hafe wave bridge question

[MH Hawker]

Friday I started having problem with my stereo shutting down at low rpm or when you drop it off of plain or when you start the motor, it works fine at WOT or sitting with out the motor running. When out today and went over all ot the connection and grounds. Hooked up a volt meter at the accessory buss to look and see what it was doing and had these results, just sitting 12.5 when I start the motor it has a very odd reading at idle it jumps all over the place and makes the meter reading blink on and off, at WOT its reading 14.2. I am wondering if the didoes in the bridge are breaking down and its throwing some ac back.

 

[wingless]

Re: hafe wave bridge question

It is normal for a voltage buss to have a lower voltage when the engine is off (~12.5) and a higher voltage when the engine is running (~13.8V). The alternator on the running engine is charging the battery, raising the voltage.

It is abnormal to have the voltage "jumping all over the place". Even if there was a problem w/ diodes or another problem, the battery will "smooth out" any fluctuations.

The jumping sounds like a poor connection.

 

[MH Hawker]

Re: hafe wave bridge question

I would have to agree. And why I went over the connection points, ever thing was rewired last year, but thinking about it the only thing I didn't replace is a 50 amp breaker where it branches off to the acc circuit from the perko switch. I will replace that tomorrow.

 

[bruceb58]

Re: hafe wave bridge question

I am wondering if the didoes in the bridge are breaking down and its throwing some ac back.

So put your meter on AC and tell us what you read. Should be less than 500 mV.

What you are seeing sounds more like a flakey regulator than a diode problem but its an easy thing to check.

 

[MH Hawker]

Re: hafe wave bridge question

Well Bruce, thats the thing its a small 9.9 motor and it doesn't have a regulator just a stator winding and a bridge, it a low charging rate ( 6 amps ) I can test the voltage with it unhooked from the battery because no regulator and will later today, I should of yesterday but I just got tired of messing with it.

This morning I was able to find a maxi type in line fuse holder and fuse rated at 30 amps and 10 GA wire and while its a bit under sized it will work for testing and presently the system draw is 20 max. I have a 50 amp /8 GA on order. I am going to replace the old 50 amp breaker thats in place now I believe its original to the boat (1988) and one of the few things I didn't replaced when I rewired last year, main wiring is 6 GA with the 50 amp breaker.

My plan is to test it in sections. I still believe its a lose connection and could be the contacts inside of the breaker and no I didnt test it, by that time I was frustrated with it and went swimming to cool off . I will start with that and if doesn't cure it than I will do some voltage tests.

The system components are the stator, bridge, perko switch, battery and a 50 amp breaker. I went over the visible connections yesterday.

 

[bruceb58]

Re: hafe wave bridge question

I see what you are dealing with. Does sound like a loose connection.

 

[bruceb58]

Re: hafe wave bridge question

As a quick test of the rectifier...

Disconnect the charging lead from the engine to the battery

Set your multi-meter to Ohms

Connect the charging wire to one lead of the multi-meter and the other to engine ground

Note the reading and then switch the leads.

In one direction you should have very low continuity and in the other a very high continuity.

Depends on the meter. Most higher end meters are made to not be able to forward bias a diode so you would see the same reading(open) in both directions. Higher end meters will have a diode tester to see what the forward voltage is.

Easier to just measure the ripple voltage with the AC setting of the meter. A bad diode will give you a huge ripple voltage.

 

[MH Hawker]

Re: hafe wave bridge question

Thanks, Bruce and Bubba I will try those suggestions. My meter dose have a diode setting and I did test the bridge while I was polishing the terminals and it showed good, but its a cheep meter, my good greenlee meter got stolen from work while I was in the hospital a few years ago and I ended up retiring so I never replaced it.

 

[MH Hawker]

Re: hafe wave bridge question

I got out to the boat tonight to do some fishing and I replaced the 50 A breaker with a 30 A fuse. I tested the impedance of the breaker and it was .01 so its not the problem. And while I was at it I tested the perko switch and it was also .01. With the motor positive lead disconnected and running at idle it still has the erratic voltage and it wouldn't read AC or DC it just jumps all over. So that isolates it to the motor. Being as it stabilizes at WOT to 14 VDC I would think at the very least the stator has output so I am back to the bridge and thinking about it I tested it as a hafe wave and it may very well be a full wave. I will see if my local dealer has one its not expensive. Its merc part no # 816770. I will dig a bit deeper into it tomorrow.

 

[bruceb58]

Re: hafe wave bridge question

You are doing all this measuring with the battery connected to its output right? If not, you need to have it connected. You need a load on the circuit.

 

[MH Hawker]

Re: hafe wave bridge question

Yes Bruce I have been, and its fixed, I spent a bit of time today reading in the manual on the charging system and it is a full wave bridge. So I picked up a new one and changed it out. That fixed it and the funny thing is the old one also tests fine but didn't work right. While its sort of WAG my thought is when running at WOT the voltage was enough to make it work but as the voltage dropped off it hit a fail point on one of the diodes and was jumping back and forth between good and bad and that was causing the wild volt readings, and it just hadnt completly failed yet. I may take it to a friend of mine and put it on a scope.

 

[bruceb58]

Re: hafe wave bridge question

I may take it to a friend of mine and put it on a scope.

Yes, that would be interesting to see.

 

[MH Hawker]

Re: hafe wave bridge question

Well honestly right now I am just glad to have it fixed. its been very trying lately I also had the CDI switch box go out later in the same day this problem also started :facepalm: