Tachometer not working!

[jpwilly]

Hello iBoat Force Forum! My name is Joel and I have a Force Outboard - :lol:

I have a new to me 1994 Bayliner Capri 1700LS with the Mercury Force 120 (serial # OE0493XX). Boat and Engine appear to have been built in 1993 sold as a 94. Tach / RPM gauge isn't working. When run power is off needle is straight down and when power is switched on the needle moves to zero. When cranking or running needle doesn't move off of zero.

I've looked behind the dash and checked the wires are all connected correctly and tight.
I've moved the arrow between the different settings and back to the #4 and checked to see if I have a 20pole or 12pole (it's 12).
I've removed the cowl and looked at the regulator / rectifier. Looks like an aftermarket unit with two yellow, one red, and one grey. All are connected up properly.
I don't know if I have a battery charging issue or not
I have the Black Stator not the newer Red one but it looks good no goo or burn marks.

Is there something I can hook up to the signal wire (other than my tach) to see if it's pulsing?
Or what other simple testing can I do to determine if I have a bad regulator / rectifier

I don't have a shop manual and figured I could download a free PDF somewhere but haven't found one. Anyone have a link or care to share?

Thanks for helping in advance - Best,

Joel

 

[Jiggz]

Re: Tachometer not working!

In your case, the gray wire is I believe to be the signal wire from the stator. Make sure it is properly connected to one of the yellow wires from the stator or from the input terminals of the rect/reg. Check for continuity also to make sure it is properly connected to the input terminal of the tach. As fro the tach needle dropping below the zero and "standing" up to zero when the ignition is turned on, that is perfectly normal since the ignition sw powers on/off the tach in the accessory position. This is to make sure it (tachometer) is not energized when engine is not running thus preventing battery drain. To test for positive power, test voltage (to ground) at the tach power terminal with the ig switch in the on position.

If you cannot verify the gray wire continuity, you can use a substitute wire with one end connected to one of the yellow wires and the other end to the tach signal input terminal. With the engine running the tach should indicate RPM. If not it could be the tach is already toast. But before jumping to that conclusion, double check the two yellow wires to make sure they have AC voltage on them with the engine running.

 

[jpwilly]

Re: Tachometer not working!

Thanks Jiggz I appreciate the help. The gray wire is connected to the gray wire from the wiring harness that is then connected to the signal on the Tach. I just checked the continuity with 2 harbor freight multimeters one at the engine one at the helm and the wire has continuity.
Gray wire is not connected to any yellow wires though. I pulled the reg and have posted a picture. The gray wire looks burnt...maybe that is a problem? The reg/rectifier must be grounded at the base because there is no black wire. There is a part number on the reg 817411 1 appears to be the stock unit not an aftermarket one.

 

[jpwilly]

Re: Tachometer not working!

Tried another thing. I have continuity on the gray wire so I connected it to the yellow AC lead from the stator and cranked the engine with the safety cutoff switch pulled so the motor wouldn't start...no RPM's registered while cranking on either yellow wire...bad tach?

 

[gm280]

Re: Tachometer not working!

Before trashing your tach, verify your rectifier is indeed working and charging your battery. The reason is that the tach can be not seeing any pulsing signal to operate on. If you can verify that you have a good working stator AND rectifier/regulator and you are indeed charging your battery and still not displaying any RPM's, then you could have a bad tach... But any issues with either the stator, rectifier or the regulator can effect the tach signal... JMHO!

 

[jpwilly]

Re: Tachometer not working!

gm280, I searched for a simple way to test the regulator / rectifier and you tube had a couple of videos.

Using my digital multimeter I used the diode test function and have verified the following. In one direction the red and one of the yellows don't read but in the other they do. BUT the other yellow AC input and gray tach signal wire read in both directions. I don't know if that is correct or not but seems it's not suppose to do that.

Is there anyone who knows the proper way to test the regulator with a multimeter?

 

[pnwboat]

Re: Tachometer not working!

Since there is a regulator circuit along with the rectifier, it may be kind of hard to check it conclusively with a meter with the diode test function.

Fire up the motor on muffs and get the motor up to 3000 RPMs and check for 14.5 volts D.C. on the red wire of the Regulator/Rectifier. Since your tach isn't working, you'll have to play it by ear, but it should be pretty obvious if it's not putting out the proper voltage. If it isn't, check the A.C. voltage from the stator on the two Yellow wires. It's usually around 16 VAC at 3000 RPMs. If it looks good, then replace the Regulator/Rectifier.

