good afternoon, this past weekend i finished wiring up a new engine panel from catalina direct. when i fired
up the m25 everything worked except the tach. at first it did nothing and then after about one minuet it kicked in and seemed to be registering the rpm's correctly. i shut down the motor and started it again several times with the same result each time. does anyone have any ideas what might cause such a delay. FYI all was well with old tach before the switch and wires are connected the same and tight.
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James DeBrum
S/V Slip Mistress
1984 C36 #333
Charleston S.C.
jgdebrum@gmail.com
Is the tach connected directly to the alternator or to an external regulator?
Nick Caballero
Retired C36/375IA Mk II Technical Editor
Jim-
On our M25 in our 1986 C 30, the tach always had a delayed reading when starting the engine. It worked that way for 20+ years of our ownership and two tachometers. I don't know the electrical reason behind it- maybe it took a while for the amps or volts to build up on the alternator. Strange that your tach is working differently after being moved.
We did have an issue of intermittent tach problems that I eventually traced to the M25 molded wire harness connector. Some wires corroded inside the connector. The connector and pins all looked great visually, and I only discovered the problem when I accidently moved the connector doing some other work. I noticed that when I held the connector/wireharness a certain way, the tach reading went to zero. If you still have the original wire harness connector- I would check it by moving it around and noting if it affects the tach.
Good luck
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
paul, with the new instrument panel i replaced the wiring harness. i also checked my connections to the tach and the panel. all "seams" fine? as a side note i have a friend who replaced his panel recently because of a lighting strike. he said his does the same thing since the new panel was installed.
James DeBrum
S/V Slip Mistress
1984 C36 #333
Charleston S.C.
jgdebrum@gmail.com
nick, it does have an external regulator. there are balmar and acr modules connected to the alternator but i don't know what they do or how they work. they where installed by the p/o and worked with the old tach just fine. i did not have to wire anything different to them or the alternator.
James DeBrum
S/V Slip Mistress
1984 C36 #333
Charleston S.C.
jgdebrum@gmail.com
Hey Jim,
Since you have an external regulator, the tachometer sense wire is likely wired to this instead of to the alternator stator terminal. If this is true, then your tachometer behavior is normal as this is simply reflecting the "soft start" characteristics of many regulators. Usually meant to give the engine a bit of time to warm up before placing a load on the belt. I cannot explain why this is happening with a new panel vs. the old panel other than you simply never noticed it. If your batteries are deeply depleted, you might even notice the engine bog down a bit when the tachometer starts to register. Again, this is just the "soft start" of the regulator.
The ACR is an automatic battery parallel device. Essentially it detects the voltage of two battery banks and automatically parallels them in the presence of an active charge source and separates them in the absence of a charge source. Lots of threads in the forum on that subject.....
Nick Caballero
Retired C36/375IA Mk II Technical Editor
thank you Nick, that makes sense to me. i don't know why it worked with the old tach but understand how the regulator could cause this problem. is there anything i can do to fix it or should i learn to live with it?
James DeBrum
S/V Slip Mistress
1984 C36 #333
Charleston S.C.
jgdebrum@gmail.com
The only way to fix this is to move the sense wire to the stator terminal of your regulator, but then you run into an even worse problem: tachometer cut-out when batteries are nearing fully charged. The lesser of two evils is to live with it.
Nick Caballero
Retired C36/375IA Mk II Technical Editor
thanks for the info Nick. it works perfectly otherwise so i guess ill live with it.
James DeBrum
S/V Slip Mistress
1984 C36 #333
Charleston S.C.
jgdebrum@gmail.com
If I didnt misunderstand;
Check the "minus cable"
Mine had same problem.
Molto,
The delay is not a problem. The external regulator is designed that way. It is supposed to delay its output 30-45-60 seconds after starting. As Nick described above, it is called a "soft start", to enable the engine to get up to speed and get oil circulating before it puts on a load.
Tom Sokoloski
C36/375IA Past Commodore
Noank, CT