How To Check & Replace The Charging System On A VW Beetle
Mark shows us how you check the charging system on your classic VW Beetle.
(00:00) Today I'm going to be taking a look at a 1970 Beetle that's got charging issues, the battery's been going flat over the last few weeks, so we're going to run through the charging system and see what we can find so let's check it out so the first thing I noticed is when I started the engine the generator light on the dashboard didn't extinguish it stayed on and even when I revved it it still stayed on this car should have had a dynamo from factory but has has been upgraded to an alternator so the first thing I'm going to do is check our
(00:39) charge light wire from the alternator back to the dashboard, make sure that it works correctly. So, I'm going to disconnect our charge light wire, which is this one here, put our ignition on and then put it to earth onto the alternator body and make sure the light switches on and off at the dashboard end with the ignition switched on. I can now test our generator wire, so if I put this to Earth or the body of the alternator, it should switch the light on on the dashboard and off when I remove it, and on again, so this tells me that our line
(01:09) is good from here all the way up to the dashboard to the bulb and that's sort of it's working correctly with my voltmeter and the engine running I can now test the output of our alternator foreign from the alternator initially looked quite good as soon as I loaded the circuit up by putting the headlights on you can see that the charge rate fell away quite quickly so we know for sure that this hasn't been charging whilst driving there are two more tests I need to do before I condemn the alternator and that's checked the fault drop across
(01:53) the positive side of our alternator circuit and across the negative side of our alternator circuit and I'm going to do that with my voltmeter I've connected my multimeter from positive terminal of the battery to the positive terminal of the alternator and I'm going to run the engine and put the headlights on and load the circuit up and I'm going to see if we get any voltage drop across that circuit I'm now going to carry out the same volt drop test for the negative side of the circuit so that's from the negative
(02:19) terminal of the battery to the body of the alternator, headlights on, so both Vault drop checks tested out okay, so that confirms it's our alternator. So we need to remove and replace the alternator, generally replacing an alternator on a VW Beetle would be an engine out job but I'm going to show you how to do it in situ so the first thing we need to do is undo the 36 mil nut on the back of the fan housing and we get down there with our deep rich 36 mil and a medium-sized knuckle bar and then we need to hold the front of
(03:05) the alternator pulley with the correct tool so take our 36mm on our knuckle bar we're going to put that down behind the fan housing and put it on the nut on the back of the alternator like so take our special tool so this actually sits onto the pulley and then we get good leverage and actually stop the pulley moving don't be tempted to put a screwdriver in here because it will just damage the edge and then you won't be able to undo it this tool does both six volt and 12 volt so it's a must if you're an air-cooled VW
(03:40) owner I can hold the pulley in the face while I undo the nut on the back of the alternator it's quite tight but it does go good that's it moved now I can put the ratchet in there it's a bit shorter now I've cracked it off and then we can undo our nut on the back so the first thing we take off is the nut there's also shims and washers on there so we must be careful that we take them off and put them back in the right order so using the 21mm socket in our knuckle bar and again are fan pulley holding tool you can hold
(04:25) that nice and tight and I can undo the front remove this 21mm nut and again we have to be careful because we've got shims and a washer here we don't want to drop those and lose those again important to remember what sequence they come off of so we can build it back how it was unless we're putting the new belt back obviously next we can remove the air filter so there's one screw under here on the clamp and then the other screw over here on the duct tin so I'm gonna pop a little bit of tape over the top of the carburettor just so we
(05:11) don't drop anything inside it or get any dirt in there it's going to move the wiring out the way obviously be very gentle and careful it's quite old the wiring we don't want to start breaking it next we're just going to pop the HT leads out of their clips off of the fan housing so that's out of the way that one there [Music] so the next part which is quite tricky is to remove the fan housing bolts so there's four bolts that hold the alternator to the fan housing two at the top and two at the bottom as long as the
