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Post by 1800heap on May 14, 2020 2:07:51 GMT
Just tested my email alternator with a 21 watt indicator bulb in series with the test wire as David suggested and it worked just as well. As David said it does not drive the alternator as hard as possible so was a safer test. I also had another read of the Australian manual and their method is also a test for full charging current capacity of the alternator so we dont need to do that.
David would you suggest I edit the post?
Nick
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Post by 1800heap on May 14, 2020 2:44:10 GMT
This is the amendment to the test lead that David suggested for some added safety.  Nick |
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Post by dave1800 on May 14, 2020 7:15:21 GMT
Thanks Nick, a picture is worth many words! Another thought, if there was some sort of a short in the alternator field coils then jumping to the battery without some form of resistance in the lead such as the bulb could result in a big spark and maybe nasty skin burns.
Maybe worth a quick edit to your earlier post when you have the opportunity.
David
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Post by paddymk2 on May 14, 2020 11:35:22 GMT
Thanks for all that instructions and safety advice.
Stop and think through is what i’m hearing.
And that means tidy the garage and make a bit more safe space.
ill keep you updated.
ill have to gather a few bits for Saturday morning.
The alternator ground (casing) was good, by the way.
i was also wondering if there was possibly a leaky connection through some other component. like if i turned on the ignition key but didn’t start the car? like that solenoid switch? (a couple of times last year, when i turned the key, there was nothing, not a click or any lights, and a wiggle at that unit brought on the lights and then the car started.
thanks anyway.
paddy
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Post by 1800heap on May 14, 2020 21:09:47 GMT
Thanks Nick, a picture is worth many words! Another thought, if there was some sort of a short in the alternator field coils then jumping to the battery without some form of resistance in the lead such as the bulb could result in a big spark and maybe nasty skin burns. Maybe worth a quick edit to your earlier post when you have the opportunity. David Yes I agree I will fix the post thanks David |
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Post by 1800heap on May 14, 2020 21:24:41 GMT
Thanks for all that instructions and safety advice. Stop and think through is what i’m hearing. And that means tidy the garage and make a bit more safe space. ill keep you updated. ill have to gather a few bits for Saturday morning. The alternator ground (casing) was good, by the way. i was also wondering if there was possibly a leaky connection through some other component. like if i turned on the ignition key but didn’t start the car? like that solenoid switch? (a couple of times last year, when i turned the key, there was nothing, not a click or any lights, and a wiggle at that unit brought on the lights and then the car started. thanks anyway. paddy We usually assume because the ignition light comes on that the circuit is ok but you are right there is some potential for the light to come on with a ground loop. You can check this by pulling off the left side spade connector from the control box. With the ignition on and engine off this should make the ignition light go off. You can also check the voltage on the right hand screw terminal which should be around 1 volt with engine off and ign on. Depending on battery voltage might be slightly less. It should go up to 2 volts ish when you unplug the field/aux wire from the alternator. Unplugging the alternator only will not turn off the ignition light. Nick |
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Post by dave1800 on May 15, 2020 11:36:06 GMT
Paddy
I assume you have checked the earth strap from the engine block to the body; bad earth contacts usually show up as problems with the starter not working or intermittent. I assume the bolts holding the alternator are making a good ground to the engine; clutching at straws but quick easy checks!
David
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Post by paddymk2 on May 16, 2020 6:45:48 GMT
Hi Dave
Yes I did check the continuity from the alternator casing to the battery.
And from the b-post to the battery
I had initially assumed it would be just a loose connection (and may still be)
So Nick
I did the test with the lamp (rear light)
I charged the battery before the tests - and was reading 12.9V before starting the car.
I started the car once before the test - just to make sure it would start when doing the test.
My helper ("her-in-doors") started the car
Initially the voltage fell to 12.6V
When I touched the cable to the positive the voltage didn't seem to move. It didn't go down to 12.3 or up to 14V(?)
I noticed there was glow on the lamp filament - not bright but something
So I don't know why the bulb would light if there was no voltage?
I only had a few minutes before the boss had to leave - but my son should swing by this evening - so I could have another go (I had the multimeter probes clipped onto the battery so may want another go.)
