Alternator not charging but alternator has been tested

[finch wxm]

I bought a used alternator set up with cup mounts butvi think the guy said it wasnt a cup alternator but was the same , possibly a ph1 diesel ?

Any ideas people ? I can get some pics and see if i can get the part number , it is a valeo unit.

Just going to collect it from the place its been tested

 

[dann2707]

Could be a bad earth not allowing it to charge. What voltage do you get coming out of the alternator when it's running?

 

[NorthloopCup]

Does the battery warning light on the dash work? Sounds daft, but sometimes they rely on that lamp to work.

 

[finch wxm]

Battery light is not on , im getting same voltage when running. I put the multimeter on the positive side of the alternator positive and im getting nothing there so thinking there is a break in that wire.

If i pull thr neg of the battery car dies

 

[finch wxm]

Does the battery warning light on the dash work? Sounds daft, but sometimes they rely on that lamp to work.

Yeah im wondering if its something daft , the looms are from my iceberg car but only change is the looms have been fitted to my new shell and the alternator set up has the cup mounting but is 110A valeo unit so not sure if because this is not an actual cup one does it need additional wiring to it to charge

 

[NorthloopCup]

Yeah im wondering if its something daft , the looms are from my iceberg car but only change is the looms have been fitted to my new shell and the alternator set up has the cup mounting but is 110A valeo unit so not sure if because this is not an actual cup one does it need additional wiring to it to charge

It will need a ‘signal’ of sorts to tell it to charge mate.

 

[JamesBryan]

Is the exciter wire plugged in?

As Northloop says it needs something to tell it to charge.

 

[Robbie Corbett]

I believe (although my memory could be well off) that the exciter wire is blue - sounds like its either not plugged in or is broken?

 

[NorthloopCup]

Just hot wire a 12v feed to the exciter on the alternator and see if it starts charging when the engine is running. That’s pretty much all that wire does anyway.

Confirms the fault and gives you a direct place to start fault finding.

 

[Tommyd1]

I've had issues with alternator also, very first night after buying my car everything went to sht, had to get a jump and brought car bk, they apparently got it reconditioned which took a full week, new battery included but when on long journey warning ping's low battery, I bought new battery just to be sure but only doing small miles during the week, when car's idling lights are kinda diming with the tick over, I'm kinda dredding the thought of having to take a long distance run incase the dredded ping sounds again! When it happens if you turn off the car and start again it's ok 🤔 thinking of just buying a new one but not cheap!!

 

[finch wxm]

Just hot wire a 12v feed to the exciter on the alternator and see if it starts charging when the engine is running. That’s pretty much all that wire does anyway.

Confirms the fault and gives you a direct place to start fault finding.

Will try this the exciter wire did used to be solder directly from the loom to it , its the same loom ive transferred to my new shell. Hooefully its something simple as ive been told the alternator is good.

 

[finch wxm]

Just hot wire a 12v feed to the exciter on the alternator and see if it starts charging when the engine is running. That’s pretty much all that wire does anyway.

Confirms the fault and gives you a direct place to start fault finding.

Ive just been looking at this , im not getting the battery light prior to starting on the dash 🤔 , tried direct 12v to the pin terminal on alternator aswell

 

[finch wxm]

Swapped the alternator aswell just to see if any change.

The spade connector do anything (w)? Never used it

 

[NorthloopCup]

Ive just been looking at this , im not getting the battery light prior to starting on the dash 🤔 , tried direct 12v to the pin terminal on alternator aswell

You need to start checking through all the loom connections for potential areas of concern then mate

 

[finch wxm]

You need to start checking through all the loom connections for potential areas of concern then mate

Bad times 🥲🥲🥲🥲

 

[finch wxm]

So i have 12v at the alternator casing when measured from the battery negative cable 🤔

 

[dann2707]

So i have 12v at the alternator casing when measured from the battery negative cable 🤔

That sounds like when an alternator fails and keeps killing the battery as essentially its shorting through the diodes. Either that or you have a positive cable touching an earth somewhere.

 

[Robbie Corbett]

The alternator also grounds through its case to the engine block - if somehow it couldn't (powder coatings, paint, corrosion) you might see some weird things like this.

I thought this was a new alternator? Have you had two do this?

When my alternator died it was the diode pack so the alternator was just shorted right across the battery which was.... quite smokey.... So even though you've swapped the alternator, this diode issue seems to be pretty common, ie, your new alternator could have the same fault as your last.

 

[finch wxm]

The alternator also grounds through its case to the engine block - if somehow it couldn't (powder coatings, paint, corrosion) you might see some weird things like this.

I thought this was a new alternator? Have you had two do this?

When my alternator died it was the diode pack so the alternator was just shorted right across the battery which was.... quite smokey.... So even though you've swapped the alternator, this diode issue seems to be pretty common, ie, your new alternator could have the same fault as your last.

