[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
On 7 Oct 2003 at 2:11, Mike Wodkowski wrote: > Now the light's going on. > > At fuse, ignition OFF: 12V > > Engine Running: 12V, Sped Up Idle: 12V > > As per Bentley, Disconnect DF and D+ wire at Gen,, ran a wire D+ to ground > showed about 2V, when then connect a wire DF to Gnd, jumped to about 25, > both readings engine at idle. Weird because Bentley said this should read > around 12V and then jump to 36 when the idle was revved. Confusing. I don't think you've written this down right. There would be no reason to want to short D+ to ground, and if you did so, how could you still get 2V there? The Bentley test is the same as mine. Both are illustrated in fig. 6-4. > Using Jim Adney method, DF disconnected, VOM running from D+ to GND and a > wore running briefly from DF to gnd, I got no sign of fluctuation at all on > a reading of about 2V. And no change with acceleration. > > With both wires connected, VOM running D+ to GND, about 2V engine running. Okay, so apparently you already have my generator FAQ. Good. These are both good tests, and the results are consistent with the idiot light being on. There appears to be something wrong with the generator. Here are some things to check: 1) Make sure that the pigtail securing screws for both brushes are secure and that both brushes are free to slide in their holders, so they can get to the commutator. It's okay to reach in there carefully with the engine running and push down gently on the back end of each brush, just to make sure that the brush is making good contact. Sometimes this is an easy fix. The brushes should be long enough that their tail ends stick out the outside ends of the brush guide sleeves. 2) Make sure that when you installed the generator wires you didn't let the connection studs turn in the generator body. If you did, that could break off the wire soldered to its inside end. If you turn the generator just right you can look in there and check those wires to make sure they are still secured to the heads of those screws. If one of these is broken it can be fixed, but it means taking the generator out and some disassembly to resolder that connection. 3) Look in that same area to see where the various wires are passing. You may need to move one of them away from something that it is grounded against. Shorting to one of the long thru bolts that holds the generator together is a somewhat common problem, but this is easily fixed by just bending the wire slightly away from that thru bolt. Later rebuilds have a pink plastic sleeve over those bolts to prevent this problem. 4) It's hard to get to, to see, but check out the front (front is front) end of the generator. There are some venitlation holes in that end plate. There should be a small slotted head screw visible thru one of those holes. It is recessed about 3/8". This screw head will be near the top of the generator, as installed in the car, just inboard of the rightmost (D+) terminal. You should be able to feel it with your finger. If that screw has fallen out, the generator won't work. That screw is an M4 x 5mm screw, with a lockwasher. There's plenty of room inside to clear a longer screw if that's all you can find. 5) Make sure that you've installed the "new" generator correctly. If it's not sitting correctly in its "saddle" then it won't get proper cooling from below. See fig. 6-7 for the proper orientation. The dot on the strap must be lined up with the dash on the generator body. The dash does not show up well in that photo. If this was installed wrong, it's possible that the field coils or the armature has been cooked from lack of cooling; in this case, a properly installed rebuild is your only answer. > Bentley says to "disconnect" B51 lead, then hook VOM to b/51 and > ground, start engine and check reading... but with b/51 disconnected, I > cant start engine. I can't even key on, and I shouldn't be able to > according to the wiring diagram. Is this an error? That must be the B+ (51) wire. That wire was connected differently on various years, so it would work on some and not on others. I don't recommend this test anyway, because of the risk of shorting the B+ wire to ground, which would make a real mess. > The readings above are all Before AND after I put in a new set of > brushes, and a new VR just to be positive, since I had them lying > around. > > But no dice, its gotta be the new rebuilt generator, right? Possibly, but some of the generator problems are things you can fix cheaply yourself. -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org