Problem with Motorguide 36 volt

[MDRookie]

Hi all... hopefully I can describe this well enough for you to understand....

I came into this transom motor a few weeks ago and finally got around to wiring it up.. along with a bow mount on a single 36v bank using a switch. Transom motor didn't come on first hook up... but the bow mount did. So I disconnected bow motor from switch and connected the transom wire to that side of the switch and the motor ran. Shut it down and reconnected the bow mount to the other side of the switch... and it ran... but then transom mount wouldn't come on again. So.. I disconnected all battery connections and motor connections...reattached.. it came on. I let it run for a few minutes to see if wires get warm... they didn't. Switched over to the bow mount to see if those wires get warm... they didn't. Shut it off for a bit and came back to it 10-15 mins later. Transom motor wouldn't come on again. Rewired again... still nothing. So.. I cut all my connectors off that I put on to extend the length of wire to see if that was the problem... I then decided to connected the bare wires of transom motor directly to battery posts 36v... still nothing. I tried connecting it to just 12 volts and nothing. I was getting frustrated now! Walked away for a bit. Neighbor came over to assist and we checked under the head of the unit.. visually inspecting and checked the switch for continuity and what not... all was good. Then for whatever reason I decided to try it on 24 volts... It came on! I was like what the heck? Then I immediately moved the positive lead over to 36 volts.. it continued to work. I was like.. what the heck again. I removed the leads for a few minutes.. would not start up again on 36 volts.... but it will when I moved a lead to 24 volts and will continue to run when I move the lead over to 36 volts. I'm not sure what's going on... Can anyone explain to me why this is happening? It seems when I get it running with a jump start from 24 volts and let run for a minute or so on 36v.. it stays energized enough that I can remove a lead for up to 30 seconds or so and place the lead back on the terminal... it will continue to restart. If I let it sit for a few minutes... it seems to me that it discharges and won't start unless I hit 24 volts first. I hope this makes sense... Thanks in advance for any help

[TheRodFather]

Tough to understand exactly what you are describing.  Can you post a schematic of what you are trying to accomplish?

 

The startup issue you are having is likely due to a startup capacitor that is discharging over time, and doesn't have enough oomph to get the motor turning after a period of non running time. 

 

The higher the voltage an electric motor is designed to run at, the less current (amps) is used to produce the same power (smaller wire can be used, more efficient, etc).  BUT, high amps are needed to get a motor to start moving, thus a capacitor is used to give off a burst of energy for initial startup.  24v is less voltage, but more amps are drawn, thus your TM is able to start, and when you switch to the third batt, the startup amps are not needed, just running amps, which can be quite different from each other.

 

HVAC blower motors work the same way, when the capacitor fails, you can get the blower to spin by bump starting it, and then the electricity takes over and spins it at the proper speed, but it wont restart from stopped.

 

I'm not sure I understand what you are trying to accomplish.  Are you running 3 batteries in series, one trolling motor uses all three batts, and a second trolling motor is a 24v, or they are both 36v, and you would like to switch in between the two?  What size wire and length are you using, etc.  Is this TM used?

 

 

[MDRookie]

Hey Rod.. Yes I want to run two 36 volt motors off a single bank using a battery switch between the two. This transom motor is older... 90's. I got it from a friend who got it from a friend and it was working fine for him. I brought it to an "authorized service center" and he gave me a call the next day saying it was working fine for him. He said he'd leave it on the bench and show me when I got there. I was shakin my head the whole way there.. as I know I did everything correct with excellent batteries. So.... I get there and he turns it on and NUTHIN! I was like... there you go.. It didn't make a liar out of me! He flicked in on/off multiple times.. checked connections.. all the stuff I did and still nothing. I asked him to connect to 24 volts.... it started! 

 

He scratched his head and said don't know what to tell you. I said I hoping you can tell me you can fix it! He said it's too old and they don't have parts for it. I threw it over my shoulder and left disappointed. 

 

My friend and I thought capacitor as well. I don't think I'll be able to find anyone to work on it....  Thanks for your response!!

[TheRodFather]

No problem, I guess it depends how bad you want it to work.  New components can be soldered in if you can figure out what exactly is wrong.  

[WRB]

90's era 36V transum mounted TM, who made it? I understand a 36V bow mount TM.

The 1st thing to check is the voltage at each TM connection. Splicing wire to extend it is a bad idea with DC as it adds resistance. The wire should be 6 gage marine multi strand copper wire. Do you have a 36V 50 amp battery switch?

It's hard to understand what you are doing without a wire diagram.

Tom