Rob , the alternator is not a new one i have 2 x second hand ones i bought from forum members with cup brackets. The white car starts but i only get 12.6 v at battery while running. Ive checked the output at alternator and dont get anything , also noticed i dont get the battery light illumination on pre ignition and when i tested between battery negative and casing i was getting 12v.

The brackets are powder coated for the mounts.

I took the alternator to be checked off the car and told me they were ok. One alternator was worn but operational he said so that why i was convinced of a wiring error not causing the alternator to start charging.

Ive checked from the exciter wire cable to the white plug of death for a break in wire and all appears ok. But need to check from there into the car then , any ideas or anyone have a diagram where it goes next to test ?

I didnt want to just buy a brand new alternator unless i was 100% sure but i know if i did i would be 100% thats it is a wiring issue.

Ive removed the regulators from both alternators just now , one set looks like brushes are near end of life and the ones on the other look quite new so i could have 2 bad alternators.

I will test the diodes individually to see what i get , i know its going to take time to figure out.

My positive lug also just snapped to the alternator , i think im going to fit a fresh cable.

 

[finch wxm]

That sounds like when an alternator fails and keeps killing the battery as essentially its shorting through the diodes. Either that or you have a positive cable touching an earth somewhere.

Yes i need to check all the cabling as i wasnt expecting a voltage at the casing from the negative of battery which got me thinking is the diode pack shorting unless as you say a positive is touching which would be odd but could be possible.

 

[Robbie Corbett]

Can you check resistance between alternator body and block, I suspect the powder coat might be insulating the alternator mounts so they are not grounding to the engine block. There is no earth wire or strap between alternator and block (or batt neg) so the current return path is though the mounts.

If this is the case, I would not be surprised to find the alternator case measured at 12V relative to battery neg.

EDIT* Seeing as you have tried two alternators, and had them tested I am convinced the powder coat is your issue here, you can confirm that by connecting the alternator case to the batter negative terminal with a jump lead. But I would start by measuring resistance between alternator case and engine block.

 

[finch wxm]

Can you check resistance between alternator body and block, I suspect the powder coat might be insulating the alternator mounts so they are not grounding to the engine block. There is no earth wire or strap between alternator and block (or batt neg) so the current return path is though the mounts.

If this is the case, I would not be surprised to find the alternator case measured at 12V relative to battery neg.

EDIT* Seeing as you have tried two alternators, and had them tested I am convinced the powder coat is your issue here, you can confirm that by connecting the alternator case to the batter negative terminal with a jump lead. But I would start by measuring resistance between alternator case and engine block.

Yes i will take a look at this as both alternators were giving same symptoms so you would think it could be this so Worth a check.

I will kick myself if it is something like this but either way just want to get it resolved.

 

[finch wxm]

Can you check resistance between alternator body and block, I suspect the powder coat might be insulating the alternator mounts so they are not grounding to the engine block. There is no earth wire or strap between alternator and block (or batt neg) so the current return path is though the mounts.

If this is the case, I would not be surprised to find the alternator case measured at 12V relative to battery neg.

EDIT* Seeing as you have tried two alternators, and had them tested I am convinced the powder coat is your issue here, you can confirm that by connecting the alternator case to the batter negative terminal with a jump lead. But I would start by measuring resistance between alternator case and engine block.

Good call , removed alternator and brackets and the comtact faces to the block had powder coat on them ! Removed this and refitted everything. Had solid red immobiliser fault then 🙈.

Disconnected white plug of death and reconnected and all good !

Any ideas on thw white plug of death , ive cleaned up the contacts but must be wire that gets disturbed that causes it.

 

[Robbie Corbett]

White death plug might have the alternator charge wire going through it?

Otherwise, the contacts can be a right dickhead to clean up.

 

[finch wxm]

White death plug might have the alternator charge wire going through it?

Otherwise, the contacts can be a right dickhead to clean up.

Rob it does, i looked into this , i depinned it from the block. And cleaned up with contact cleaner and a file.

I think i need to put some form of water resistant to stop them corroding.

 

[Robbie Corbett]

I used silicone grease, packed both halves with it. A year later and it's still working.

 

[finch wxm]

I used silicone grease, packed both halves with it. A year later and it's still working.

Will give this ago, just seem to love the moisture

 

[Robbie Corbett]

Will give this ago, just seem to love the moisture

Good luck!

Trouble is once you abrade them a bit and remove the tin they are more prone to corrode so packing with grease is a must. Others have popped the crimped bits out of the connector housing one by one and closed them up a bit too which would have been my next move if mine didn't start behaving!

Sounds like you making progress anyway

 

[finch wxm]

Good luck!

Trouble is once you abrade them a bit and remove the tin they are more prone to corrode so packing with grease is a must. Others have popped the crimped bits out of the connector housing one by one and closed them up a bit too which would have been my next move if mine didn't start behaving!

Sounds like you making progress anyway

Yeah it was bugging me the alternator but being a renault always be something. Hopefully can just push on now as that was not giving me motivation to get it finished