Club 80-90 Forums

I think my alternator is on the way out, I'm getting 13.5v at the battery but no increase when I rev the engine. Can anyone tell me what the output should be? I've got an early 1.9 dg.

13.8-14.5v

Check the output at the alternator, could just be poor earth / +ve cabling

Thanks, it's a 45amp model btw

The regulator inside the alternator presets the charging voltage. It may well have given up the ghost resulting in no output. Your best bet is to order a new regulator and swap yours out. The regulator generally fails way before the alternator does.

Its held on the back of the alternator with two screws. Disconnect the battery first, and you may find you need to slacken belt, remove belt, and pivot alternator if needed, to gain access to the screws.

The other possibility is that the blue trigger wire on the back of the alternator has come off, but that will usually cause ignition light to stay on.

Up to you where you buy one but GSF stock them and theres up to 57% off if you use code WKD57 https://www.gsfcarparts.com/catalogsear ... =910VG0070" onclick="window.open(this.href);return false; - will come to £10.61 at mo. Worth a try - a lot cheaper than a new alternator

CovKid wrote:The regulator inside the alternator presets the charging voltage. It may well have given up the ghost resulting in no output. Your best bet is to order a new regulator and swap yours out. The regulator generally fails way before the alternator does.

Its held on the back of the alternator with two screws. Disconnect the battery first, and you may find you need to slacken belt, remove belt, and pivot alternator if needed, to gain access to the screws.

The other possibility is that the blue trigger wire on the back of the alternator has come off, but that will usually cause ignition light to stay on.

Up to you where you buy one but GSF stock them and theres up to 57% off if you use code WKD57 https://www.gsfcarparts.com/catalogsear ... =910VG0070" onclick="window.open(this.href);return false; - will come to £10.61 at mo

Cheap fix, but better to establish if the issue is the regulator or the cabling before laying out any dosh, IMHO

Thanks for the info, will be checking this out today

I checked the wiring earlier and all seems fine, the voltage at the alternator is 14.87 but doesn't increase with revs.

I removed my regulator and it looks pretty worn and sooty so I think I'll replace that anyway, I'm slightly confused with getting the correct part though. The original part has the number 1 197 311 005 stamped on it.

Heritage are close to me but they offer 2 for the t25 bosch alternator:
https://www.vwheritage.com/068903803ab- ... r-vw-spare

And this one with "without resistance":
https://www.vwheritage.com/068903803dx- ... e-vw-spare

Advice welcome.

I would say the regulator is fine, no harm in replacing it if you want a spare, but you should be looking at the cabling from the alternator to the battery and earths to eliminate the voltage drop.

There's advice in the wiki, much of it from Covkid

Ok, I'll double check the cabling, I've seen Covkid's post on upgrading the alternator to battery post, will have another read.

Yep, voltage drop due to high resistance. Its quite possible that a connection that visually looks ok is so corroded (when you take it off) that its no longer passing sufficient current. A tell-tale sign would be heat at one point, so you could try running it for a while, switch off and follow the alternator output cable, feeling as you go for warmth. Starter motor terminal would be favourite in this instance. A good clean up may solve it.

Beyond that, my main cable upgrade has two benefits - better starting and better lights but I suspect you have a bad connection at either starter or from rear of alternator and you'll probably find it quite quickly now you know what you're looking for.

If cables are badly frayed and green, swap them out.

Wise to keep a spare regulator onboard anyway.