(05:46) actual bolt heads as in 10mm bolt heads you can access those and there's obviously a bolt either side on the fan housing too so we can loosen the fan housing and the clamp that goes around the alternator and the pedestal and then we can get that all moving and we should be able to withdraw our alternator so I'll get that done to gain access to our last bolt which holds our fan housing together I'm going to remove the carburetor and that'll give us enough room to get down the bag yeah you hear you
(06:28) we can now gently wiggle the carburetor off it's good and it hasn't actually torn the gasket either so that's good news so now I can access that last Bolt down the back here a little bit tricky see without it's much easier it's got him loose before we go too far I'm just going to put a bit of tape over our Inlet manifold so again we don't drop anything down there tape across there because the last thing I want to do is drop That bolt that I'm removing straight down the inlet manifold and if I don't cover it up it
(07:08) will happen so let's see if I can finger that out yeah not quite so now with our last bolt out at the bottom I should be able to wiggle our alternator out so we've got our fan housing that's loose and obviously the cowl in Partners room is undone immediately pull it back also we need to remember that we need to pull off the actual fan from the other side we unbolt it lift that off oh there we go so now I just gently lift that out watch the wiring and there we go still with our shims this size as well so obviously be careful when you remove
(07:46) because we've got shims go there between that and the fan the fan stays in there now and then we can fit our new alternator to our fan cover here and refit it so we've got our old unit here I'm going to remove the dry flange off the back as you see I've got a three-legged puller here that I'm just literally using my fingers actually to turn the pillar to to pull it off it's on a straight shaft with a woodruff key, it's a fairly easy as long as it's not corroded on there that's good pull the rest of that off yep so we need to swap that over onto
(08:19) our new unit uh check that the space is the same and take the Wood Rough key out also so with my little toffee hammer and a small screwdriver should be able to just tap that woodruff key out so good I need to do the same on the front as well we're going to make sure we can get that Woodruff key out here well for the spacer and then we just check the spaces on the new unit we've got to make sure that they're the same depth with our woodruff key in position we're gonna slide on our dry flange like so, lovely,
(09:11) now we just need to put our spacer and woodruff key on the other side so we pop our original spacer back on and then put our little woodruff key and ready to put the belt drive back on that's it so before I put the New Year back on I've got our flats located on the fan horizontal and the same on the actual drive flange but also I need to remember to put on our original shins so I'm going to do that now so our original shims are going to go on we may need to change this but we're going to start where we left off
(09:46) bolt it all up together and make sure that our fan doesn't touch our fan housing so that's our three shims on we should be able to slide that gently into position so the bottom goes in first and then I'm going to have to lift the fan onto the alternator from the other side so our new alternator is bolted onto the fan housing with its four bolts the two at the top and the two at the bottom it's resting on the pedestal also I've put the fan on the back and I've put the fan nut on the back to secure it put the front pulley on so I could
(10:20) tighten the rear fan nut up which I've done and at this point we just want to make sure that when we spin our alternator our fan doesn't touch our fan housing so let's try that beautiful so we've got our clearance we've used our original shimming and it's worked out right if you are replacing your alternator and you find that you're just starting to scuff the fan housing you might want to add a shim or take a shim off so at this point you'd need to take it off and do that again but we can forge ahead now and get
(10:49) the whole thing back together, so just about to refit the carburettor um this gasket on the bottom of the base of the carburetor came off clean and good and hadn't broken away from the carburettor so I'm happy to put that back on I've just put a little tiny bit of grease on the surface just to help settle it back in if you did damage your gasket obviously make sure you change that gasket last thing you want to be doing is drawing air between the inlet manifold and the carburetor because it will just will not run right at all so
(11:38) back in place, we can get that all bolted up, so there we have it. There's how to replace an alternator on a 1970 Beetle without taking the engine in. For more hints and tips, follow us on YouTube, Facebook and Instagram and don't forget to check us out at justkampers.com. Thanks for watching.
