Tach doesnt work.

[weetee]

I just bought Sea ray, 1990 merc 115, and the tach isnt working. All fuse are good, wiring looks ok. Bad rectifier? Could it be something else? Would running it with a bad rectifier damage other electrical components?
Thanks.

 

[j_martin]

Re: Tach doesnt work.

It's hard on a battery to be discharged and recharged, especially if it's getting mechanically abused at the same time.

$2.50, and a little messing around and the problem is permanently fixed.

check this link:

http://forums.iboats.com/showthread.php?t=221719

 

[hkeiner]

Re: Tach doesnt work.

The tack may not be working because either the gauge in the dash is faulty, the rectifier/voltage regulator on the motor is faulty, or the wiring is faulty. You can use a voltmeter to check the voltage at the SEND terminal on the gauge to see if it is getting juice when the motor is running. If it is, then your gauge is probably faulty. If not, then check the wiring and the TACH output from the voltage regulator to see what is faulty.

The below link to the Teleflex troubleshooting guide provides more in depth help.

http://ww2.tflx.com/PDF/99320.pdf

 

[Chris1956]

Re: Tach doesnt work.

Weetee, The tach signal is the AC voltage from the stator. If your rectifier is bad, the tach should still work, unless the rectifier is shorted to ground.

First check to assure the tach has +12V, ground and an AC voltage to the sender terminal. If it does, the tach is likely bad.

 

[j_martin]

Re: Tach doesnt work.

Weetee, The tach signal is the AC voltage from the stator. If your rectifier is bad, the tach should still work, unless the rectifier is shorted to ground.

First check to assure the tach has +12V, ground and an AC voltage to the sender terminal. If it does, the tach is likely bad.

Most of the time the rectifier shorts to ground.

 

[MercFan]

Re: Tach doesnt work.

In my experience it's probably a blown tach. I've blown 2 already
I don't know about newer engine like the 1990s, but from the sound of it, it has a stator and rectifier, and your battery has to absorb the additional voltage at high RPM. I've measure mine at over 16V at WOT. I've even installed a second battery in parallel to try to tame the runaway voltage, but to no avail.

What I did then was install a standard automotive volt gauge. A 3 postion switch, and 2 automotive fog/spot lights below my dash. As soon as the voltage reading hits 14V I flick the 3 position switch to one side, which lights up one of the 2 fog lights. If my batteries are really charged 2 much due to over night on the charger, I sometimes even flick the switch to the other side and light up both fog lights and check the Volt reading.

Very crude but effective manual voltage regulator till I can find a decent one somewhere.

The whole thing sorts itself out when the batteries run down a bit. Then I can leave the lights off, and the voltage doesn't go over 14V as the batteries then have a bit of room for the extra juice from the stator at high rpm.

 

[campion165]

Re: Tach doesnt work.

i pulled my hair out with a tach not working try runnuing the tach off of the motor mine ended up being a bad connection coming off of the control box where the throttle is wiggle the connector while running have a brand new tach quicksilver when i bought one i did not need

 

[hkeiner]

Re: Tach doesnt work.

You can use a voltmeter to check the voltage at the SEND terminal on the gauge to see if it is getting juice when the motor is running. If it is, then your gauge is probably faulty.

Did you test for AC voltage at the SEND terminal before replacing the gauge? I am curious if this test was less conclusive at troubleshooting your tach problem than I would have expected.