Loss Of Tach After Battery Change

jcdargas

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Sep 9, 2003
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I have a '99 Bennington pontoon with a '99 Evinrude 90. Recently the OEM battery played out and I had to put in a new one. Ever since I installed it the tach's been stone dead. <br /><br />I can find no loose wires either on the tach or on the motor. There appears to be no fuse in line. It was a "clean" install; no sparks flying when hooking up the cables.....<br /><br />Am I looking at a rectifier problem?
 

Xcusme

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Apr 21, 2003
Messages
2,888
Re: Loss Of Tach After Battery Change

Could be a rectifier...is the motor charging the battery?? What's your battery voltage while running??
 

jcdargas

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Sep 9, 2003
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Re: Loss Of Tach After Battery Change

The battery appears to be charging and the motor runs smoothly. I'm running about 12.9 volts running. Have run as high as 13.9. The last time I went out I had charged the battery up before going out with a "Guest" on board charger and only really ran for about 30 minutes to the fishing area and back.... Could have been running on the deep cycle charge, I can't really say....<br /><br />It did this intermittently right after I bought it (new) but first service took care of it and it hasn't done it since until now. The original problem wasn't causing it to be completely dead, just sporadically shutting off... :confused:
 

Xcusme

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Apr 21, 2003
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Re: Loss Of Tach After Battery Change

I guess the most important thing to ask is, Does the voltage go up or down with RPM's.? Is the voltage output higher at higher RPM's?? The voltage at idle of 12.9 should be higher. Keep us posted...
 

jcdargas

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Re: Loss Of Tach After Battery Change

I probably beat around the bush on my response... Actually, I don't know if the thing is charging. I was getting the 12.9 off of my fish finder and it wasn't fluctuating like it normally does.<br /><br />I'm going to hook up a hose tomorrow and check the ammeter to see if it's showing any movement other than dropping.<br /><br />The reason that I'm not certain is that I didn't really pay any attention to che charge rate because I was out on the lake before I found this website and encountered someone willing to assist.... Had I been here before Monday I'd have had all the answers at this time.<br /><br />Watch this spot for further developments, and thanks for your interest and help.
 

roscoe

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Oct 30, 2002
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21,750
Re: Loss Of Tach After Battery Change

If you accidentally touched the battery cables to the wrong terminals, even for a second, you may have fried the rectifier. The rectifier feeds juice to the tach.
 

jcdargas

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Sep 9, 2003
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Re: Loss Of Tach After Battery Change

I was extremely careful about not doing that. Having purchased two rectifiers one weekend about 15 years ago I learned that lesson. However, I would imagine even a moderate surge from almost anything electrical could have fried the sucker. Am I right???
 

Hooty

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Oct 2, 2001
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Re: Loss Of Tach After Battery Change

When you hooked the new battery up, which terminal did you hook to first, neg. or pos.?<br /><br />c/6<br />Hooty
 

Hooty

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Oct 2, 2001
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4,496
Re: Loss Of Tach After Battery Change

Oops. That could zap the rectifier. I'm not saying it did but you should hook the pos. cable up first and the neg. last.<br /><br />c/6<br />Hooty
 

jcdargas

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Sep 9, 2003
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Re: Loss Of Tach After Battery Change

Thanks a bunch. That's probably my problem. Got any idea how a bad rectifier reads on a volt/ohm meter???
 

Solittle

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Apr 28, 2002
Messages
7,518
Re: Loss Of Tach After Battery Change

Put a volt meter on the bat & record the voltage. Start it up and take another reading. You should pick up about a volt or so if all is OK.
 

kd6nem

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Jul 25, 2003
Messages
576
Re: Loss Of Tach After Battery Change

Hooty: WHY would changing one terminal first make a difference? A circuit is a circuit, and it "either is or it ain't". And the circuit is made and broken every time we turn the key on or and off. If you know something I don't I reckon it is time I learned it. So long as the load is in the middle where it belongs I can't see why it'd make any difference. <br />I'm not trying to argue, but am curious as to the reasoning.
 

Hooty

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Re: Loss Of Tach After Battery Change

I think it has to do with the polorized, solid state DC devices.<br /><br />c/6<br />Hooty
 

kd6nem

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Jul 25, 2003
Messages
576
Re: Loss Of Tach After Battery Change

Well, I wonder if this idea might have come from the safe way to jumpstart a vehicle? Connect/disconnect ground (FRAME, not battery terminal) last to keep from sparking near the battery because of the hydrogen gas coming from the battery? Now that is a wise notion, since there will be a big spark when that arraingment is made. Explosions and fire tend to ruin the outing. You got me thinking- it would be a good idea to make sure all the load is turned off before the connect/disconnect to minimize sparks- turn the battery switch off is the easiest way.<br /><br />I've dabbled seriously with electronics for years and have never otherwise seen a reason to favor one side over the other. Polarization of some devices is true enough (like rectifiers, transistors, some capacitors, IC's), but shouldn't otherwise make a difference which cable is first disconnected so long as they are not cross connected, as was pointed out. Doggone if I didn't go and prove that true myself a couple years back. Sure does pay to pay attention, doesn't it! I bet at least half of us have gone and done that, or are JC and I the only ones going to fess up? ;)
 

rodbolt

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Sep 1, 2003
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20,066
Re: Loss Of Tach After Battery Change

hahahaha<br /> I am laughing my rumpus off. I have "bought" my fair share of electronics along the way. I was an FC in the navy. we had a saying that if you had not fried at least 1/4 million $$ worth of circuit cards then you were not a "real" tech.<br /> keep looking but by all means buy the servive manual. does your engine have the regulator rectifier mounted under the flywheel or is it the old 3 wire rectifier mounted on the stbd side of the block? remember to make it work. Keep the smoke in the wire and the rest is PFM (Pure Freeking Magic)
 

jcdargas

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Sep 9, 2003
Messages
18
Re: Loss Of Tach After Battery Change

Guys, this has been a real expeerience. I really appreciate everyone's input. I'm going out and pull the cover on the motor as soon as it stops raining and check to see if I can locate the rectifier. I can probably pick one up today before noon. I'll let you know what happens.<br /><br />Rodbolt, it may not stop raining where you are for a while... Do me a favor and do some kind of dance to ward off the 'cane headed our way. I'm going to be at Corolla the second week of next month and I'd really like to have a roof over my head and the place we've rented is right on the beach.... Hope you're giving serious consideration to bailing out of there....
 

rickdb1boat

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Jan 23, 2002
Messages
11,195
Re: Loss Of Tach After Battery Change

rectifier.jpg
 

jcdargas

Cadet
Joined
Sep 9, 2003
Messages
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Re: Loss Of Tach After Battery Change

Rick,<br /><br />I just printed out the test instructions you sent. I'm going to stick them in my "boat papers" file for future reference. I really appreciate that. That will take the guesswork, not to mention unnecessary bucks, out of the project. Not only that, it'll sure save me a bunch of time and trouble uncovering the boat, towing it 20 miles down the road to Wake Forest and reversing that to pick it up after paying an excessive repair bill....<br /><br />Hopefully, this will be the problem. This one I can do without much sweat.... ;)
 

jcdargas

Cadet
Joined
Sep 9, 2003
Messages
18
Re: Loss Of Tach After Battery Change

Guys,<br /><br />Thanks for all the help. I do have a bad rectifier. It looks like it's going to be a major pain in the butt to replace but I guess I'll give it a shot.<br /><br />Thanks a bunch, again. Hopefully, (unrealistically) I won't have any more problems with this thing for a while.<br /><br />Hope nobody gets blown away with the 'cane. :D
 
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