low volts

[irish.david]

The problem with adjustable regulators is that they're not a solution to the real problem and all they do is mask the symptoms. They could also potentially cause problems with damaging your engine electrics due to overvoltage.

Your current regulator will regulate the voltage at around 14.4V at the output of the alternator. This is then connected to the junction box that supplies the engine electrics, goes back onto the main starter motor terminal before going down your main starter motor cable and onto the battery. If the cable and all the connections are all shiney and new, the resistance will be very low and almost all the energy produced by the alternator will end up in the battery. After years of use, the cables and connections aren't so good anymore and they develop a small resistance and this limits the amount of energy that can flow to the battery and this can be observed as an increased voltage drop.

Due to the the way electrical systems work and batteries charge, a small resistance increase that causes a small voltage drop can have a disproportionate effect on the amount of energy that reaches your battery from the alternator. This is made worse by the fact that the amount of voltage drop between the alternator and battery increases with the amount of current that flows through the wires, so a flat battery that pulls more current will produce a bigger voltage drop.

If you use a variable regulator that maintains a steady 14.5V at the battery, your battery will always charge at it's maximum capacity but if you haven't renewed your cables then you have to consider how it's going to achieve this. You mentioned earlier that you get 12.5V at the battery at the moment so that means that when you measured it and assuming your alternator was outputting 14.4v, you had a voltage drop of about 2v from your alternator to your battery. If you use a variable regulator then your alternator would have to output 16.5v to produce 14.5v at the battery and that's where the problems start. The first thing the alternator is connected to are the engine electrics which will have a maximum voltage rating and if the output of the alternator exceeds that, then you'll burn them out.

The problem is made worse by the fact that as the battery is now charging at 14.5v it'll draw more current than it is now, which will make the voltage drop worse so the alternator would have to output a higher voltage to maintain the 14.5v at the battery. And the problem will get worse over time so even if your engine electrics don't burn out straight away, as your cables and connections get worse you'll get to a point where the alternator output gets high enough to cause a problem.

You could use an voltage regulator for your engine electrics or other roundabout ways of masking the problem, but the only problem solution to the problem of voltage drop in vans of this age is replacing the cables in the charging circuit.

Dave

[ghost123uk]

Good post Dave

[California Dreamin]

Good post Dave

If it was accurate......are we saying all the rear engine electrics take their feed directly from the alternator, that these electrics don't go all the way back to the fuse box at the front?. And what are these engine electrics that will burn out?

The logic is sound and of course, using a sticking plaster to mask the illness is not the way, however, it is accepted that the 'petrol engined' T25's are unique in having the starter battery and main wiring feeds (fuse box) well up front and the alternator/starter circuits, 5 metres away at the rear.....there will always be a voltage drop in these circumstances especially under load.
I would suggest that it is the degree of voltage drop that determines whether this (an adjustable voltage regulator) is appropriate.

Lets not forget that Smosh measured 13.5 volts directly at the alternators output and not 14.4 volts as suggested was a good figure by Irish.david. It is clear that there is a basic charge issue which needs fixing first and if there is a 2 volt drop between the alternator and starter battery then the condition of the wiring may indeed need looking at. However, we need to eliminate the possibility of other circuits (namely the second auxiliary battery if it has one) that might be pulling down this reading due to a battery fault/short etc.

Martin

[Timwhy]

This was from the Aircooled site that I posted, explaining the regulator.



All of these symptoms can be fixed for good by adjusting the charging voltage at your battery to 14.5V, by installing this regulator, it takes 10 minutes to do! Many customers have reported their "charging voltage" in the mid 13 range, which is pitiful! Our personal Vanagon charged at 13.7V, which meant the battery was never fully charged, and headlights were not full brightness! Adjustment is done with a small screwdriver in the hole you see in the back of the regulator; simply rotate the screw clockwise to increase voltage, or counter-clockwise to decrease voltage, you want to shoot for 14.5V AT THE BATTERY.

The regulator is quite sensitive, small adjustments make rapid changes, so go slowly! These regulators are factory preset to 14.5V, which is a great voltage to start with. We do not recommend higher than 14.5V, even though the regulator will adjust up to 15V. You do need a volt meter MEASURING THE BATTERY to properly set the regulator. We strongly discourage using dash gauges for this purpose, since there are too many things that can cause inaccurate readings!

It states that they come preset at 14.5 volts and the regulator can only go as high as 15 volts. I would suspect that there were an issue at the alternator, maybe the installed regulator the OP has is faulty or the alternator itself?

[CovKid]

Again, the above would be true if wiring has been renewed or is in exceptionally good condition before you fit one. All the campers I've seen fail that miserably (at least in the UK where rain and salt plays havoc).

I'd be quite happy to try an adjustable regulator now my main cables have been replaced and properly terminated as they are now as good as they can be given the distance they run. I do think its important to start there as the need for a bigger or adjustable regulator may become less of an issue once the basics are done. Then its a bonus.

Otherwise its almost the same as saying "fitting brighter bulbs will cure your dim ones". Its only half the answer.

Pretty much what Dave said in fact.

[irish.david]

@California Dreamin

For petrol engines with unmodified wiring the feed from the alternator goes to the junction box on the left hand side of the forward end of the engine compartment. Anything that comes off the the metal post in that junction box is fed straight from the alternator and on my van that was all the engine electrics. The wiring then goes to the starter motor and on to the battery. To be honest, a good way to instantly improve the charging situation on your van is to run a decent bit of cable directly from the alternator output to the main terminal on the starter motor.

It's true that they'll always be a voltage drop across any cable, but this is directly proportional to the resistance of the cable, so by minimising the resistance you minimise the voltage drop. When VW designed the electrics they used the smallest cables they could get away with to save money and 30 years later the same cables have degraded along with the connections and terminations and this increased resistance is causing real problems.

I was just using the numbers from Smooshs case as an example of why simply increasing the voltage from the alternator wasn't a real solution to the problem. I agree that if his alternator is producing 13.5 volts then there's more going on there than old wiring.

@Timwhy

The numbers i was using were just used as an example of why increasing the voltage at the alternator isn't the correct way to solve the problem of voltage drop and i disagreed with the post on Aircooled that suggested this. If you have a properly working alternator then increasing the output voltage isn't the right way to fix voltage drop at the battery.

An analogy would be fixing partially blocked pipes by simply increasing the pressure at the supply.



The worst offenders in the charging system is the cable run from the alternator to the starter motor terminal (via the engine junction box) and the engine earth strap. If you run a length of cable (16-25mm2) from the alternator output to the main starter motor terminals (giving both a clean) and the same cable size from the alternator body to a good chassis earth you should see a much smaller voltage drop.

Dave

PS: I should have added that the connection from the alternator body to the chassis earth is purely for testing to see if the engine earth is contributing to the overall voltage drop. It would be unsafe to leave this wire connected when the vehicle is in use in case there was a problem with the gearbox or engine earthing strap which would mean all the current used for starting the engine would end up travelling down this wire which it's not rated to handle. If you find that wire from the alternator body to the chassis ground reduces the voltage drop then you should clean or renew the existing earth straps and consider adding an extra earth strap on the engine close to the alternator body.

[Oldiebut goodie]

To emphasize the voltage drop due to old cable and terminals, I checked the voltage drop between the alternator and battery on mine some time ago - it was 1/2 a volt which was ridiculous for a cable less than a foot long! Cable and terminals replaced (soldered not crimped) and there was zero drop. I hate to think what the voltage drop is on the petrol models if I had that on a diesel setup.

[Timwhy]

The worst offenders in the charging system is the cable run from the alternator to the starter motor terminal (via the engine junction box) and the engine earth strap. If you run a length of cable (16-25mm2) from the alternator output to the main starter motor terminals (giving both a clean) and the same cable size from the alternator body to a good chassis earth you should see a much smaller voltage drop.

Dave

With my current setup, new alternator harness, ground cable from alternator to engine/transaxle and a hard start relay to starter. I am not looking to over compensate for old wires, just trying to offer suggestions to the OP. Changing the long wire to the battery would be ideal and making sure your alternator/regulator is in fact working correctly.

[CovKid]

Would echo all of that. Even in my WIKI piece on this, the first thing I did was fit a whopping fat cable from alternator to starter and the same from starter to battery. Its meatier even that the harness used by Tim although I took the view that going big removed any doubt. I really detest starting/charging issues so just went extra heavy-duty.

