[fiskee]

I have a 1996 Jetta 2.0L (ABA) manual transmission. I've been having some frustrating problems with my coolant/ac system, but now the engine won’t start at all... I found out that the coolant fan wasn't working, so I replaced it (I found this out by (a) seeing that the motor electrical connection terminal was partly melted/blackened (b) measuring a very high resistance across the terminals (~100 Kohm) and (c) attaching wires directly to the motor from the battery and seeing no fan movement).

After replacing it I tried to test it out. After I started the car, I turned on the ac button (and air blower dial) from inside the car. I figured this would cause the radiator fan to turn on. Nothing. After turning the engine off and back on a few times, still nothing, but I noticed the ac clutch was not engaging. So then, I let the car warm up. After it got up to temp, still no radiator fan (maybe it still wasn’t hot enough). The next thing I was going to do was check if the wires going to the fan were supplying 12v (and if not jump the terminal on the temp sensor in the side of the radiator).

Anyways, now the fan is the least of my worries. Now when I try to start the thing it doesn't start. As I crank the engine over, every 3 seconds or so it sounds like one of the cylinders catches (semi-loud bang sound and a brief puff coming out the exhaust tailpipe), but it never starts - it just makes that sound every 3 seconds or so.

One thing I remember happening right before the car stopped starting: The repair book says to put the key in the ignition before reconnecting the negative battery terminal. I put the key in and turned it one click (the position where the radio turns on). After reconnecting the battery, I heard an electrical humming sound from inside the engine compartment. After removing the key from the ignition, the sound went away. A few minutes before that I had done the same thing to disconnect/reconnect the battery, and had never heard that sound. Then the car wouldn’t start. Not sure what it was or if it matters. Maybe the ignition switch was not in the correct position.

Not sure if this is at all relevant, but right before the fan problem I replaced a leaky plastic flange connected to the side of the engine which housed the coolant temperature sensors. I noticed the car wouldn't start with the sensor electrical connection removed (not surprisingly, it just kept turning over and over). So after encountering this new engine starting problem, I tried to start it with this temp sensor disconnected. When I tried this, the engine wouldn't catch (as expected), and there wasn't that intermittent (~3 sec) bang sound. I plugged the temp sensor back in, and the 3 sec bang sound comes back.

I would really appreciate any help – I have no idea what this latest problem is, but I do know the more “repairs” I do the more problems I seem to end up with… :-/