Alternator/charging circuit

[flounderbout]

Have a shiny new alternator here, but just want to check that the chraging cicuit is all good before I get into the nightmare of working out how to get swapping it in sorted.
I'm getting no battery charge light on ignition or engine running, but know the bulb works because I have swapped in another dash fron the red truck (and swapped bulbs around).
Yellow wire going into dash/battery light shows no voltage on ignition or engine running.
Middle wire from three wire plug on back of alternator shows 12V on ignition and engine running - brown wire shows no voltage on ignition or engine running (well actually shows slight reading on engine running (0.3V).
But getting no charge at battery when engine running.
Does this mean circuit is good but alternator screwed?
Or is there anything else I can do to check the rest of the circuit? Circuit diagram shows some fuses that are meant to be left hand side of steering column, but can't for the life of me find them!
Many thanks if anyone can help out.

[gary-r]

test the ign lamp wire by earthing the connection at the alternator - its the right hand wire on the plug looking at the back of the alternator with it earthed turn on the ign switch - if the wire is good the bulb will light. pull the plug to do this and use a paperclip or something small to probe the plug

if that circuit tests ok and you have 12v on the middle wire it looks like the alternator has died

i have a picture but the attachment thingy is temporarily broken - ill post it later for you

[gary-r]

theres the pic showing the wee plug - have you checked the 7.5a fuse in the fusebox under the bonnet

[gary-r]

oops speed reading - if you have 12v on the middle pin the fuse is good.

an alternator wont work if the ign lamp circuit is broken - its the trigger for the regulator

[flounderbout]

Sorry probably being stupid. Do I need to earth the RH wire while the plug is connected? Have tried that and bulb won't light.

[gary-r]

no pull the plug and earth the pin - all your basically doing is lighting a lamp using a + and -

with the ign on it feeds 12v to the lamp and you are earthing it to complete the circuit.

if it doesn't light up and the bulb is good check its getting 12v to the bulb.


you can jerry rig it to work to check the alternator with a small sidelight bulb. connect the + on the bulb to the + on the battery and link the - on the bulb to the right hand pin. turn on the ign and you will have an ign lamp. if it goes out when started you have a fault in the ign lamp circuit. if it does go out check for 14v at the batterys - that will confirm the alt is ok

alternators are fairly simple things but this lamp must work to trigger it.

[flounderbout]

So I have finally got somewhere, though not sure where!
The reason I couldn't get the charge bulb to work is because it doesn't appear to be wired into the charge circuit!
This all started when the engine went into limp mode while driving and the ATF TEMP light came on. I figured this was another transmission problem, but as Vince points out the ATF TEMP bulb is no longer a fault bulb for the Lexurf... To cut a long story short I took the bulb out of the AFT TEMP socket and all was well again. Anyway today I swapped in another gauge set again and earthed the charge lamp circuit - hey presto, the AFT TEMP light came on! So it would appear the charge circuit is running through that rather than the battery light.
So I'm wondering if the warning I got originally was an alternator failure... Anything else I could check before I bite the bullet and get the alt swapped out?
Also, how the f*&£ty f&*k do you get the alternator out? Is there any way of manouvering it down and backwards, or is does it have to come out forwards (which looks to me to be a complete nightmare!!!)? Is this a job to leave to a grown-up?
Any help greatly appreciated.
H

[gary-r]

try doing the jerry rig way i said in the last post - it checks the alt circuit and the alt in a simple test.
snip the right hand wire and connect the small lamp to the plug (easy to solder back together later) you can test the whole lot that way without removing the dash.

the alt only comes out from the front due to the mounting bolts being on the front. you cant even see them until the rad is out.

[flounderbout]

Brilliant thanks Gary, and apologies for not following through your previous post properly. Will give it a try shortly.

[gary-r]

these might help if you need to take the alt out - lets you see where the mounting bolts hide.

its a fairly easy job once the bumpers off, the grilles out, the fans out and the rads out

[flounderbout]

So I have soldered up a little test bulb (and yes the bulb works!). When I attach to batt and rh wire of alt plug I get nothing with ignition on or off or engine running?

[gary-r]

mmmm - if the middle pin on the plug is getting 12v it looks like you have a dead alt.

you can run a wire from the batt + to the middle pin and leave the small lamp linked as a sure test. if you still have no lamp it looks like your alt has died henry.

usually a dead alt has a permanent warning lamp but mine had no lamp at all when it died.

[flounderbout]

mmmm - if the middle pin on the plug is getting 12v it looks like you have a dead alt.

you can run a wire from the batt + to the middle pin and leave the small lamp linked as a sure test. if you still have no lamp it looks like your alt has died henry.

usually a dead alt has a permanent warning lamp but mine had no lamp at all when it died.

I fear you are right. Wishful thinking has kept me tinkering til now! Many thanks for your help though. Much appreciated. I fear I will have to turn it over to a grownup now. Hope TonyN is rested when he gets back from his hols!