Alternator?

Hi all!

Had to change the alternator recently as it was sending the battery 18v+ at idle. Also made the abs and battery light remain on. I put in a new battery too as it boiled the other one.
Got that all done and the voltage at idle is 14.4v. But if reved slowly it remains at 14.5 ish but if revved quickly it's like the regulator can't keep up.. increases to 14.8v then back to 14.4 ish.
I now have a very dim battery light on which seems to change in relation to the revs. Checked belt and alt connections all OK.
Anyone had this before?? I do have a single green blue wire with a crimp attached just not connected.. seems to come out of the same part of the loom but I imagine this is from the air con I removed ages ago..

Thanks

14.4v is a good charge .... battery relocated .... have you checked the earths ... you can always use a jump lead to earth off things like engine to body alternater to body etc see if that helps ...

You checked the wires into the big plug on alt and you put the wire on with the 8mm nut and it ain't shorting ?

I haven't relocated the battery. I did check the connections but will confirm again to be sure.. I'll check the loom and gnd resistance tomorrow too. Could the 75amp alt fuse cause this?

Since having the alt replaced I think the dim battery light only comes on after the alt has been charging for while as I just started it and run it for 5mins and no dim light. Will have a proper look tomorrow and let you know.

Sorry I mean the big plug on the alt ain't they the ones that put battery light on ?

I would say it's your bottom pulley that is fucked.
Check to see if the metal rim has seperated.

I was getting to that stu ....hopefully its just a loose plug or something ....

Thanks for the hints guys.

I've just checked everything and there is continuity between alt plugs, sense line, battery, gnd's and no shorts etc so that seems fine. Let it idle for about 30mins and the voltage was starting to drop off to 14.1v which I'd expect if the battery's nearing full?
The dim batt light is happening when I turn other loads on, so light's, rad fan's, stereo and controllers etc

I've looked at the pulley and seems to spin true and the alt pulley looks constant. Aside from taking the thing off Ive only tried to rock each side like checking for wheel bearing failureally and its solid.
Could it be that blue print have supplied me an under rated alternator? Like 60a instead of 80a?

Any ideas?

What the alternator voltage when under load with headlights rear demister on for example .
Either voltage regulator faulty or wiring resistance issue. Clean cable contacts with electric contact cleaner and recheck voltage drops  etc .
What blueprint part number did they apply you with ?
Should be adn11134 rated at 80A

With everything off was 14.2v then with those two on 14.1v.
I have tested everything crimp to crimp too and showed 0.2ohm- same as when the test leads are shorted so didn't seem like it had any added cable resistance..

That is the part number on the bill and the new unit but had oil filters from them with the wrong threads in the past..

^ Ideally you want do a voltage drop test, continuity meter test won't pick up high load resistance (could have a big cable with most strands broken or rotted & it still read a multimeter continuity resistance of 0.2ohm range)
I suspect corroded or bad joint somewhere creating enough potential difference between alt & battery that makes light glow lightly .
Clean everything with elec contact cleaner & if got suspect cable try a temp bypass test with jump lead or similar.
link below with basic points on voltage drop testing
https://www.engine-light-help.com/voltage-drop.html

What about the battery lead do yo have the red or black connector just away from the battery sure Stu had a problem there or suggested it to a member who had charging issues

^ fusible links, they can be troublesome when old & corroding .

I still dont see how at 14.1 v its throwing the light on even if its dim surely it must be a wiring issue ...

If the diode pack in the new alternator is dodgy then might be getting a bit of AC (or spikes) out of it.
Was it new or re-conditioned?

It sounds likely wiring but if unlucky could be alternator fault .
If get nowhere with wiring you may want see if can swap to another alternator, blueprint bloody expensive too so be sure it A1

nomad wrote:14.4v is a good  charge .... battery relocated .... have you checked the earths ...  you can always use a jump lead  to earth  off things like engine to body alternater to body etc  see if that helps ...

Great advice mate.

I have just re earthed my battery in the boot to the top of the spare wheel fixing hole.
I had it bolted to the boot floor but it kept coming loose.

I seen the wires look ok but near the plug be corroded. If you unplug alt plug dose the light fully go out or come on ?

Thanks stu .... used that method many times its just handy as a temporary earth as you can normally see the meter go up on the if there is an earthing issue ....

Thanks for the help guys, got home started it and the battery light is dimly lit even without any extra load and clears if I increase the revs.

Volt drop test with everything but rear demist on was 12.6v off, 14.23v charging voltage, 0.2v drop positive, 0.34v drop negative.

Starting to think it's the wire going from the alt to the bulb only I can't get my probes in the back of the plug to see what it's sending and no pins to stick in it.
Tempted to send the alt back anyway just to rule it out.

I also drew a line across the pulley and took it up the road for ten mins and the line was in the same position. Is this enough to tell me it hasnt seperated?

To conclude this topic.. Got another alternator and problem sorted.

Did Blueprint dealer swap that over no problem ?

Yes, blueprint come with 2yr warranty anyway