stator or rectifier for charging problems?

[okeyo]

74 merc 1150 wont keep battery charged.<br />is this likely the rectifier, or the more difficult to change stator?<br />can they be tested while on the motor, or do they need to be removed and/or disconnected to test?<br />thanks

 

[Laddies]

Re: stator or rectifier for charging problems?

Simply ring test the 2 yellow wire from the alternator if you have a complete circurt from one to the other the stator should work

 

[Laotzu]

Re: stator or rectifier for charging problems?

Some other possible problems...dead cell in battery, dirty battery posts, battery needs water. Best to put a voltmeter on the battery when running. Should be 14.5V or so if regulated. If so, the battery may be bad. If not, then either stator or rectifier as you suspect.<br /><br />Jerry

 

[okeyo]

Re: stator or rectifier for charging problems?

by "ring test" do you mean using an ohm meter? what setting should the ohm meter be on?<br /><br />should voltage at the battery be tested at idle or at a certain rpm? the other day i checked it at 1500 rpm and it was 11.98

 

[wilde1j]

Re: stator or rectifier for charging problems?

A fully charged battery at rest (after waiting at least 20 min. from any charging) should read 12.68 vdc. Your battery, assuming the wiring is OK, isn't being charged.

 

[achris]

Re: stator or rectifier for charging problems?

'Ring test', yes I'd never heard it described as that either. I think he means ohms test, and set the meter to ohms X1. You should only see a few ohms on the stator. The rectifier is just 4 diodes in a bridge format. Usually the fault is the rectifier, but not always. Usually the rectifer is killed by connecting a battery the wrong way round. There is no time limit on this, the damage is immediate. <br /><br />Good luck,<br /><br />Chris................

 

[bdallam]

Re: stator or rectifier for charging problems?

I also seem to have a charging cicuit problem. My daughter called in for a tow back to town with dead batteries, (she was running on both and stopping and starting the '87 150 XR2 a lot to pick up and drop off skiers and tubers). The rectifier tested bad so I replaced it. Starts and runs fine, but no guages or tach. So I replaced the stator as well. The new stator made no difference. I have continuity from the positive post on the rectifier to the positive post on the tach with the key switch turned all the way over to "start", but not with the key switch in the "run" position. To complicate matters this engine has a two post voltage regulator mounted on top between the heads. My Seloc manual makes no mention of this voltage regulator, and I have no idea how to test it. It shows 20.30 ohms across the terminals. I tested one on another '87 150 and it showed 20.05 ohms. Anyone know how to test this thing, or what the resitence value should be?<br />Any ideas? Right now I'm thinking the voltage regulator is bad, or maybe the key switch? My seloc manual says to test the charging circuit by using a special adaptor to allow a VOM type ohm meter to read the positive battery conection. I don't have this special adaptor or a VOM meter which could stand the starting amps of the circuit using it directly. My amp probe reads 2.5 amps at low idle and about 5.5 amps at high idle. this seems low, although it may not be accurate as the amp probe is designed to read AC not DC. BD

 

[achris]

Re: stator or rectifier for charging problems?

BD,<br /><br />1. Bin the Seloc manual and get yourself the proper Mrec genuine manual. <br /><br />2. You can't measure DC current with an AC meter. Doesn't work. Results are meaningless.<br /><br />3. Resistance testing the voltage regulator is totally irrelevant and meanless. <br /><br />4. Continuity from recifier to post on tacho is also irrevevant because you would be going through the regulator. Test from positive post on the battery (or the output terminal on the regulator) to the post on the tacho, with the negative battery terminal removed of course!<br /><br />Do you have a variable power supply? If so, connect up the regulator and check that it is regulating at 14 volts (or very close to that). If not, Disconnect the regulators and run the system 'unregulated', the output voltage should rise quite rapidly, Don't let it get over 17 volts. If it gets up quite quickly, the regulator(s) are toast. <br /><br /><br />Good luck.<br /><br />Chris.................

 

[bdallam]

Re: stator or rectifier for charging problems?

Cris, thanks. I don't have a variable power supply, but I'll recheck the continuity to the tach post as you suggested. BD

 

[bdallam]

Re: stator or rectifier for charging problems?

Chris, two points, first the rectifier positive post and the regulator positive post are directly connected. I have a two post voltage regulator which is grounded to the block through it's mounting. The pos (red) wire from the regulator goes to the positive terminal on the rectifier and the yellow wire from the regulator goes to the alternator post on the rectifier. The wiring diagram shows the positive post on the rectifier as being the source of DC current through the key switch to the tach with a grey wire from the sending post on the rectifier going directly to the tach with the signal. I have no idea how this type of volyage regulator works as it is not "in line" to the rectifier, but sort of in series to one half of the rectifier. I'm going to borrow a VOM meter this morning and gather some more info. If I can borrow a variable voltage source I'll try testing the regulator as you suggested. The Seloc book talks about the combo regulator/rectifier units on the newer motors as providing charging current for the battery as well as regulated current of about five volts for the instruments to prevent the instrument readings from varying with rpm. Seems like my earlier set up might be designed to accomplish the same goals with different components.<br />BD

 

[achris]

Re: stator or rectifier for charging problems?

BD,<br /><br />Sorry about the mis-info. I haven't been able to check the wiring diagram for your enigne as I'm not at home. <br /><br />The regulator is indeed in parallel with the rectifier, it dumps excess voltage (as heat) into the water at the top of the block. <br /><br />If you had continuity with the key in the 'start' position but not in the 'run' position, then you almost certainly have a faulty key switch.<br /><br />Chris................

 

[bdallam]

Re: stator or rectifier for charging problems?

Problem solved, It wasn't the key switch, but the rubber five wire connector to the dash wiring. I had unplugged it in the course of looking for the problem and it just wouldn't make a good connection after that. I eventually found it by checking continuity from the engine conections forward, one wire at a time, a long and tedius process. My initial replacement of the rectifier fixed the charging problem but the faulty plug prevented the tach and temp guages from registering the fix. For future reference; The battery should show 12 + volts with the engine off, and near 15 volts running WOT. The grey wire from the rectifier should have continuity between it's conection on the rectifier and it's post on the tach at all times, and should show 5+ volts when running. The positive terminal on the rectifier should have continuity to the positive post on the tach with the switch on. With the key turned to start it will always show continuity as it is feed back from the starter solinoid through the red wire with the 20 amp in line fuse as well as through the key switch. The voltage regulator check on this model is the reading on the gray wire: with a bad regulator, the voltage will vary through the grey wire with rpm. A good voltage regulator holds the reading to 5+ volts regardless of rpm. Thanks for all the help. BD