ground wire getting warm

[dennisrhall]

last fall i rewired my lights, because of old wireing, now i have rewired some wires on the eng. because of old wire, i had cut the ground wire on the battery last fall and just found it, now after rewireing (the ground wire) insulation will get warm when i crank the eng.(the small wire from the battery to eng. block.) all the wiring should be correct. help help, thanks.<br />1967 65 hp merc.

 

[DHPMARINE]

Re: ground wire getting warm

Dennis, just a few ideas.<br />Dirty connection either end<br />Cable internally damaged (corrosion)<br />Lengthy cranking of starter.<br />DHP

 

[remmer38]

Re: ground wire getting warm

Small wire to the block? Battery + to rectifier red heavy guagewire. Battery - to starter ground (bolt holding starter in place) black heavy guage. They should be like car battey cables as the amps are so high. Also corrosion kills. Take it from a ex navy corrosion expert (airdale). Make sure there arent any cooroded connections. Take a wire of one by one and wire brush em up. There are non problematic corrosion sparays and applications to ensure a good electrical connection. Its nice to get intimate with your motor if you have time. Get under the hood and learn. Attention to small details might in the future help to see something out of place , loose, etc..I am sorry to be long winded. Catch a fish.

 

[dogsdad]

Re: ground wire getting warm

I think the corroded wire theory is probably right on the money.<br /><br />Heat is a result of power disipation, and that is always due to some amount of resistance. Though an ohmmeter may say a wire has no resistance, or 0 Ohms, there is actually always some miniscule amount of resistance in a wire. If it was actually 0 Ohms, it could carry infinite current (or Amps) and that is absurd and impossible. So, 0 Ohms is actually an impossibility---it would be dividing by 0.<br /><br />Uuhhh...I think you have a corroded wire, or one that is too small.<br /><br />-dd-

 

[dennisrhall]

Re: ground wire getting warm

thanks for the info, i'll check it out today and reply back with what i find

 

[dennisrhall]

Re: ground wire getting warm

corroded !!!!!!!! very much, both hot and ground. (main cables from eng. to battery) now what? new harness? can this one be fixed? <br />has anyone have one for sale for a 1967 mercury 65 hp ser # 2164811?????

 

[rickdb1boat]

Re: ground wire getting warm

If it's just the wires from the battery to the engine, run up to your local auto parts store and get ya new ones. No big deal... Also, if they only have them in black, paint one red so you don't confuse them.<br /><br />Also, here is a site for some parts if you need them:<br /><br /> oldmercs.com

 

[dennisrhall]

Re: ground wire getting warm

I want to thank all who had input on my ground wire problem, i replaced some cables and it fixed the problem, once again thanks.

 

[Dwain B]

Re: ground wire getting warm

I know you have fixed your problem and congratulations. Just for future reference...the easiest way to check for power loss through a cable is a voltage drop test. It is MUCH more accurate than an OHMs test. Connect one lead of a digital voltmeter to the positive side of the battery and the other lead to the positive lug on the starter. While cranking it should NOT have over .2 volts. On the negative side...same way. One lead on the negative terminal of the battery and the other lead on a good ground of the starter. If any reading is over .2 volts then clean connections. If reading is still over replace cables. Also can use the same technique on the charging system although the engine needs to be running for the test. Hope this helps with future wiring diagnosis.

 

[dogsdad]

Re: ground wire getting warm

I agree with Dwain 110%! I should have thought of that myself. When you're talking 10, 20, or 30 Amps, even a tenth of an Ohm can become significant. At 30 Amps of current draw, and 1/10 of an Ohm of extra resistance, you'll lose three volts! It's much easier to measure a voltage drop across a wire under load than it is to try and measure tenth of an Ohm on a cable.<br /><br />Hats off to Dwain!<br /><br />-dd-

 

[remmer38]

Re: ground wire getting warm

Thats called a megermeter. Ever heard of a TDR