'81 Rabbit convertible, Hall sender, testing/replacing questions

[pstallard]

I have an ’81 Rabbit convertible (gas). My brother was using it for a while a year or so ago, and it had a bad hesitation problem, which he managed to track down to the Hall effect switch. Two of the three little wires between the sender itself and the plug on the side of the distributor were losing their insulation and possibly shorting out, and the third was broken. He wasn’t able to find the part anywhere at the time, so he did his best to insulate the two wires and solder the third, and he fixed the problem.

Then last week the car suddenly started having similar (but not exactly the same) problems. Every time I took my foot off the gas it would immediately die. Basically it seemed that if I wasn’t actively accelerating, the engine would die. Otherwise it started and ran fine. We suspected that it was the Hall sender again, since my brother had always expected his temporary fix to fail at some point... So I pulled it, and sure enough it looked like his solder joint had failed (although it’s always possible I accidentally broke it while getting the unit out…). We re-did the repair, even had high hopes we’d done a better job than before, but when we put it back in the car it won’t even try to start now, and we’re getting no spark from the coil wire. So, questions:

We want to test to verify it is actually the Hall sender. The Haynes manual I have has different testing procedures for “All systems except CIS-E Motronic” and “CIS-E Motronic systems”. I’m not sure which we have. How can I tell?

The manual says to check the switching function of the Hall sender by using a “low voltage LED test light”. I need to buy one, and I want to make sure I’m getting the right thing. The local auto parts place has several but couldn’t tell me which is the right type to use for this. I really don’t want to test and think I’ve pinpointed the problem because I get no flickering light, when really I’m just using the wrong type of test light… Any advice on what to look for to make sure it’s the right type, and where to get one?

And the big one: I can’t find a source for a Hall sender module for this year and model anywhere! I’ve tried several auto parts stores, eBay, Amazon, general Google search… Nothing so far. I did find a couple that I thought might be right, but in the end I determined they weren’t compatible after all. Does anyone know a source for this part? The sooner I can get a new one the better, as this is my only vehicle at the moment, and I’m stuck taking buses until I can get it fixed.

Thanks!

[kamzcab86]

[pstallard]

Thanks kamzcab86, that's very helpful stuff!

I haven't done all the tests of the whole ignition system as recommended by the manual yet because I don't have a volt meter available right now, but I bought a two LED test light (package says "Computer safe automotive logic probe", "Current draws less than 7 milliamps" "Dual color LED indicates red for power and green for ground"...) and did the test in the manual for "Checking the operation of the Hall sender switching function":

- Removed coil wire from center of distributor, and grounded it
- Connected red lead of test light to positive battery terminal
- Connected black lead of test light to ground
- Peeled back the rubber connector boot, and held the probe on the center wire, while someone cranked over the starter

The green light was on through the whole process, the red light never came on at all. With the starter cranking, the green light showed a *very* slight flickering, really hardly at all. Do you think based on that it's safe to say that the Hall sender is bad?

As far as finding a new one goes, you're right, the parts number really helped a lot. I've found several sources. One question: How did you get the number for the part? I couldn't find a list of part numbers in the manual...