97 Challenger with strange rectifier/regulator behavior

[seeedooo]

Dear Seadoo enthusiasts,

I bought a used challenger about 2 months ago and am working on a view issues since then to get it to run properly. I am not very familiar with seadoo technology but have some hands on background dealing with 2-stroke engines.

Currently I am working on an issue with the rectifier/regulator (RR). I measured the voltage at about 5000rpm and it was rising over 15V and I read on the forum that that indicates that the RR is bad and needs to be replaced. Therefore I bought an used one (was told it had been tested) and installed it yesterday.

The first time I started the boat it showed the same behavior as with the old RR. First I thought that I received a faulty part or that something blew it right away. But when I let the engine running a little longer at 5000rpm and the voltage dropped to 14.2V and the RR seemed to be working properly. The thing is that from time to time the voltage increases slowly up to 16V as if the RR is defect but then suddenly drops to 14,2V again as though the RR is working fine.

My question is now what could explain this behavior and how I can analyze the cause of this and fix it. Is it correct to assume that the RR is intact? Wouldn't the voltage be over 15V permanently if I run on constant 5000rpm when the RR would be defect?

Could it be the stator? I measured the yellow cables against ground and they were all open. Is there any other measurements I can do to verify that the stator is intact? And again, does it make sense that the problems comes and goes when the stator would be faulty?

I thought that it might be bad ground between battery and motor? The only connection between battery and motor I could find goes to the starter. The cable and connectors look good. Could the behavior be explained with a bad ground connection?

The whole thing puzzles me a lot as it looks like the RR is working some times and sometimes not. Any help or suggestions are very much appreciated.

Thanks and kind regards
seeedooo

 

[Dr Honda]

was this a used regulator?? If it was... it's bad. (assuming the battery isn't shorted out)

16v can take out the MPEM. That's a $600 part, so be careful.

 

[seeedooo]

Hi Dr. Honda,

thanks for your answer.

Yes it was a used RR. My first thought also was that it is bad. But I was reassured that it was working and had been tested.

Could it be that something had taken it out right away after I built it into the boat and started it? Just want to minimize the risk that I would loose another one if I build in a new one and havent fixed the cause if the problem.

How can I find out whether the battery is shortened out or not? It shows a little more than 12V when I messure the voltage with motor turned off. When I run the motor for a while it shows about 13V after turning it off.

Thanks again for your help
seeedooo

 

[Biffitis]

Check your battery voltage after it's been sitting UNCHARGED for about 24 hours. If you're still around 12.5 volts then you won't have a shorted cell. One shorted cell will pull the voltage down to around 10.5v after a short period of time.

I agree, it sounds like a bad R/R. Either that, or a bad connection at the R/R. Most Regulators will compare ground (zero volts) to their target (14 volts). If you had a bad ground, or a bad sense voltage (what the voltage is actually at) then the Regulator can't function properly.

For example; the Regulator is comparing left (zero volts) to right (14 volts) and trying to keep the difference between the two uniform (14 volts). If right drops to 12 volts (because of a bad sense or connection) but the actual voltage in the system is still at 14 volts, the Regulator now only sees a 12 volt spread from left to right and increases the output by an additional 2 volts, which brings the actual system voltage to 16 volts now.
Basically, check all your charging system connections, power and grounds. Not just visually, but physically.