Need more Volts at the front of your bus?

[irishkeet]

Irishkeet just did his. I think he can see a rabbit two miles away now

hello CovKid not had a chance to do it yet but all the goodies arrived yesterday, but of rot to sort first before I upgrade

[Smiffo]

Irishkeet just did his. I think he can see a rabbit two miles away now

hello CovKid not had a chance to do it yet but all the goodies arrived yesterday, but of rot to sort first before I upgrade

Hi Irish.

Did you order the cables cut to length etc?
You can guess my next question if you did

[davegsm82]

Been driving out today in the bus, noted a marked difference in the speed of wipers and electric windows. Lights were also WAY brighter but I have recently upgraded from Tungsten to Halogen and not driven it in the dark since.

Starting to think perhaps the voltage increase by this mod might be better than I originally measured. I should probably measure it properly instead of just poking the meter at one of the fuses.

Dave.

[CovKid]

Before I upgraded mine, I rarely saw more than 11-11.5 volts at dash, and headlights got around 10.5v volts. Now I get around 13 volts and less overheating at main cable terminal. VW only fitted what would 'just do' which is fine if you use a 5 watt tape player and tungsten bulbs.

[davegsm82]

Before I upgraded mine, I rarely saw more than 11-11.5 volts at dash

What engine are you running? I could understand that kind of volt-loss with a diesel but if petrol with front mounted batteries then I'd be shocked.

[windy]

Thanks for the heads up on this nice & easy mod Dave.

I added the wiring link yesterday, so all thats left to do is plug in the relay when it arrives sometime this week.

Fitted Osram nightbreakers last week, as I'm doing a fair bit of night driving lately & they improved the light output a fair bit, but I can see them dim when the demister fan is on full tilt.

Will let you know the results

[Smosh]

Before I upgraded mine, I rarely saw more than 11-11.5 volts at dash

What engine are you running? I could understand that kind of volt-loss with a diesel but if petrol with front mounted batteries then I'd be shocked.

Is a very small cable supplying power to the front. I've done the same mod with great results.

[CovKid]

Correct. The voltage drop on cables that were barely adequate when new and even worse after 30 years, can be substantial. I don't like the analogy to water pipes but in this instance it seems relevant. Bigger pipes pass more water. Its in the WIKI but consider:


Propex 2 Amps
Engine 8 Amps
Lights (x2) 10 Amps
Heater blower on full 8 Amps (???)
Rad fan on full 12 Amps (???)
Radio (playing reggae !) 5 Amps
Tail lights/ instruments etc ~5 Amps
Fridge 8 Amps
Trickle charge both batteries 4 Amps

Rare all would be on at once but if they were thats 62 amps - quite taxing on the factory harness.

Heres my camper with upgraded main cables and headlight relays but using stock (cheap) halogen bulbs set in modern reflectors:
https://www.youtube.com/watch?v=cEIkGpC72GY" onclick="window.open(this.href);return false;

No more yellow light.

[irishkeet]

Irishkeet just did his. I think he can see a rabbit two miles away now

hello CovKid not had a chance to do it yet but all the goodies arrived yesterday, but of rot to sort first before I upgrade

Hi Irish.

Did you order the cables cut to length etc?
You can guess my next question if you did

hi

no I bought a 10m reel of the 16mm and a load of other bits, used toolstation for the terminals as CovKid says they are the best value

used AES for the rest as thay had the same terminal boxes as CovKid used
https://www.autoelectricsupplies.co.uk/

[bigbadbob76]

Looking at the petrol DG wiring diagrams-
Taking the feed from the rad fan high speed relay supply (fuse s1) to terminal N seems dodgy to me.
At full speed the rad fan takes 300W, that's 20-25A depending on battery volts.
Assuming (never good to assume but hey ho) that the current is split equally between low speed and high speed cables that's 12A ish as CovKid says.
A thick wire was put in there for a reason, vw didn't waste money on thick wires for no reason, and unless you never go anywhere remotely hot and your rad fan never comes on, your wiring might well get a tad warm if you start pulling headlight current from it.

Then... adding a relay in position 2 switches in the new feed to presumably (there I go again) track 30 when activated by switched supply on track 15.

Seems like a convoluted route.

I'd run one or more wires from the battery to one or more of the terminal P's on the back of the fuse box, or go the whole hog and do the full CovKid upgrades.

You could then use relay 2 and terminal N as an output to power your headlights, and/or terminal E14 via spare fuse S5, to power something else.

Fitting a big ass master fuse (100A) near the battery would be no bad thing either, as insulation ages and goes brittle it can lead to shorts to chassis and small welding fires under your ass or dash.

[davegsm82]

Looking at the petrol DG wiring diagrams-
Taking the feed from the rad fan high speed relay supply (fuse s1) to terminal N seems dodgy to me.
At full speed the rad fan takes 300W, that's 20-25A depending on battery volts.
Assuming (never good to assume but hey ho) that the current is split equally between low speed and high speed cables that's 12A ish as CovKid says.
A thick wire was put in there for a reason, vw didn't waste money on thick wires for no reason, and unless you never go anywhere remotely hot and your rad fan never comes on, your wiring might well get a tad warm if you start pulling headlight current from it.

