tachometer or regulator

[Daniel1947]

89 V6 150HP....tach is not working... all wires hooked up and ground and +voltage to back of tach. Gray wire from sender connection on tach back to bullet connector at regulator shows continuity. Is there any way of determining whether problem is with tach or regulator. Other gauges and charging system all operating normally. I know I can get a tach for $50 - $70, but if it isn't the tach it is money wasted since most places won't accept returns on used electrical parts. I am sure there must be some type of "pulse signal" from the regulator, just not sure I can read it with a VOM.

Thanks to everyone in advance as is usual,

 

[delta229]

Re: tachometer or regulator

I'm not sure that this will help you much but normally the grey wire is for lighting and the tach wire is yellow on most systems. The tach signal is too fast for a basic DVM. I use an oscilloscope to look at tach signals.

 

[mercurymang]

Re: tachometer or regulator

You might try moving the grey wire for you tach over to the other leg on the regulator. If one leg is bad, the other may still be good and it will stop working. Nine times out of ten the regulator is the issue.

 

[Daniel1947]

Re: tachometer or regulator

I appreciate the info, but the 3 wires on the back of the tach are black (ground) purple (+12 volts/battery) and gray. There isn't another leg on the regulator that I am aware of. Regulator has 2 reds, 2 yellows, a purple and the gray.

 

[belairbrian]

Re: tachometer or regulator

I'm not sure that this will help you much but normally the grey wire is for lighting and the tach wire is yellow on most systems. The tach signal is too fast for a basic DVM. I use an oscilloscope to look at tach signals.

Nope, Grey is tach signal. Lighting is at the discretion of the boat builder. But not uncommon to see the purple used for instrument lighting as well as gauge power.

Wiring Color Codes for Mercury & Mariner Outboard Motors.

 

[mercurymang]

Re: tachometer or regulator

I appreciate the info, but the 3 wires on the back of the tach are black (ground) purple (+12 volts/battery) and gray. There isn't another leg on the regulator that I am aware of. Regulator has 2 reds, 2 yellows, a purple and the gray.

Actually the two yellow wires were the legs I was referring to. On a traditional setup, you would just have a rectifier which took the voltage from the two stator(yellow) wires and turned it to dc. The tach was simply driven of one of the two yellow legs. You have an incorperated rectifier/regulator which has a specific tach out wire (I'm not sure but it probably is just driven off one of the two stator inputs). I suspect your unit is defective. Do you get a higher voltage at WOT than you do at idle? If so, your rect/reg unit probably needs to be replaced.

 

[Daniel1947]

Re: tachometer or regulator

LOL, that really isn't what I wanted to hear. I have not checked voltage at WOT, but guess I will do that and hope it is OK. Expense wise, I am hoping it is the tach.

Thanks

 

[MH Hawker]

Re: tachometer or regulator

First off is it charging the battery. If it isnt then you have found the problem.

 

[Daniel1947]

Re: tachometer or regulator

OK, I will have the boat in the water this weekend. I have a Milton battery/charging system checker that will show the charging system output. If the charging system is operating within specs, that is not overcharging at WOT, or undercharging, is it safe to assume it is the tach? Or can it still be the gray wire withing the regulator?

 

[oldman570]

Re: tachometer or regulator

The gray wire in the rectifier/regulator could be bad. First switch the yellow wires and see if that makes the tach work. If the tach still dose not work. if it still doesn't use a pointed test lead for the meter and place it in one of the yellow connections and have the tach gray lead hooked to the other end. Test each yellow connection and see if the tach works then. The tach works off the current flow of the stator. If the tack still will not work, then the tach or stator is at fault. The CDI and Faira websites gives complete test procedures for testing the stator and rectifier/regulator units and the tech service is very helpful.
Oldman570