 

[Jiggz]

Re: Tachometer not working!

Looking from the pics, you can verify the connection of the gray wire with any of the two yellow wires doing continuity tests between the gray wire and any of the two yellow wires. At least one of them yellow wires should have continuity with the gray wire. If there is none, then the rec/reg could be toast. But then you can fully verify this by taking output readings from the rec/reg as mentioned by PNW. If output voltage is equal to or less than battery voltage, the rec/reg is toast or not working.

Another test would be to disconnect the two yellow wires from the rec/reg and then connect one of them to the gray wire and then run the engine on muffs and you should see RPM on the tach, if the tach is working. And if you read voltage between the two yellow wires at this point, there should be some AC Voltages which is usually around 16 VAC depending on RPM.

If there is AC Voltages from the two yellow wires, there is continuity within the gray wire (more or less 1 ohm total resistance) and there is positive power going to the tach (with proper negative or ground connection), but there is still no rpm indication, it is high time to uninstall the tach and do a bench test.

And yes, the rec/reg has grounded casing for the negative terminal.

 

[jpwilly]

Re: Tachometer not working!

Yes the gray wire and one of the yellow wires has continuity between them.

I'm going to run it on muffs later today and perform the test for AC voltage from stator and DC voltage from reg at mid RPM's and get back with the results.

 

[jpwilly]

Re: Tachometer not working!

Okay pushed the boat out of the garage and tested the AC voltage from the two yellow wires running from Stator. Set the multimeter to ACV 20, black comm leed on the base of reg and red wire connected to yellow wire the display read a pretty steady 18volts on my digital multimeter but was blinking in and out from the pulsing.

I changed the setting to DCV20 black comm on base of reg for ground and red leed to red wire output from regulator to battery was all over the place - it was pulsing not steady everywhere from single digits to double digits into 18's. all over the place.

Was I to test the DC voltage at the battery or on the Regulator?

 

[Jiggz]

Re: Tachometer not working!

It sounds like you read Vac from one yellow wire to ground. Instead it should be between the two yellow wires (i.e. black lead to one yellow wire while the red lead to the other yellow wire. And you should read at least 16 Vac depending on rpm ( and yes, because the RPM is not really steady, the voltage reading will be jumping within range of 14~18 VAC.

As for reading the DC voltage output of the rec/reg you did it correctly, but the reading should be pretty much within range of 13~14 Vdc. Technically this will indicate if the rec/reg is properly working and shouldn't have any bearing with the tach. But then, the gray is internally connected inside the rec/reg which means a shorted rec/reg can interfere with the tach input signal.

So the next step is to isolate the rec/reg by disconnecting the two yellow wires and then jumpering or connecting the gray wire to one of the yellow wires directly. A jumper with insulated alligator clips is perfect for this task. Before running the motor, double check the power going into the tach. Basically there are only three terminal connections behind the tach, i.e. signal, battery and ground. I use two jumper wires with alligator clips to connect the tach and voltmeter so as not to keep holding the leads while testing (unless you have a 2nd person who can turn on the ig sw while you hold the leads in place).Turn on the ignition sw in the run position, and there should be 12 volts DC between the battery and ground terminals. If there is none troubleshoot. If there is then go ahead and set up the motor for running with the 2 yellow wires disconnected (from rec/reg and one yellow wire directly jumpered to the gray signal wire going to the tach (NOT THE GRAY WIRE GOING TO THE REC/REG UNIT). With motor running, there should be RPM indication on the tach. If not, the tach is most likely toast.

Uninstall gage and do some bench testing or you can uninstall it and situate it close to the motor. Connect it directly to 12 VDC (battery) using jumper wires and another jumper wire straight to one of the yellow wires. If it still will not indicate RPM ,it is time to replace it. Usually, at the back of the gage, there are switches or settings to set tachs to appropriate number of pole settings make sure this is correctly set.

 

[jpwilly]

Re: Tachometer not working!

Ok I will try this again tonight. And read AC voltage from both wires this time, oops. I have tested for power at the TACH with power on and it's 12.68volts DC. I've tested continuity all the way back on the signal cable to so the wires are good. I'm pretty sure my rec/reg is bad but no point in replacing good parts. I especially don't care for electrical work but the more I learn the better off I'll be.

Thanks for the help so far iBoats members I'll keep going until this is fixed with your help.

 

[pnwboat]

Re: Tachometer not working!