Then... adding a relay in position 2 switches in the new feed to presumably (there I go again) track 30 when activated by switched supply on track 15.

Seems like a convoluted route.

I'd run one or more wires from the battery to one or more of the terminal P's on the back of the fuse box, or go the whole hog and do the full CovKid upgrades.

You could then use relay 2 and terminal N as an output to power your headlights, and/or terminal E14 via spare fuse S5, to power something else.

Fitting a big ass master fuse (100A) near the battery would be no bad thing either, as insulation ages and goes brittle it can lead to shorts to chassis and small welding fires under your ass or dash.

Fair comment, I've never had my radiator fan come on even in the summer stuck in traffic, which led me to test it to make sure it actually worked!

In practice you're not drawing huge amounts of current via the Fan cable, just enough to shore up the main terminal supply. The main cable (on the diesels at least) is thicker so is already the path of least resistance, if something horrible were to happen then this would be the one doing all the damage anyway.

If you really wanted to dig into it, which kind of defeats the point, then you could fit a changeover relay to the fan high-speed relay, and run the N terminal to the normally closed position, such that if the fan came on then you lose your extra feed but aren't drawing extra amps down that cable.

I'm happy with the spec of the fan cable and more than confident about it's current carrying ability so I'm going to leave this mod in place. you have to remember that if you had, say, a volt dropped across that cable because you were drawing 12A (as an example) then this is only 12W. 12W distributed over what is probably 4 or more meters of cable is not a lot of heat. If the fan does kick in then it won't be for long periods of time either.

I second your idea about an engine bay fuse, with the caveat that I would want quite a lot of overhead, 100A isn't a lot, headlights, fans, wipers, Entertainment system, leccy windows etc (if I hit both switches to the window motors stall then that's 24A instantly). Could exceed 100A easily imagine. in a serious fault condition you'd probably see a good 200A without too much trouble.

Dave.

[California Dreamin]

I have read this with interest: the one thing that occurs to me is there is little difference between battery location when it comes to lighting. Its the alternator that is producing the current, not the battery, the battery is merely storing what is produced. The current in either case (petrol or diesel) is having to come from the engine bay at the back to the fuse box at the front. The regulator also plays a significant role holding the output voltage steady. If you are unfortunate enough to have a regulator outputting only 13.5 volts at the B+ post (rear of the alternator) you are already fighting a loosing battle. My advice would be to swap out any regulator outputting below 13.9 volts for one set to 14.5 volts. I know this won't cure voltage drop in old tarnished wiring but it will definitely help and in the process better suit the newer materials found in modern batteries that require a slightly higher charge voltage to successfully achieve 100% charge.
Relaying to the headlamps and using the old wiring merely to switch the relays..is the way to go if you really want massive improvements in actual voltage reaching the bulbs (obviously good voltage needs to be getting to the front as a pre-requisite)


Martin

[ZsZ]

Interesting stuff here. Last year I soldered all the crimped connectors on my factory alternator to fuse box wiring when I had alternator problems. That also helped to raise the voltage at the front.

[Mocki]

i moved my battery from under the seat to the engine bay , it made no difference what so ever to the voltage at the fusebox, none at all.... not even when the engine wasnt running
what it did do was give me more storage inside the van, and improve the voltage at the starter motor when cranking .

[bigbadbob76]

I second your idea about an engine bay fuse, with the caveat that I would want quite a lot of overhead, 100A isn't a lot, headlights, fans, wipers, Entertainment system, leccy windows etc (if I hit both switches to the window motors stall then that's 24A instantly). Could exceed 100A easily imagine. in a serious fault condition you'd probably see a good 200A without too much trouble.

Dave.

Good point on the overhead, you'd want to balance it between not blowing if you stall the windows while running fans etc but still protect against serious faults. bearing in mind that a 100A fuse won't blow as soon as you hit 100A, there's plenty margin built in.

Its the alternator that is producing the current, not the battery, the battery is merely storing what is produced. The current in either case (petrol or diesel) is having to come from the engine bay at the back to the fuse box at the front. The regulator also plays a significant role holding the output voltage steady. If you are unfortunate enough to have a regulator outputting only 13.5 volts at the B+ post (rear of the alternator) you are already fighting a loosing battle. My advice would be to swap out any regulator outputting below 13.9 volts for one set to 14.5 volts.

Well said Martin, the battery won't miraculously produce any more voltage than the alternator charges it to.
My (petrol) battery never shows over 13.9v, I must check it at the alternator and act accordingly.
beefing up the regulator and the alternator wiring will help a lot and beefing up the battery to dash wiring will help a diesel, either way, it's the long wires that drop the most volts.
In a petrol, this is the starter wire so is already beefy.