Installed new Tach but Doesn't Work

[scout-j-m]

So I finally bought a new Faria tach to replace the old one that hasn't worked the entire time I have owned the boat. Getting a new tach was a pretty big deal as my 1994 70HP Force has never run right and I am committing myself to fixing it this spring/summer.

Anyways, I set the tach to the 12 pole setting and installed it no problem. My fuel system was disconnected so the motor wasn't going to start but turning the motor over the dial didn't budge. I checked the voltage between the power terminal and negative terminal of the tach and got 11.8V so I know it has power and a good ground. The connection of the sender wire to the tach is solid as well. Before getting into all of the rectifier/regulator tests, can I check the voltage directly at the sender wire at the tach and directly where it comes out of the rectifier? If I read previous posts correctly it should see about 18V AC and fluctuate with RPM increase. If that doesn't work can I jump the gray sending wire coming from the wiring harness butt connector directly after the rectifier to one of the yellow stator wires' butt connectors and expect to see the tach work?

I'll go through all of the necessary rectifier tests when I have the time but currently working on some other issues to get this thing running right is a higher priority. I would just like to get a tach signal by jumping the rectifier so I can perform other checks, set idle, etc.

 

[Jiggz]

You need to check to make sure the rectifier is working properly before you can check if there is any signal going to the gray signal wire. First check voltage (AC) across the two yellow wires. There should be at least 12VAC at idle across these two wires. Next check make sure there is voltage output on the red wire off the rectifier, there should be DC voltage again approx 12VDC. Finally, you can check if there is any signal voltage on the gray signal wire, this should be AC voltages and it should be approx 12 VAC. If there is no voltage signal off the gray wire, you can try connecting it to one of the yellow wires. Assuming you have AC voltages off the yellow wires, you should have rpm indication on your tach. If not, then the tach could be faulty.

 

[scout-j-m]

Thanks Jiggz. Those will be pretty easy checks.

 

[scout-j-m]

I wanted to bump this thread of mine back up. As you may have seen, I have a current running thread of the rebuild of this motor. I wasn't able to get to any running stator checks before I got into that. So now that the stator is off I plan to do a bench test of it. I know how to test the resistance of the high and low speed wires that go to the cd pack, but I couldn't find anything on bench testing the the resistance of the two yellow wires which connect to the regulator/rectifier. Can that be done and if so what values should I look for?

Also, is there a way to bench test the regulator/rectifier?

I would like fix this issue at the same time as I reassemble the motor from the rebuild so I can get straight into the break-in and have a working, trustworthy tach to go by.

 

[pnwboat]

The resistance across the two yellow battery charging windings is very low. Around .6 OHMs. Less than 1 OHM, almost a dead short, but not quite.

I've never seen any resistance readings for the regulator/rectifier. It's not a simple circuit with just a couple of diodes, so you probably can only test it under actual operating conditions, or some type of test rig that simulates actual running conditions.

 

[scout-j-m]

Since they are so cheap, I think I am going to go ahead and buy a Radio Shack rectifier. I figured that way whenever I get my rebuild done I will have it just in case. Is the one in the link the recommended one to buy? If so does it install basically the same as the OEM one I just have to join the gray tach wire in with the connection of one of the yellow stator wires to the rectifier?

 

[gm280]

The radio shack rectifier will only work on a two wire output stator setup. If you have three wires or more coming from your stator, you will need a 3-phase type rectifier. And since they offer a rectifier/regulator AND a regulator by itself for your engine, you need to determine which one you have. And make absolutely sure your rectifier/regulator it is bad because those rectifier/regulators are not cheap... JMHO!

 

[Jiggz]

Yes, in your case the Radio Shack rectifier will work. And yes, the gray wire will just connect to either of the two yellow wires. And finally, yes, the connections are basically the same, two yellow wires for the input terminals and two wires (black-connects to ground and red-to battery) for the DC output terminals. The only disadvantage is that you will not have a voltage regulator which the original unit has.

