Adding voltage gauge - questions

[timsch]

I'm trying to hook up a voltage gauge to my L275. The main problem I'm having is that my wiring is in such bad shape that I don't have a lot of working options that I see. None of my lights are connected. The only fuse of the 4 on the panel that has wires running to it is the far left one.

I was hoping to tap into a positive wire that is only on when the key is on. Maybe I'm just thinking of a gas engine that needs power to the ignition before starting, which wouldn't apply here with a diesel. It seems that one of the wires coming off of the dynamo might be a good option, but I'm not sure which one, not having probed around it while it is running yet.

I could just hook it up to the starter positive, but that is always energized. Not knowing whether there is any drain when a gauge is hooked up and always reading battery voltage, I was hesitant to do that since this tractor can set long times without being run and didn't want to kill batteries (I will eventually run power to my shed to keep the tractor on a trickle charger, but that hasn't happened yet).

Can you tell me

1) what good wiring options I have, and
2) let me know if the voltage gauge would not drain the battery at all if always connected?

 

[RBsingl]

Probe the 2RW lead from your key switch that feeds the pair of 10 and 20 amp fuses to see if that is "hot" only in the on position. I believe that is the case but confirm with a meter to be sure because schematic represenations of switches have never been standardized.

A typical low cost analog DC panel meter movement will have a sensitivity of 1,000 ohms per volt so a 15 volt movement will draw about 1 mil when connected to a nominal 12 volt battery and it would be fine to leave it connected without concern. But LCD displays draw a bit more and LED displays draw significantly more so I wouldn't leave one of those connected all of the time to a tractor that doesn't get regular usage.

Rodger

 

[North Idaho Wolfman]

You want to hook to the AC terminal or wire off of the switch.
Do not hook to the dynamo wiring.

 

[85Hokie]

As North Idaho Wolfman said - do not hook to dyno - that is producing AC only !!!

Are you using an Analog gauge or digital? I have found the cheap digitals do NOT last very long. Then again money talks and the rest walks

 

[timsch]

It's one of these units. No idea of country of origin, but they seemed well regarded enough.

 

[timsch]

I probed the 2RW at the connector and then at the switch connection with the key in the ON position and got 0 Vdc. I probed the 2BW connection at the switch and got the same. I'm not sure what to make of that. The tractor turns over and runs fine.

 

[InTheWoods]

^That's weird. You sure you are making good contact with your probe? Got the other probe on a good ground?

It could be your keyswitch is dead or mis-wired somehow, and that's why, In which case, you might be screwed until you get that sorted.



Assuming your keyswitch works, can you find these fuses? Personally, I'd hook to the point shown with my green arrow, as the wiring I'd put there would then be fuse-protected at 10 amps.

Hooking directly to the key switch side (AC, 2RW) is all before the fuse, and thus poses a bit of a fire risk if you have a short. Bad practice.

 

[timsch]

Well, I'm deep into the bad practice then. The 10A @ 20A fuse are easy enough to get to, and would have been my preference, but were bypassed by a PO years ago. I've had the tractor for about 7 years now. I knew the wiring was bad when I got it and made some improvements, but not nearly all, and not those most important ones since we're talking fire hazard....

I just got finished up wiring the gauge to the + on the starter and a ground on top of the engine. I put an automotive disconnect on the + wire for longer times of inactivity. Works fine, but yes, I should put rewiring those fuses back in circuit high up on the list.

 

[Russell King]

I have a L185 and was able to get the fuse block from the dealer. I looked at yours and it is a different part number and is discontinued. You may want to see if the ~$100 part from the L185 would work or you can probably find a way you repair yours if it is really messed up, it might just need to be cleaned up. I am pretty sure there is enough room under the dash to fit a newer style fuse holder(s) and use existing cover to get access.

 

[GreensvilleJay]

hmm,
if it's on the BIG +ve ( battery) of the starter, it'll drain the battery..might take 2-3 days ...
if it's on the ST lug, it'll only show maybe 8-10 volts while actually spinning the starter.

 

[Old Machinist]

You should never have anything connected un switched. Since you connected it to the starter positive I suggest you remember to turn the switch you installed off before disconnecting the battery. I am surprised there hasn't been more of a problem from modern vehicles having a memory draw. They always spark when you reconnect the battery.

Years ago I had a battery explode in my face. I was charging it with an old charger that had a built in amp AND voltage meter. When I disconnected the leads the draw from the voltmeter caused a spark. There is a reason you don't see voltmeters on battery chargers.

 

[TheOldHokie]

Well, I'm deep into the bad practice then. The 10A @ 20A fuse are easy enough to get to, and would have been my preference, but were bypassed by a PO years ago. I've had the tractor for about 7 years now. I knew the wiring was bad when I got it and made some improvements, but not nearly all, and not those most important ones since we're talking fire hazard....

I just got finished up wiring the gauge to the + on the starter and a ground on top of the engine. I put an automotive disconnect on the + wire for longer times of inactivity. Works fine, but yes, I should put rewiring those fuses back in circuit high up on the list.

Inline fuse holders are nearly universal and dirt cheap.

Dan

 

[imarobot]

I've wired in meters to only be on when the key is on and also added a momentary switch to power always on. This way I can check battery voltage if needed without a key.
Both lines should be fused.