The troubling bits (or at least very time consuming) was making up the cable ends. It takes a certain amount of practice to guage just how much the outer sheath will shrink back when you apply solder, as well as just how much to apply - and at what angle. Then I fitted shrink tubing to seal it properly.

What tends to happen over the years is strands break away and acid corrosion makes it almost impossible to work with the existing cable. It didn't matter how far back I cut the starter to battery cable, it was just past its best. You can't solder stuff like that. The alternator cable/s fared no better.

I'm fairly sure the reason VW took the alternator output to that post on the left was wholly down to the way the vehicles went through the assembly line. Admittedly they double up the cable but I agree, straight to starter motor is best and thats exactly what I did.

I think we're all in agreement that just 'upping' the voltage from the alternator definately won't fix the problem, but in conjunction with a complete overhaul, it will certainly help.

Incidentally, I also upgraded the cable from battery to fusebox where it now terminates in an insulated buzzbar. Not the easiest job to do, but at least you're maximising what you can get from your system and tapping into that using headlight relays is ideal. The existing supply line is a bit feeble when you consider the multitude od add-ons and upgrades everyone seems to fit now. In the 80s you were lucky if you had a 10 watt cassette radio and most bulbs were tungsten.

By far, replacing the main cables and moving to an electric fuel pump completely transformed the reliability of mine. Excellent upgrades.

[California Dreamin]

Pretty red wire.....but what additional benefit do you think it delivers, your alternator is more than adequately earthed 'connected' to the engine by the solid cast pivot and adjusting bracket....if you want to make a difference then earth from engine to chassis (bell housing to bare chassis then paint) using a nice heavy braided earth cable.
I seem to remember seeing a small braided earth strap on some of these alternators although I don't think I have one on mine.

Martin

[Timwhy]

Pretty red wire.....but why? your alternator is more than adequately earthed 'connected' to the engine....if you want to make a difference then earth from engine to chassis (bell housing to bare chassis then paint) using a nice heavy braided earth cable.

Martin

Is it?

There's a nice braided cable at the front of the transaxle to chassis and besides it can't hurt.

And Martin don't you like pretty things?

[Smosh]

I am (slowly) taking this all in, thanks for the information.

Renewing and increasing cable is going to be a must. I would also be getting a brush kit for the Alternator.

Would an adjustable regulator not have an upper limit to prevent burn out (i understand this would be low in worn cables).

I would also consider a solar and hookup charging kit. I also now know I need to charge my battery more often!

[California Dreamin]

No it certainly can't hurt....just that a braided strap close to the starter and to chassis would have made more sense and perhaps a small braided cable from the alternator body and engine (similar short braided cables are used by Volkswagen on alternators on other models) In my opinion, there is no real need for a metre long 150 amp wire back to the bell housing, although this won't hurt either.

Martin

[irish.david]

@Timwhy

I’m afraid that i agree with Martin that the red wire in the pictures isn’t really doing anything. All you’re doing is basically linking the engine earth and the gearbox earth which should be more than sufficiently earthed through contact without the need for an extra wire. Even with the wire you’ve added you’re still at the mercy of both the existing old engine and gearbox earth strap for the connection to the chassis earth. The battery is earthed directly to the chassis so you’d be better off connecting the alternator body to a good chassis earth with an earth strap if you wanted to maximise the alternator output.

Also, coming back to an earlier post where you said that the alternator output can only be increased to a maximum of 15v, this would also potentially have the effect of putting a voltage close to 15v across the battery when it was nearly full and there was a low electrical load on system (eg. no heater blower, no stereo, etc). The voltage drop on an electrical network is due to the electrical resistance and the amount of current flowing. This means that as the amount of current flowing reduces to close to zero, the voltage drop also gets close to zero. In this situation if you're driving along with a fully charged battery and very little load on the system the voltage across the battery terminals would be close to the alternator output of 15v and could damage the battery.

@Smosh

If you’re getting 13.5v directly at the output of the alternator then either there’s a massive electrical load somewhere on your system or there’s a problem with the regulator. The fact that you’re getting 0v on one of the alternator outputs also makes me suspicious. Is there any way you could post a pic showing of your alternator outputs and where you measured these voltages?

Dave

[Smosh]

Dave, I will get some pics at the weekend. Prob wont get to the van before then!