I changed the setting to DCV20 black comm on base of reg for ground and red leed to red wire output from regulator to battery was all over the place - it was pulsing not steady everywhere from single digits to double digits into 18's. all over the place.

Was the red lead connected to the battery while you were checking? If so, then I would say that your Regulator/Rectifier is probably bad. It should be steady at approx. 14.5 volts DC.

Here is an example of a Force motor that uses just a Rectifier, not a Regulator/Rectifier so it's not uncommon to see as much as 16 volts DC in this particular set up. It does show you that once the engine reaches the proper RPMs, the DC voltage should slowly climb to maximum voltage and remain there. In your particular application with the Regulator/Rectifier, the voltage should max out at about 14.5 volts DC.

1990 US Marine Power Force 90 - RadioShack Rectifier (3 of 3) - YouTube

 

[jpwilly]

Re: Tachometer not working!

No actually the red wire was disconnected. I just retested with it attached and the readings were stable at 12.5+ at idle and picked up with rpm's although I couldn't get them to stabilize at higher rpms I didn't see anything blink over 14volts DC this time. So that seems to indicate that it's working? So now it seems I may have a faulty tach? Is there any way to remove and bench test it??

 

[gm280]

Re: Tachometer not working!

Is your meter an auto-ranging type? If not, the next time you are reading any voltage, be it AC or DC, and the readings are all over the place, try switching to a higher scale to see if you were trying to read voltages that were over the selected meter range. Another thing, does your meter have a frequency option? Some do some don't. If yours does, switch to that option and connect it to the same place the tach connects. It will read the pulses and display the frequency letting you know you do have a pulsing output to the tach. And then the sad news is your tach isn't taching anymore...:blue:

 

[jpwilly]

Re: Tachometer not working!

Is your meter an auto-ranging type?

I don't know it's the $3 Harbor Freight type made by Cen-Tech http://manuals.harborfreight.com/manuals/98000-98999/98025.pdf

 

[pnwboat]

Re: Tachometer not working!

Normal battery voltage on a fully charged battery is 12.7 volts DC. 12.5 volts at idle is just reading the battery voltage. The fact that you can't seem to get a stable reading, and not over 14VDC is a concern. The voltage readings you see should act similar to the readings that are in the video link I posted. Only difference is that yours should max out at 14.5 VDC. Might try as GM280 says and set the meter on the 200V range and see if the unstable readings are easier to read. I'm assuming you are using the 20V setting on your meter right now.

One other thing, try reversing the two yellow leads connected to the Regulator/Rectifier to see if that has any affect on the tach. It will not hurt anything because this is AC voltage and there is no polarity as with DC voltage.

You could try temporarily installing a simple full wave bridge rectifier as a test, but it'll cost you $5 from Radio Shack. Part# 276-1185
25A, 50V Full-Wave Bridge Rectifiers : Rectifiers | RadioShack.com

Pretty simple to hook up. It has 4 spade lug connectors. Two yellow wires go the lugs for AC input marked with the ~ symbols, ground wire goes to the ground lug marked with the - symbol, and the red wire from the battery goes to the lug marked with the + symbol. Tach wire goes to one or the other lugs connected with the yellow wires. If the tach doesn't work on the first yellow wire, try it on the other.

If the DC voltage increases to about 16 volts DC, then I would say your original Regulator/Rectifier is not working properly. If the tach starts to work, then all you need to replace is the Regulator/Rectifier. If the tach still doesn't work, you might have to replace both the Regulator/Rectifier and tach.

 

[jpwilly]

Re: Tachometer not working!

Swapped in a new universal reg/rectifier and still nada. Guessing that the Tach is the issue. I think when I get some time I'll pull it out and test it at the motor I have no gear to trouble shoot the tach on a bench.

Anyone know of a place that will repair or sells inexpensive 12 pole tachs even a used unit verified to work would be great too.

Anyone know of a FREE pdf service manual for the 1993-1994 force 120?

 

[pnwboat]

Re: Tachometer not working!

Might check these folks out for a 12 pole tach. Not that cheap though.

Outboard Only Tachometers , Tachometers , Individual Gauges , Boat Gauges | Great Lakes Skipper

Check some of the auction sites for cheaper ones that are used.

 

[jpwilly]

Re: Tachometer not working!

Looks like a good company. This one looks nice for just $60 Faria TC50184 White 7000 RPM Outboard Boat Tachometer Gauge | Great Lakes Skipper