gauges on a 743b

[dale2]

Hello first time here and have some questions. I am rewiring a 743b bobcat and m wondering if the gauges operate on the full 12 volts or is there some kind of reducer for them. Also if some one has a schematic that shows the pinout of the light switch would be a great help
Thanks
Dale

 

[foton]

If I remember right everything on those is 12 volt dc.

 

[dale2]

If I rememb

If I remember right everything on those is 12 volt dc.

Could there be a piece of resistive wire in the harness to lower the voltage to the gauges? The reason I ask is I have ruined a new fuel gauge and my temp gauge pegs out hot as soon as turn on the key. I feel like I am applying to much voltage.

thanks
Dale

 

[laurencen]

from all the work we have done on the 743 they are indeed 12 volts

 

[foton]

some gauges will do that if the grounding is bad or to resistive. It would not hurt to put a voltmeter on your electrical system and see what you got. I have used digital volt gauges on small engines and lost the ground and burned the gauges up,old analog gauges did not suffer from that issue.

 

[dale2]

some gauges will do that if the grounding is bad or to resistive. It would not hurt to put a voltmeter on your electrical system and see what you got. I have used digital volt gauges on small engines and lost the ground and burned the gauges up,old analog gauges did not suffer from that issue.

These are analog gauges. I dont understand a missing ground blowing up the gauge. The gauge is a seris circuit completed by the current path to ground thru the sending unit. The ground is only there for the bulb to work. I must be missing something. Please explain more
thanks
Dale

 

[oiu789]

A short in the wire going to the sender will blow the gauge. The gauge needs to see a resisted. Disconnect the wire from the sender and gauge and check it to ground. You can also check it by disconnecting the gauge and checking the ohms from that wire to ground. There should be some resistance depending on fuel level or temp.

 

[dale2]

A short in the wire going to the sender will blow the gauge. The gauge needs to see a resisted. Disconnect the wire from the sender and gauge and check it to ground. You can also check it by disconnecting the gauge and checking the ohms from that wire to ground. There should be some resistance depending on fuel level or temp.

you have a good point there. I know there has to be resistance in the sender wire. but I was holding everything in my hands and I bet I shorted the sender wire on the gauge to ground and I bet that is what blew the gauge. as i did deeper and have been told they do work off 12 volts it is starting to make sense.
Thank you for your time and reply
Dale

 

[dale2]

you have a good point there. I know there has to be resistance in the sender wire. but I was holding everything in my hands and I bet I shorted the sender wire on the gauge to ground and I bet that is what blew the gauge. as i did deeper and have been told they do work off 12 volts it is starting to make sense.
Thank you for your time and reply
Dale

But thinking more. I have checked other gauges by shorting the sender wire to ground and never blew any of those. Is that a bobcat unique thing
Dale

 

[oiu789]

But thinking more. I have checked other gauges by shorting the sender wire to ground and never blew any of those. Is that a bobcat unique thing
Dale

Could have been what type of gauge you did that to. Say one that uses very low ohms to work with.

 

[oiu789]

What does your senders ohm out?

 

[dale2]

What does your senders ohm out?

i dont know what it ohms out at. I cant get the cage up right now so I cant take it out. Do you know what it should be at full and at empty. I am going to get the gauges and that one will be the last one I install. By then I will be able to get the sender out and check it.
thanks
Dale

 

[oiu789]

Are you asking about the fuel sender? No I don't. Some one out there might. Watch this you tube video you. "" search you tube for more on how to test. your sender. The ohms may not be exact as in the video but some where close. The temp sender is on the eng and should be accessible in the eng compartment. Just unhook it and check between terminal and ground. Any fuel sender will give you some in the ball park readings. Here is what I found on a google search. For the standard American version sender (240-30 ohms), you will have between 232 to 252 ohms @ empty, and 28 to 36 ohms @ full.