 

[scout-j-m]

Yes, in your case the Radio Shack rectifier will work. And yes, the gray wire will just connect to either of the two yellow wires. And finally, yes, the connections are basically the same, two yellow wires for the input terminals and two wires (black-connects to ground and red-to battery) for the DC output terminals. The only disadvantage is that you will not have a voltage regulator which the original unit has.

Thanks. Is they any way to add an aftermarket regulator also?

 

[scout-j-m]

Possibly a regulator like in the link installed downstream of the rectifier?

 

[Jiggz]

I see only one problem with that DC-DC converter and it's amp rating is just 3A. That is very low considering the old one was rated either 9 or 14 Amps depending on the model. With 3A it'll probably burn out almost instantaneously or stay tripped if the overcurrent protection works at all.

 

[scout-j-m]

I didn't even pay any attention to that aspect. I may just end up buying one of the universal rectifier/regulator combos others on this board have used that is around $40. More than I was hoping to pay but much cheaper than OEM or the CDI Electronics one.

 

[scout-j-m]

Wanted to add, I bench tested (diode test) my current rectifier/regulator tonight according to this video. Looks like it is definitely bad. So I will for sure go ahead and order a new universal one.

 

[scout-j-m]

BTW Jiggz, the universal one I am thinking about getting is part #01-154-16. I saw your review on Amazon for it. It only has 2 stars on there though overall. How is yours holding up? I was wondering if the bad ratings were from truly bad units or just uninformed buyers who installed wrong. Either way, at least I know how to do a diode bench test before I waste time installing from the video above.

 

[Jiggz]

Mine is holding up perfectly. But I cannot blame the reviewers for the bad reviews because there is a lot of inconsistencies on the quality of the unit. I guess I got lucky either that or I installed it correctly the first time. When it comes to electronics, there is no such thing as second chance. Either you did it right the first time or you will need a new one. As for testing diodes which is basically what rectifiers are made of, it is all about high and low resistance on forward and reverse bias reading. Minimum ratio of resistance (fwd and rev) should be no less than 10, the higher the better.

 

[scout-j-m]

Well now I know how to install it right at least. I will order it and install it but leave all of the connections taped off on my first start. Then do a quick test on the stator leads and if they check out with acceptable AC voltage shut it down, hook it up correctly, and cross my fingers lol.

 

[Jiggz]

Actually you don't even have to do such testing to start with. Just make sure all connections are correct and most importantly the body of the rect/regulator needs to be grounded. It is this grounding that provides the shunting of voltages for the regulator to work. I used dielectric grease with all connections to protect them from dirt including the body grounding. One thing about this rect/regulator unit is when you attached the gray wire to one of the yellow wires sometimes it doesn't send signal to the tach. The fix is to switch to the other yellow wire and for some reasons it works.

 

[gm280]

There are literally tons of bridge rectifiers available from so many electronic part places to replace yours. And some have higher ratings as well. But unless you really screw up the install, the radio shack will work. But there will ne no regulator either. A regulator to handle that much current will cost as much as the OEM unit. You may do a web search to see if you could get the combo rectifier/regulator on the cheap... Just an idea...

 

[scout-j-m]

There are literally tons of bridge rectifiers available from so many electronic part places to replace yours. And some have higher ratings as well. But unless you really screw up the install, the radio shack will work. But there will ne no regulator either. A regulator to handle that much current will cost as much as the OEM unit. You may do a web search to see if you could get the combo rectifier/regulator on the cheap... Just an idea...

The universal combo one on amazon is only $36. I'm going to give it a try.

 

[scout-j-m]

So I ended up buying this one off of Ebay a couple of weeks ago. I just now got around to bench testing it prior to installation. The reverse bias test was good between each yellow wire and the red positive one. I got resistance in only one direction for each. However, when I did it between each yellow wire and the ground I got no reading either direction. According to my factory service manual and all of the videos I have watched this means the unit needs to be replaced/sent back. Is this true? Should I go ahead and install it and see? I can still return it and the seller doesn't explicitly say installed electronic components can't be returned like many do.