Ok so here is the deal. I recently put a diesel tach in my scirocco. I searched the shop and found an alternator that had the W terminal and installed it. Success! The tach works. I drove it home last night and everything was great (except for the intermittent cutting out of the engine, but thats another story).
I went to the store today and it worked great for about a block. No I have no tach
The alternator light is not on, everything seems to be working as normally as before I put the alternator in. I checked the connections and they seem fine. I might also point out that right before it died, it was reading really low (about 2k rpm lower than actual). Then it just stopped working all together. I tapped the cluster and nothing changed.
any ideas? Can this be fixed by tearing the alternator down and inspecting connections? Is there a common problem in the alternator that I should look at?
Thanks!
Tighten the belt first.
Mine would only go to 1K and sit there. I found a bolt missing from the A/C compressor. Replaced bolt, tightened belt works great now.
Yeah.... don't trust the idiot lite to tell you the alternator has a problem... I'd suggest getting a voltmeter on it just to make sure it really is working.
Should be 13.5ish volts when running... no alternator, no tach signal.
Assuming your alternator is giving you a good output, and the wiring is all good, then all that's left is the cluster.
Well the belt is tight. I dont have my meter here, its at the shop and thats about 20 miles away. I can check it tomorrow when I get to work.
I doubt its in the cluster as I have gone through that thing like you wouldnt beleive. Its actually an early MKII Scirocco cluster with MFA and the tach from an '85 TD Jetta and the speedo is original to the car ('87 Scirocco 16v).
Has anyone seen just the W terminal part of the alternator break and the rest of it work fine?
Oh yeah, doesnt have AC so one belt just for the alternator and waterpump. PS is still there but thats a separate deal.
It appears to have fixed itself. About 5 miles into my commute, it started working in the exact same sequence that it died. :?:
Ok somewhat of an update:
I have been having this dying problem that displays itself when hitting bumps. Checked all the connections and they seemed ok (ip shut-off solenoid). I found that if I pushed in the clutch, the car would return to idle and I could rev it up, put it back in gear and all was good until I hit the next bump.
I think I may have found the cure to both problems tonight on my way home. Car was dying (return to idle) at almost every little bump. Tach was working as the engine was warmed up. I pulled off the freeway at a gas station to see if I could wiggle the connections and have good contact. In my investigating, I found that everything was tight except for the positive battery connection. Almost all the connectors were new and crimped properly. The connection wasnt super loose, just slightly. When I checked it the lights and everything were on and the small leads (not the starter lead) were hot to the touch. I didnt have a 10mm wrench or anything so I MacGyver tightened it all and the car didnt cut out all the way home (I had travelled 8 miles and needed to go another 10 miles).
So here is my theory (let me know if it doesnt make sense):
At higher RPM the alternator is charging the battery with more Amperage. Slightly different than an FI gasser as I dont need electronics to run my engine or an electric fuel pump. Poor alternator B+ lead to the battery was causing high resistance due to poor connection. Somehow this affected the W terminal input to the Tach. This also caused my cutting out problem.
I guess I will know for sure tomorrow if the tach works right away. I suspect maybe the glow plugs drawing too much current on startup might affect the connection on the B+ terminal when cold and the tach works better after it has come to some sort of equilibruim with the battery.
p.s. Battery is new 41 series Interstate.
slight update:
tightening the positive battery cable wires fixed the dieing problem, but did not fix the tach problem. I will delve into the alternator at a later date. Most likely, I will replace the alternator with a TD MKII style along with the bracket as my power steering does not have the upper support. I have the early diesel cast iron bracket right now.