to the blue wire the alternator began to charge. when testing a three wire alternator you will run 12v to the exciter by default and the alternator will test to be good. when you install the alternator in your car it will not function properly. I ran a 12v power supply to my alternator exciter wire with a diode inline. My problems were solved. I hope this helped or maybe its rubbish in which case feel free to hammer me.

[sam2.0 10]

Interesting. I was sure the light on meant it was not charging...

 

Anyway, I get voltage between the blue cable (tickle as you're calling it) and the fuse box, so its getting something.

 

Worth wiring up a 12v battery to it?! to ensure its getting charge?

[hrdwdpro 10]

Interesting. I was sure the light on meant it was not charging...

 

Anyway, I get voltage between the blue cable (tickle as you're calling it) and the fuse box, so its getting something.

 

Worth wiring up a 12v battery to it?! to ensure its getting charge?

 

the battery light should come on then turn off if the light stays on you have a problem. but a known good alternator installed can only be limited by three things because it is a three wire alternator. the blue exciter wire is typically the culprut. bypass the cluster and fuse box and jump 12v to the blue wire while it is running. use your multimeter on the post sticking out of the starter and the post sticking out of the alternator. you should see 13-14v at the alternator post then check the starter post you should see.the same there. continue down the line of possibilities. there is always the grounds but with a car that old eliminating the factory wiring for the exciter will help to determine if the problem.is in your fuse box or cluster.

[hrdwdpro 10]

Interesting. I was sure the light on meant it was not charging...

 

Anyway, I get voltage between the blue cable (tickle as you're calling it) and the fuse box, so its getting something.

 

Worth wiring up a 12v battery to it?! to ensure its getting charge?

 

The light staying on does mean that it is not charging. The light should come on and then go out. But if you run 12v constant to the terminal on the alternator that the blue wire connects to while the car is running you will either see 12 volts coming out of the alternator or not. The trick to simplifying the diagnosis of the alternator is to isolate it from your fuse box and cluster. There are too many variables with an old car to do anything else. You run 12v constant to the exciter input terminal on the alternator. Just go straight to the alternator and hook it up at the stud. Take your multimeter and check for 13-14v output on the large stud if you see good voltage the alternator is working. Then check for the same voltage at the starter post. If you see good voltage there the cable is good to the starter. then check for the same voltage at the battery. again if you see good voltage there that length of cable is good and you are charging the battery. That is a simple way to test the system and eliminate the question marks of bad fuse box or cluster circuitry. Now you can either run a 12v power source with a diode to your alternator and eliminate the factory circuits, or you can install a diode which is a very cheap item, leave it hooked up this way while you find you short in the circuitry, and then hook the blue wire back up. Either way if the tests work out for you your car will be back on line until you finish the job. I personally just eliminated the factory circuit. The only thing is do not hook up to any ignition power sources or your car may not shut off when you turn the key off.

[sam2.0 10]

The light staying on does mean that it is not charging. The light should come on and then go out. But if you run 12v constant to the terminal on the alternator that the blue wire connects to while the car is running you will either see 12 volts coming out of the alternator or not. The trick to simplifying the diagnosis of the alternator is to isolate it from your fuse box and cluster. There are too many variables with an old car to do anything else. You run 12v constant to the exciter input terminal on the alternator. Just go straight to the alternator and hook it up at the stud. Take your multimeter and check for 13-14v output on the large stud if you see good voltage the alternator is working. Then check for the same voltage at the starter post. If you see good voltage there the cable is good to the starter. then check for the same voltage at the battery. again if you see good voltage there that length of cable is good and you are charging the battery. That is a simple way to test the system and eliminate the question marks of bad fuse box or cluster circuitry. Now you can either run a 12v power source with a diode to your alternator and eliminate the factory circuits, or you can install a diode which is a very cheap item, leave it hooked up this way while you find you short in the circuitry, and then hook the blue wire back up. Either way if the tests work out for you your car will be back on line until you finish the job. I personally just eliminated the factory circuit. The only thing is do not hook up to any ignition power sources or your car may not shut off when you turn the key off.

So to build a cable up, so I can get the car places, what diode and fuse would I use?

 

A guy at work doesnt see why we'd need a diode...

 

ETA: What fuse does it use in the fuse box, fuse number? I havn't replaced them all, it might be a simple replace the fuse job.

Edited March 27, 2012 by sam2.0

[hrdwdpro 10]

the diode is a one way valve to ensure that with the car off you do not end up with 12v backfeed and a battery drain issue. the part number from radio shack is #276-1661

[sam2.0 10]

So thats 6amps, I'll fix a 5amp fuse to the cable as well, just to be safe.

 

Thanks for all of your help! I'm finally driving it again.

[quicky1980 0]

so sounds like it was the blue exciter wire/cirevuit at fault? wow, what a pain youve been through to resolve the issue!

[sam2.0 10]

Indeed it does.

 

Don't want the alternator back do you?

[destructiv dave 0]

Hi Sam - glad you've got it sorted. Had a feeling it would be to do with the exciter wire, but didn't have the skills to resolve it!

[sam2.0 10]

No one I talked to knew about the excite wire, next time I'll be on the ball!

 

I literally tried every reading apart from the excite wire, even if I did, I'd not know I needed a reading.

[fla 9]

where does the exciter wire go from physically ie what is the route and where should the connectors en route be? I've got the same issue with the alternator not charging the battery :(

[sam2.0 10]

It goes through to the fuse box in the drivers foot well.

 

To prove that its the excite cable, just put 12v from the battery to the excite terminal on the alternator and test the current across the battery.

[fla 9]

Thanks Sam. So i connect the 12v positive cable to the exciter wire on the alt and then put a voltmeter across the battery (in parallel) or an ammeter (in series) with the battery?

Mine was an auto before and the blue wire ran acros the front of the car to a connector to the other side (in a black sheath with white tracer, with the crank sensor wire iirc). Not sure where it went after that though...

[sam2.0 10]

Sorry, voltmeter. You should get ~14.4v across the battery. Try it before and after adding the 12v to the excite terminal, so you can see a difference.

 

Mine is more like 13.8v now it's all fixed. Reckon if I replaced to return (from alternator to Batt) it'd be better.

[fla 9]

Ok very strange here - ignition on engine off 12.65V engine on 14.4V so it suggests that the alt is doing its job. Why thenh was it not charging in the rain? I dont think the rear demist, fans and radio would drain the battery faster than driving it could charge? Unless the excite wire is loose somewhere causing intermittent charging?

[dr_mat 0]

I have a dodgy regulator on my alternator - it doesn't start charging until the engine revs over 2k on startup. There's all kinds of weird ways these electrical circuits can fail ...

[sam2.0 10]

A short perhaps? Get a reading with the car on, and start turning electrics on 1 at a time. You'll get an idea of what is causing the issue.

 

I initially assumed my alt just wasn't outputting enough, as the car would only fail when it was raining in the dark with my requirement for some loud music. I figured having the wipers on full, full beams and the stereo loud was just taking too much drain. When I say fail I mean the engine just died.

[fla 9]

should the voltage drop as things are turned on? Wouldnt the alternator compensate accordingly? I'll try that later today - yours is a similar scenario to mine - rain, HU on, headlights and apparently strong battery drain. I also noticed it when i turned the engine off in traffic. When i came to start it again it struggled slightly to turn over as if the battery was draining. We only had the HU on at that time - maybe thats the issue?

[sam2.0 10]

It does drop slightly, well for me it does.

 

HU (head unit?). Seems possible, but if you had the ignition on (engine off) it could be a few different things. Try with the key out and turn the radio on, see what the drain is.