# Alternator confusion.....



## 102172 (Dec 22, 2006)

Hello all.

I haven’t been active on here for a while as once more I have been off on a tour of nasty places courtesy of her Maj! And a great time I had too…….

Now I’m back and the weather is improving it is time to get the RV out a gain. However, as always I’m after your learned advice.

Just before it came off the road for winter (ie the last time I managed to use it properly before I disappeared off……) the alternator went. What a pain. I spoke to Duncan who did some digging and discovered that he would have to get one from the states at about £400 – 500 and it would take quite a long time to arrive. So I sent it off to an alternator rebuilder that I had used in the past and who always did an excellent job, to see if they could do something with it.

They could. They replaced regulator and bench tested the alternator and all seemed good. When I first fitted it all seemed good too. But after an hour or so it was clear that it was over charging….. all they way up to 19v.

So it went back and they discovered that the regulator was dead. 

Basically, the connections on the alternator are as follows:

1. A big fat high current connection that goes from a connection on the main body of the alternator to the battery.
2. On the regulator there are three connections:
a. A direct connection to the battery that the regulator uses to sense the battery voltage.
b. The link to the alternator warning light and then up to the battery.
c. A tacho link that on this vehicle is linked to the last connection on the alternator….
3. A single spade terminal on the main body of the alternator that is connected to the tacho output from the regulator – no one seems to know what this is for. But the connection is there and is good.

And the failure mode was that the voltage sensing connection (2b) was shorted to the alternator body. Hence, when ever the alternator was plugged in it was linking the battery to earth. Luckily there was some resistance in this so all it did was flatten the battery after about 24 hours.

So, after the alternator went back for a new regulator it came back and after fitting it I had the same problem. At this point I am suspecting a problem with the electrics on the vehicle. However, they were working fine before the alternator originally went. But there are only three main wires:

The main battery feed which goes to the battery – OK.
The regulator sensing wire, which goes to the battery – OK.
The alternator warning light wire – OK, in that when you put the ignition on and short the wire to earth the light comes on and when the alternator is running it goes off.
The tacho output remains connected to that other terminal on the alternator (disconnecting it makes no difference) and the alternator guys tell me it is irrelevant anyway.

The alternator will be back again with a new regulator in the next couple of days having been bench tested for an hour and proven to be fully working. I expect that the problem will still be there.

Can anyone see what I might be missing or what I am testing incorrectly? Is there a diode issue somewhere? Basically, why is the regulator being killed so quickly and not regulating, or is the fact that the battery is being over charged killing the regulator – if so what is causing the over charging/fooling of the regulator?

Arrgh! Can any one please help? This is driving me mad!

Many thanks in anticipation………

Paul

(There's a good quantity of beer in it for anyone who can help me fix this........)


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## cabby (May 14, 2005)

sorry not able to help but am bumping you up again in case there is someone who can.

cabby


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## johng1974 (Jan 17, 2007)

cant help Paul

I assume the pulley is the correct size? can't see why it wouldn't be.. if it was to small the alternator would run too fast..

Will have a think

whereabout are you out of interest?

John


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## johng1974 (Jan 17, 2007)

grabbed this

_
it may be that your ground and positive on the starter as well as on the battery are bad, bad connections cause power surges which can blow the rectifier in the alternator or other circuts.( also low battery amps)
you also may have one of your accessorys draining to much current & causing the alternator to work to hard,then eventually failing. _


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## cabby (May 14, 2005)

Just as a matter of interest have you checked the condition of the vehicle battery and the leisure batteries.they can demand a high demand if faulty. Have you tried disconnecting the leisure charge relay,so that the alternator is only charging the vehicle batt. see what the demand is just on that.this is of course after you have checked the batteries all round.Do this without the EHU connected.As a thought have you checked when on EHU what the leisure batts are reading.
Keep us updated on how you get on in case i get a brainwave.

cabby


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## 102172 (Dec 22, 2006)

Hi all,

Many thanks for the replies so far!

Perhaps I should have added the following two nuggets of info:

1. This is still the same alternator that originally went boobs up, so the pulley size is the same as it's the same pulley. I should have made that clearer.
2. This isn't the original alternator as fitted by Ford. Ford fit a standard 75A job to this engine, but HR upgrade it to a 110A job in their factory (thanks to Dunc for that info). It has had this alternator all of its life. 

From the above, I'm pretty sure that alternator should be able to handle any load applied from the vehicle. And in any case, the alternator can only supply up to the rating of the regulator, I thought? 

I will make sure I disconnect the leisure batteries before starting though (had thought of that but haven't yet tried). Both the leisure batteries and the vehicle battery are in good condition. Although I will run the generator for a few hours before start up to make sure they have a good level of charge in.

I will also check the connections on the starter and the main engine earth, although I have checked continuity and all seems good - it starts fine too.

Once again, many thanks. I'll keep you updated.

By the way I'm in Northwood, near Watford (NW London just inside the M25).

Any other advice would still be gratefully received!

Cheers.

