Club 80-90 Forums

Mine produces a burnt electrical smell.

What's the low down on alternators please? Get techy-speccy if you feel lke it, i'm here to learn.

Why do they burn out?
recon/ replace/ 2nd hand?
ratings and is there any benefit from getting a higher Amp rating? ie 65A/45A
What additional parts are necessary when fitting one?
Anything I need to know would be of great help.

Good to be back in blighty after a seriously long trip around France and Spain. One tank of Diesel = approx 550 miles.

Possibly the diode pack?

I had one fail and called out AA on a trip down South Coast... AA man said '... you're a lucky boy, have had a zener pack for one of these for ages, doubt if other AA vans have any'

Fitted it in 20 minutes and off we went, perfect - so there's a ruse!

Good auto-electrican would poss be cheapest fix, or refurb from GSF and then abother refurb from GSF in 2 years time if you're lucky!!

Also could ssk for a 2nd hand one one on here, and then get yours fixed by AE as a spare, always worth having a spare alt

Two in a month from GSF

shouldnt get a burning smell from the diode pack, plus your charge light would come on all the time if it went. sounds like its not worth repairing, more than likely a shot rotor or stator so i would suggest complete replacement from a decent source.

pcuk wrote:shouldnt get a burning smell from the diode pack, plus your charge light would come on all the time if it went. sounds like its not worth repairing, more than likely a shot rotor or stator so i would suggest complete replacement from a decent source.

I got a 90A job on my T25 which is brill but it do need the belt to be ggod and tight or it squeels like a stuck pig when you start up after an overnight stop! Just a point though none of them like oil in them as this contaminates the slip rings and does the electronics in.
Cheers
Ken

Can they be disassembled easily to clean innards if the diode pack seems good, charging but not very well?

yeas, normally 3 or 4 through bolts holding the lot together, remember to mark the two halfs so it goes back together with the right swing, also keep an eye out for any plastic insulators and remeber where they go. not sure if the haynes has an exploded diagram but they are very useful.

Many thanks for the replies. I have continued to use the van and the smell seems to have gone aside from a little residual stink when up close to the alternator.
I reckon you're right about recons so i'll pick up a new one and have it fitted.

Regards,

Hypnovan

Just some thoughts which might be of use. These came from an auto-electrician today while he was sorting out my charging problems. My VW is also a 1990 TD syncro and, although it now has an AAZ engine, it still runs the original JX type alternator.

First of all, with regards to fitting the 90A alternator and needing to get the belt 'really' tight. In his view, the standard v-belt cannot handle more than the standard 60-70A alternator. Even with that, you get some slippage and then wear on the alternator pulley which changes the shape of the belt faces and reduces grip further. If you want more amps, you really need to go to the flat, toothed belt drive used on modern cars. Having a really tight belt will also knock out the rear bearing of the alternator and probably the water pump as well.

The slipping belt will get very hot and burnt - maybe that is what you are smelling? I hadn't noticed any smell but I do now have a new pulley and belt fitted.

Other things he found which didn't help the charging included - burnt main terminal on the alternator and slightly resistive (rusty?) main engine earth point. These combined with a worn starter (recently changed) had lead to poor charging; low volts; high starter current (causing the burning); sulphated battery; etc, etc. What really killed things though was that the sensor terminal stud on the alternator had obviously been very tight (rusted?) and had turned slightly when the nut was removed. The problem with that is that it is soldered to the diode pack inside the alternator and, in my case there was only an intermittent contact resulting in intermittent charging.

Just replacing the battery would have lead to another damaged battery in short order. Adding a new alternator and battery would have been a major improvement but not the whole answer. Sometimes you just have to go through everything in a methodical manner and with the benefit of experience and understanding.

I hope this is useful to someone - I have been racking my brains to try to understand the erratic charging and discharging over the last couple of weeks.

Garyd

Interesting Gary...

I have beenm through much the same these last two or three weeks since coming back from long trip with a starter barely manging to whine its way to clutch engagement, a mild thump then fortunately my engine will start if it just gets turned over a couple of compressions... so kept starting.

until it wouldn't one day, even turn it over a couple of times!

Changed starter, nope, but knew original was at least not 100%, sticky solenoid clutch device etc. and suspected bad commutator too.

Anyways, thinking it could be almost any combination of the BIG 3, and having taken quite a few voltage readings, I...

1) Bought and fitted a new starter... (so have reasonable spare, my original spare)

2) Put the battery on a good charger for 24 hours, noted it said it had charged it fully, 13.6V, and was showing about 13 V after having left for 6 hours.

3) Removed alternator, disassembled and cleaned about 1/2 pound weight of Pyreneean dust/soil out of it, cleaned critical contacts within and without, esp. diode pack that has a tag/sprung contact strip, refiited and tightenmed the alt belt (yes, when batt discharged will squeal if not pretty tight)

4) Ensured all battery and earths and connections in good nick, used Holts No-Crode, checked earth resistance and battery-to-engine-and-body voltages Vs battery terminal voltages... all OK now.

Now charging at 14V measured, battery sitting at 12.8V after a night resting, starting beautifully and hope all is well in a few months, if not will have to determine Alternator Charge Current under load.

Conclusions:

2,500 mile journey with invertor/computer on a lot, alternator getting dirty and belt slipping a bit, maybe a bad contact in alt, but battery eventually got low, despite being a good 'un which came with vehicle years ago...

Always try a long slow battery charge, and see how it all sounds and how long it takes to get back to poor starting again...

NB. Batteries, starters and alternators have gone up in price a lot in last 6 months...

As you say Gary, all 3 need testing as a group!

HarryMann wrote:Interesting Gary...3) Removed alternator, disassembled and cleaned about 1/2  pound weight of Pyreneean dust/soil out of it, cleaned critical contacts within and without, esp. diode pack that has a tag/sprung contact strip, refiited and tightenmed the alt belt (yes, when batt discharged will squeal if not pretty tight)

I agree that the synchronous drive belt would be a nice option and may see if I can source the pulleys and belt if ever it gets anywhere near the top end of my priority list. I dry sumped my boats Ford Kent 1600Xflow using a 1/2" synchronous drive belt but might be inclined to use a 20mm for an alternator (simplistic calculation: 90A X 12V = 1080 = 1080/746 = about 1 1/2 HP) I took my boat to Aix again this year and found that I had to thrash the thing flat out for quite a distance before the alternator cut in. Not nice in a posh place like that says he discretely placing his baseball cap under the seat. You don't need to be at the wrong end of a 12 mile lake with a flat battery though! I guess it might be muck on the slip ring as water can find its way into the engine bay and get picked up by the flywheel etc. So thanks for prompting me on the strip down. My alternator/starter man has folded up now and I am DIY or exchange. I must be getting soft as when I started mucking with engines and stuff fifty years ago everything that went wrong would get a thorough strip down and refurbishment attempt (sometimes fatal) before going to the menders. That's how I got as clever as I think I am... CheersKen

Okay, so if I change the Alt. the best thing for me to replace it with is a new one with the same rating. For some reason I can hear other forum members saying that my engine was designed to be used with what it has so don't mess with it.
I sort of lost the thread towards the end so i'll read it all when I have figured out how to do the next bit.....an oil change. (see new posting on that if you fancy).

Thanks y'all,

Hypnovan

I've recently put a new alternator on my van...and then found that the warning light was the fault. You can have the old one if you want; although I didn't check it out I think its OK. You will need to transfer the fan and washers, key and nut from the old one but that only takes 5 mins. Do'nt have email at home so ring me on 01623 812788 if your interested.