Regards
Paddy
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Post by dave1800 on May 16, 2020 10:49:48 GMT
Hi Paddy
I think Nick was trying to get you to check the output of the alternator just by itself and not the combination of alternator and voltage regulator so you know which way to go.
When you use the jumper from the alternator field coil to the battery positive terminal using the light bulb in series it should be the brake light filament 21 W not the rear light part 5W - as the latter possibly won't pass enough current to get an output.
If you can measure the voltage directly at the alternator between ground and the thick wire ie the main alternator output connector that would eliminate any issues down the line. I think you may have been checking across the battery, not sure from your post, and if so then this could be misleading if there is an issue with the wiring or the voltage regulator.
Good luck!
David
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Post by paddymk2 on May 16, 2020 12:00:23 GMT
Thanks Dave
I did use a bulb from a rear indicator bulb - that should be 21W (but its an old bulb & holder with dual filament so maybe its not right.)
You mean, check the voltage output at the alternator in case there is some drop across the starter solenoid?
I'll have another go.
Paddy
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Post by 1800heap on May 16, 2020 22:38:07 GMT
Thanks Dave I did use a bulb from a rear indicator bulb - that should be 21W (but its an old bulb & holder with dual filament so maybe its not right.) You mean, check the voltage output at the alternator in case there is some drop across the starter solenoid? I'll have another go. Paddy Hi Paddy You will need to make sure you are using an indicator bulb 21 watt type rather than the dual filament type as any lower wattage like 5 watts won't energise the field coils enough. Testing the voltage at the battery should test the complete output circuit but as David said there still may be an issue with this even though you tested it for continuity before. A voltage rise at the battery is a pass, anything else is an issue because no charging is happening! This test does not test the exciter doides or the regulator. If you have a glow on your bulb it would suggest the field coils are ok. You will not detect a voltage rise on DC volts if the alternator is putting out AC and has faulty doides. You can also check for AC voltage to see if this is the case. Nick |
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Post by 1800heap on May 16, 2020 22:59:32 GMT
I should have said, no voltage rise at the battery suggests a bad connecton from alternator output to battery, (this really would be the section of cable between the alternator and the starter soleniod as the car starts so it won't be the battery cable) or it is an alternator fault.
Nick
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Post by paddymk2 on May 17, 2020 7:09:43 GMT
Just got back from Autobarn with a 21W bulb and tried that.
With the ignition on and the field and aux connector removed and replaced with the test wire with 21W bulb
The initial voltage was 12.8V with nothing on - this fell to 12.5V at the ignition on but engine not started (it drifted a little lower)
With engine running I was at 12.60V
When I tapped the other side of the test wire to the positive battery terminal I got 12.69 to 12.75V
This was reproducible in that there was an increase in voltage of 0,1 to 0,15V
And the bulb filament did glow.
I was alone - so I couldn't see what the charge indicator lamp was doing.
A couple of other points
(a) The lamp has come on a few times when I've been starting the car - its previously always gone out after a bit of revs.
(b) Occasionally I find it hard to restart this car - I'd always put that down to some kind of vapour lock (as per other discussions)
(c) The engine has not been tuned - but the engine was out with repair to the gear box - not much was altered other than the cables (choke, kick down etc.)
(d) In the manual it talks about bringing the revs up to 1700 or higher - I'm not doing anything like that for these tests.
Regards
Paddy
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Post by 1800heap on May 17, 2020 7:22:27 GMT
Hi Paddy
Thats not enough of an increase for the alternator to be charging propery. I would expect at least 2 volts rise. Did you try your meter set to AC volts? If you are getting the test bulb glowing the field coils are working. Was your trouble starting because the engine was turning over with the starter a bit slow? Perhaps the alternator has not been charging properly for a while!
Nick
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Post by 1800heap on May 17, 2020 8:25:05 GMT
As a reference this is my bulb when connected to the field coil and positive. The camera has made it look slightly brighter than it is but there is no mistaking its on. I went from 12.9 Volts to almost 15 volts at the battery on my test but it will depend a bit on the engine revs and I tested it on the bench. I have just tested the field coil resistance on my good unit and I get 8 ohms ish with battery disconnected. It is looking like you have a faulty alternator although like I said it could still be the cable from alternator to starter solenoid.  Connected straght to the battery no alternator for comparison  Its a bit subjective but should give you some idea of the brightness of the test lamp. Nick |
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