Paul


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## cabby (May 14, 2005)

My thoughts on this to keep it basic, it will only go up to 19volts either on demand or if the regulator allows it to.
You say you have checked the earth cables for a clean and tight connection, this includes the engine to chassis straps.no other cables are getting warm or hot to the touch when vehicle is running. have you run the engine with the alternator unplugged.is it noisy at all.any sparks etc.
After all that,assuming that you have more than 1 leisure batt, isolate each one and see what the charge rate is on each whilst running.then as you re-connect check charge rate again.
it is all very long winded and time consuming but if meters don't show fault then it is all down to old fashion leg work.
am really interested now to know what the fault is and if I was still living up there would stay until sorted.

cabby


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## chrisjrv (May 7, 2007)

just a thought, are you trying to run an inverter?


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## 102172 (Dec 22, 2006)

I do sometimes, but it is turned off at the moment and has been since the troubles started.

Cheers.

Paul


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## 107088 (Sep 18, 2007)

*Nothing to do with the post but....*

I'd just like to say ( and I'm not trying to romantasise here) thanks for what you do. 
My eldest is currently serving in Afganistan and it seems few civvies pay proper respect for those who serve.

P.S. black mafia, back when we still used flintlocks.


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## NEV3 (Feb 7, 2007)

Hi Paul

I had an identical problem on my Gulfstream Sun Voyager about 5-6 years back. Also had the alternator and regulator changed (twice), to no avail. After weeks of investigation it turned out to be a BAD EARTH RETURN cable from the engine compartment (rear) to the battery compartment (forward). It didn't help that we had no circuit diagrams and the UK dealer was not helpful at all!! I don't know if they have improved on later models (I now have a 2003 Holiday Rambler, Vacationer, which on initial cursory glance looks to be improved), but at the time the wiring loom was like a bowl of spaghetti and all the wires were the same colour.,

Hope this helps you.

NEV3


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## 92046 (May 1, 2005)

*Alternator*

Hi

Bad earth, or dry battery,

You say the battery is OK, so lets go for the bad earth,

The earth terminals may be tight, but that does not mean you have a good earth, the terminal will get hot if you have a bad earth, also when the engine heater plugs are ON the voltage will go very low,

Test the strap from the engine block back to the battery first, then test the Pos + cable from the alternator to the battery,

I had trouble with the neg - cable on the engine, after cleaning it up, fitted a second earth cable from the battery to the starter bolt.

Good luck


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## 102172 (Dec 22, 2006)

Ah, thanks for that!

I have done a cursory test of the earth leads etc, but a more thorough one to follow I think! I might even put new ones everywhere, just to make sure.

Cheers.

Paul


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## pippin (Nov 15, 2007)

Come on Paul, get it sorted - 

I happen to know that he has a Masters Degree in Electrical Engineering!


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## 102172 (Dec 22, 2006)

Ok, here's the latest...... 

Firstly, anyone got a pot of sleeping tablets handy??? I have now lost the will to live..... 

Right. Got the alternator back and refitted it after checking that the new regulator wasn't down to earth as the old ones had been on removal. All seemed ok. I then ran in a new engine to chassis earth and ran one from a bolt just below the alternator directly back to the battery. I also put in a second main charge cable from the stud on the alternator directly back to the battery. I also ran in a second wire from the battery through a fuse to the sensing connection on the alternator. So I now know that the earth for the engine and alternator are definitely good and that the connection from alternator to battery is good. I also know that the sensing connection on the regulator has a good connection to the battery and is sensing the correct voltage. I also cleaned up the actual battery connection clamps. 

On starting the engine all appeared good. Regulating at spot on 14.8 volts and steady as a rock. Gradual increase in revs and still steady as a rock. Left it for a while, still 14.8 volts. Hurrah, I though.... sorted! But no! 

If I blip the throttle quickly so that the revs rise suddenly the damn thing puts out 19 volts and the warning light comes on. When I release the throttle it drops back to 14.8 volts. If I open the throttle gently and allow the engine to get to quite high revs it stays at 14.8 volts. It seems to be the speed of engine revs increase that is now the problem. Speed the engine up quickly, even a little bit, and the alternator starts producing 19 volts. Speed it up slowly, to high revs, and it stays fine at 14.8 volts. 

I've even tried another battery. No change. All of this has been done with the leisure batteries out of the vehicle and the leisure circuit isolated. 

The new regulator HASN'T blown this time and hasn't gone down to earth. 

Any thoughts? I getting desperate! Please..... 

My thoughts are as follows..... 

I think that I did have a connection problem which is why I have been blowing new regulators (thanks for the suggestions, guys!). This seems new. The guys who have been rebuilding the alternator have told me that they aren't sure why the tacho output from the regulator has a connection back onto a pin on the alternator body. Connecting and disconnecting that link makes no difference to anything, by the way. So, is it possible that this alternator has a secondary regulator system which senses revs? Could that be why there is a feed back from the regulator into the alternator from the tacho connection? Could that secondary system be what is now knackared? Can anyone think of anything else? I think I need to bite the time/cost bullet and get a new alternator in from the states. The wiring and battery are definitely good. 

It is really odd, as it seems to be regulating correctly now until I blip the throttle quickly. 

Guys I'd be really grateful for any more ideas. 

In desperation, 

Paul M-J


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