fuses and relay positions? rad fan wiring

[Shaundon]

Hi

From what you say I assume you have the 3rd wiring diagram for the 450/500 w fan shown here with the thicker 4.0mm wire brought into play by the relay (J101)

https://club8090.co.uk/forum/download/file.php?id=1962


I have the wiring from the 2nd wiring diagram that is for a 200/300W fan - as can be seen from the diagram there are 2 - 2.5mm wires and the 2nd 2.5 wire (red) is brought into play when the 2nd or high speed switch closes and activates the relay via the 1.5mm red/blue wire. Note this 2nd wire still goes through the same fuse S1. The only difference with the wiring in my van is it goes through an 8 amp fuse in position 7 of the early fuse box instead of the 30 amp fuse shown(S1).

Sorry if my earlier description wasnt clear but I do understand how the relay works and what is going on with this wiring now ive studied it.

[CovKid]

I'd say I have the same set up as you. Without seeing further up inside your dash, its impossible to say, but mine too is fused in the fusebox. I don't have a 30 amp fuse put it that way. I still say this is likely to be caused by poor contacts though. Cleaning all connections fixed it on mine and I wasn't actually expecting, or looking for problems on the low current side of the relay. A 16amp fuse should be fine (mine is 16amp).

You have to remember that when new, an 8 amp fuse may (and I say that cautiously) have been 'just' sufficient but as the motor ages it draws more. mostly on start up. The blower motor is a prime example of that. These fuse boxes are only rated at 10amp which is why I pulled the fan circuit from the fuseboard and fitted an inline one. It fixed it anyway. I did the same with the blower fuse (I put this in the WIKI) as VW for some reason put the blower and wipers on one fuse too so if one went, they both went. Fitting a new fan would probably restore the equilibrium, something I plan to do.

Clearly there have been issues with fans, blowers and wiring as VW progressively modified the setup and even now, blown fuses are common with motors that may be around 30 years old. Windscreen wiper motors under load can also create problems in some instances and all these things result in people fitting bigger fuses and unfortunately this can lead to a fire on the odd occasion. With the tendency for moisture to work its way in via the front, the dash can be a hostile place for connections and in my case the heat build up was due to corrosion on the low current side of the fan relay.

I'm just not physically up to the job of scrabbling under the dash until later this week, plus time is an issue for me. In any event, rather than dig in too deep with diagrams, particularly if it all worked before, try cleaning contacts first and see if the problem persists.

If you have no relay (unlikely) or you're just not happy with the setup, rewire accordingly but it has to be worth cleaning everything up first, starting with the earth crowns, relay and fuse line. Then go from there.

[Shaundon]

No worries CovKid, no rush, but would be interesting to know, when your ready to have a look , if you have the thicker wire through the relay like diagram 3 or a 2.5mm wire like diagram 2. But as I say no rush as the fan has never hit high speed anyway in the 3 years ive had the van so a few more isnt gonna hurt.

Will get a wire brush and give it all a good clean up anyway..

[CovKid]

I think it'll be 2.5. The later vans used a much heavier relay for the bigger motor and cable to match.

On these 84/85 models the relay was similar to a headlamp relay (30/40 amp?) - which is enough for the job on what would have been (then) a new 200-300 watt motor. I think the 8amp fuse protects the circuit when fan is at low speed (fine) or alternatively when its simply switching the relay for high - also fine.

If the fuse was blowing even with fan at low speed, I'd suspect fan straight away but if its only causing it to blow when you switch to high speed it is almost certainly a fault in the primary side of relay and not the load induced by the fan motor at max - which takes a different route entirely.

Since the fan speeds up, the relay obviously works but the natural conclusion (and the one I drew at first until I figured out what switched what) is that its this draw from the fan motor that is blowing the fuse everytime when in fact there should be little or no load on the 8 amp fuse at all. Its just a coincidence.

That was my reasoning and how I finally nailed the cause. It was such a poor connection, it was heating up the cable and fuse. I would imagine that if the high speed fan doesn't normally come on in yours and your temperature has generally been fine, over time the unused (if not neglected) relay terminals and other spade connectors on that circuit get furred up. Once its needed, the cable and fuse get tested....

