Alternator / regulator questions

Gritty

Member
Hi folks

I have a red battery light on my dash so checked the battery and alternator last night battery is new and is not receiving a charge but alternator is working ok so been advised be my neighbour Biggdog it may be the regulator.

Checked battery terminals just in case, all good.

Battery was 11.65
Alternator 11.65 cold
Alternator 14.4 after cranking
Battery still 11.65

My car is 75 tdi AMF 2002, with lots of electrical dependant extras so its the 120a I think.

My question is has anyone replaced their regulator with the alternator in situ ? Or does the alternator have to come off for the reg to be fitted? is this an easy hard job to complete ?
 

BiggDogg

A2OC Donor
Andy,
Chiming in on this if that’s ok:

Last night the battery was at 11.65V measured at the B+ alternator terminal with ignition off, which is low but it started the engine ok.
With engine running, 14.3V at alternator B+ terminal and 14.0V at battery terminals, showing a 0.3V drop on the cables therefore charging the battery nicely, but the alternator warning lamp is lit the whole time the engine is running, and doesn’t go out or go dimmer when revving up.

Andy, I think you took it for a run to charge up the battery after, then tested the battery voltage this morning and was again 11.65V?

Did you say the lamp was flickering for a while after driving in heavy rain before coming on constantly?

The belt isn’t slipping and the tensioner looked good when we looked at it last night.

Anyone think it isn’t the regulator? - I don’t want to give Andy bad advice here. The price of new regulators that look like they’d fit on eBay seems to be from £12.50 up to £55(!) but I’m not certain of the right one without knowing Andy’s alternator p/n. Could be a used or recon alternator would be a better bet, though I have in the past successfully replaced alternator bearings and regulators at a lower cost.

Matt



Sent from my iPhone using Tapatalk
 

PaulA2

Well-Known Member
Watching this with interest as having similar issues myself. Got a very cheap tester from Halfords which suggests battery is good and alternator is ok at Idle speeds (just) however when revved or car has heavy battery pod it struggles and seems to worsen when engine speed is higher. As a punt I plan to swap pulley on the alternator first but failing that will do regulator.

battery is also newish with last 12 months and charges well with a mains charger.
 

Gritty

Member
Andy,
Chiming in on this if that’s ok:

Last night the battery was at 11.65V measured at the B+ alternator terminal with ignition off, which is low but it started the engine ok.
With engine running, 14.3V at alternator B+ terminal and 14.0V at battery terminals, showing a 0.3V drop on the cables therefore charging the battery nicely, but the alternator warning lamp is lit the whole time the engine is running, and doesn’t go out or go dimmer when revving up.

Andy, I think you took it for a run to charge up the battery after, then tested the battery voltage this morning and was again 11.65V?

Did you say the lamp was flickering for a while after driving in heavy rain before coming on constantly?

The belt isn’t slipping and the tensioner looked good when we looked at it last night.

Anyone think it isn’t the regulator? - I don’t want to give Andy bad advice here. The price of new regulators that look like they’d fit on eBay seems to be from £12.50 up to £55(!) but I’m not certain of the right one without knowing Andy’s alternator p/n. Could be a used or recon alternator would be a better bet, though I have in the past successfully replaced alternator bearings and regulators at a lower cost.

Matt



Sent from my iPhone using Tapatalk
Hi Matt yes battery still 11.65 after run and yes battery light initially flickered on/ off duiring heavy rain fall and later stayed on and is still on when ignition on.

I found a general VAG you tube vid for taking the reg off without taking the alternator off so gona investigate that on Sunday hopefully.

youtube.com/watch?v=QtyP7AyZxwg

Just thought Id ask the question here before hand.

andy
 

Robin_Cox

Member
On an AMF with 120A alternator the part number appears to be 070803903E, which corresponds to a Bosch F00MA45303. Picked one up having had the battery light come on last week (although in my case it turned out to be a missing alternator belt!) - cost around 25 quid. Says it is compatible with both the 120A AMF alternator and the 140A one on my BHC so worthwhile in the parts collection.
 

BiggDogg

A2OC Donor
Andy,
I watched that video. I imagine while its possible to fit a new regulator with the alternator in place, actually it will be quicker / less risky to take it out first and do the alternator swap with everything in good view and easy access. The extra work to remove the alternator is only 2 or 3 big long bolts after taking the multi-v belt off which is easy with mole grips on the tensioner. You have to disconnect the cables anyhow.
If you've got a spare regulator and want a hand then I'm around tomorrow (Sunday).

Matt
 

Gritty

Member
Andy,
I watched that video. I imagine while its possible to fit a new regulator with the alternator in place, actually it will be quicker / less risky to take it out first and do the alternator swap with everything in good view and easy access. The extra work to remove the alternator is only 2 or 3 big long bolts after taking the multi-v belt off which is easy with mole grips on the tensioner. You have to disconnect the cables anyhow.
If you've got a spare regulator and want a hand then I'm around tomorrow (Sunday).

Matt
Hi Matt
Just seen this message I had a go this morning but one of the alternator housing bolts/nuts is right behind the thermostat housing and I just cant get to it.
Sods law i took that off the week before to do the thermostat. gurrrr.

I ve not bought a regulator as I wanted to get the right one so thought id check out the Alternator first.

Will order one then you can show me how to get the alternator off.

Speak soon enjoy the sunshine.
 

PaulA2

Well-Known Member
Finally got my alternator up and running and getting a strong voltage registering at the battery too.

I have swapped these items in the following order:

1. The pulley (although this initially did not make a huge difference)
2. The regulator (again did not seem to make a huge change at the battery). I then checked the voltage at the alternator and used the engine to take the earth and it was showing a very strong voltage.
3. After the above steps I then removed and cleaned the earth strap behind the headlight and this then cleared all problems.

Should have checked the earth strap first as suspect this was the biggest problem.
 

Gritty

Member
Finally got my alternator up and running and getting a strong voltage registering at the battery too.

I have swapped these items in the following order:

1. The pulley (although this initially did not make a huge difference)
2. The regulator (again did not seem to make a huge change at the battery). I then checked the voltage at the alternator and used the engine to take the earth and it was showing a very strong voltage.
3. After the above steps I then removed and cleaned the earth strap behind the headlight and this then cleared all problems.

Should have checked the earth strap first as suspect this was the biggest problem.
Interesting
Im gona try fit a new regulator to my existing alternator this week if it stops raining.
Re the earth strap behind the right head lamp dosnt that go to the starter motor?
 

PaulA2

Well-Known Member
Yes I believe so but in theory it is what connects the Negative of the circuit or the alternator to the battery which is what appears to be causing my issue. Definitely something to try as well as the other elements. What is worth trying too is seeing what voltage you get when measuring direct off the alternator terminal and the engine to see how your alternator is performing.
 

Gritty

Member
Just to update
Got the alternator off on Sunday and the regulator was very worn as were the slip rngs on the alternator, however cleaned up the slip rings and applied the new regulator and put it all back together. Car now running fine with no red battery warning light, so good result

Thanks to Biggdogg for his advice and to every one above for their input.
 
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