As an aside, I've removed all the power hungry stuff from the fusebox over time and it only has 8amp fuses in it now. I've bought a more modern (12-way) fusebox (below) with spade fuses to replace it entirely. I just haven't had time to complete it. All the other ancilleries added to the dash are already on a smaller and separate 8-way fusebox screwed under the dash - also blade fuses (easier to get than ceramic ones).



The problem is, once you get corrosion on all these connections, even if you clean them, it will tend to reappear months or a year or so later so new spades might be better. This is why earth crowns are such a constant annoyance. I always think they'd be better as ring connectors under nuts and washers - for longevity.

[bigherb]

Does yours have the two separate fan switches or a single three pin switch?

[Shaundon]

its all fixed - ended up wiring a new 40 amp cable back to the battery through the bulkhead and put a 30 amp fuse inline - .
All working on low and high speed and nothings getting hot - the thermo switch is the single 3 pin variety.

Cleaned up the earth crowns too but would like to get new ones if possible - can you buy them anywhere??.

S.

[CovKid]

Jeesh, thats heavyweight. You got a rolls royce engine for a fan?

[Shaundon]

yeah - best safe than sorry i thought in the end

- gonna add a newer more modern fuse box like you've done eventually and move some stuff off the old one , thought an extra cable back to the battery would add more current carrying capacity for future expansion...

cheers for the idea

would like to replace those earth crowns too but not having much luck finding anything suitable...

[bigherb]

Cleaned up the earth crowns too but would like to get new ones if possible - can you buy them anywhere??.

S.

Not from VW any more. The part number is 191 971 519 ground connector, if you can find them anywhere.
Or if you have a Case/Steyr tractor dealers near, they use them as well. Part number 1-40-277-013

[CovKid]

I'm inclined to fit an earth bus bar as it may be less prone to corrosion than those earth crowns. There are several types on the flea.

Will start work on fusebox over the next two weeks. Not sure which type I'll fit (bought another sort today) but be glad to see the back of that blasted ceramic fuse holder. They were OK on a bug but a bit lame in a T25 what with all the gadgets you end up fitting. Purists may choke at the idea but I struggle to bend my head under there now, plus I have to wear thick reading glasses just to see if a fuse has gone. Best bet might be to site new box, run a chunkier cable from the battery then move everything over bit by bit and as near to the original fuse order as possible. Spade connectors to original fusebox may go too - decided I'll solder on decent ring connectors if I use this other fusebox.

Once thats all done I can rewire the headlights which have always given me grief and fit proper relays for them.

I'm getting there - starter and alternator are all completely rewired now. Check it out if youi've not seen it Shaundon. https://club8090.co.uk/wiki/VW ... ain_cables" onclick="window.open(this.href);return false;

[Oldiebut goodie]

I've got them bliddy fuses in my Merc also, checked my lights before the MoT - all OK, failed MoT due to light not working. All it was was the bumping on the road had moved the fuse so that the contact was on and off. I could do with replacing that lot also, luckily there are no relays on the board to contend with though.

[Shaundon]

good write up CovKid, think I'll check those cables on my van, love the home made copper lugs.

This fuse box looks interesting as has built in earth bar...
http://www.autoelectricsupplies.co.uk/p ... ategory/63

This is the nearest i can find to the earth crowns

http://www.thetoolboxshop.com/0-005-35- ... -8406.html

LED blade fuses are good if you wanna spot when they go easily.
http://www.autoelectricsupplies.co.uk/p ... tegory/157

[CovKid]

Yep, first link you gave to fusebox was the one I bought recently. The problem with existing T25 ceramic fusebox (apart from its limitations in terms of amps) is because it uses spade connectors and VW crammed sometimes two items per fuse, it all takes up so much room at the back. The issue isn't quite so bad with ring connectors as you can at least stack them although I'd rather everything had its own fuse anyway as far as possible.

In an ideal world fuses would be easily accessible up top somewhow, much like trucks, but with existing wire lengths etc, that may prove incredibly difficult - plus where? I'm not precious about the dash and don't mind say cutting the ashtray (now unused) back into the perforated speaker mount behind it, and fitting a snug lid for the new hole, but its not a job I'd rush at without thought - a rewire nightmare too. Probably easier to just make a drop-down hinged mounting close to or in original fusebox area so you can swing the box up without having to get on your knees. It does annoys me the way the glovebox was cut away to accommodate the stock fusebox - looks untidy if not heath-robinson. I'm damned sure VW do better fuseboxes than that now. They must have put the trainee lad on that job