Gremlin in electrical system. Need Help!!

willdarbyy · Apr 28, 2011

89 Merc 470 w/ Alpha 1

Turn key guages come on everything is happy. Try to crank get one click then nothing and guages die. Turn key off and on nothing. Try 20 minutes later guages come on one click guages die. I have checked voltage to starter, starter solenoid, slave solenoid (replaced), both sides of 50 amp circuit breaker, key switch (replaced because key was broke off in it) and checked it again, cleaned plug in wiring harness, and checked grounds. I am officially lost. Thanks for your help.

Don S · Apr 28, 2011

Re: Gremlin in electrical system. Need Help!!

Checking voltage doesn't really put a load on anything, and you are loosing things when you put a load on them.
Time to start looking for loose battery cables, corroded terminals on the ends of your cables, bad connetions on the main harness connection at the engine, (to name a few). Check everything including getting the batteries load tested. Again, you need the load to test things to find the problem. Lots of things could cause your problem.

Bondo · Apr 28, 2011

Re: Gremlin in electrical system. Need Help!!

Time to start looking for loose battery cables, corroded terminals on the ends of your cables, bad connetions on the main harness connection at the engine, (to name a few). Check everything including getting the batteries load tested.

Ayuh,... 'n Especially the Grounds...

willdarbyy · May 10, 2011

Re: Gremlin in electrical system. Need Help!!

Ok so, all the things mentioned above had already or now have been completed. Still no luck. While scratching my head in ponderence of my problem and continuing to test things I noticed something strange I had voltage to the block. Automatically assume one of the positive wires is frayed and causing this problem. Checked all the wires that come anywhere near the block and they are good. As a test I unplugged the main harness and all of a sudden no voltage on the block. Harness plugged in voltage where it shouldnt be, un plugged everything is happy. I started chasing wires but was cut short by rain. So for all the experts out there any suggestions on where to start or any likely suspects. Thanks in advance.

Lyle29464 · May 10, 2011

Re: Gremlin in electrical system. Need Help!!

where are you putting the test leads?

If you have the plus on the block where is your black lead?

Battery in backwards? battery charged backwards?

If you have a digital and your leads are in the meter wrong your meter might say -12 volts?

do you drink? ok ok kidding. please run a test again and start at the battery.

willdarbyy · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

Well when I noticed voltage on the block one the black test lead was attached to the ground bolt on the back of the engine, the other was touching the starter bolt. So I had 12 volts from the starter bolt to ground. To make sure I took a jumper wire from the ground bolt and touched the starter bolt, pretty sparks. Yes I have a digital meter and I understand that if the black lead is on the positive side and the red lead is on the negative side it will just show negative voltage but it still reads whats there. Voltmeter was set up correctly and working just fine. Batteries are all correct. Again problem disappears when the harness is unplugged.

Yes I do drink Crown Black or an ice cold bud light if you please.

Lyle29464 · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

By starter bolt I think your talking about the bolt that has the hot wire from the battery attached to it? That would be normal. When you turn the key that should still be 12 volts.
If it goes to zero It is just telling you the same thing the guys above are. Bad connections will not carry any current. Maybe just enough to make the click and read 12 volts but not turn the engine over. A cheap load tester will let you check the start system in a hurry. Or just do what the other guys pointed out. Check connections, terminals and grounds.

willdarbyy · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

No, sorry if I was unclear. I am talking about the starter bolt that bolts the starter to the motor. Not the bolt on the solenoid where the positive battery cable runs to.

fossill · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

Either your battery is junk (did you try boosting it?), the cables and battery terminals need a thorough cleaning with a proper tool, or you got a bad ground connection from the battery negative or a poor positive connection to the starter.
99% of the time it's one of the above with the problem with the symptoms you described.

wifisher · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

If you are reading voltage between the starter bolt and a ground cable, you have high resistance between the two. A starter bolt should be a good ground.
Remove and clean the ground bolt you were using and the starter bolts,starter and block where they are in contact.

willdarbyy · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

Battery is brand new and has been tested twice at the parts house now and countless time by me. The cables are in great shape and are reading like they should i.e. voltage drop resistance etc. Starter bolts are brand new and the surface is clean as new money. The block ground post is spotless and tight. And its not just the starter bolts tht have current anywhere I touch on the block to the ground has current. When the wiring harness isnt plugged in everything is as it should be as soon as I plug in the main wiring harness I get voltage across the block. Thanks for all the suggestions so far guys.

81 Checkmate · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

Is the key still on when you are unpluging and pluging the harness up? If the key is on and you plug the harness up you would think that you should have voltage the the other half of the plug. Right! If key is off you should not be getting voltage to the motor.
So it would have to be something after the plug that is giving you voltage.
Just a thought.

By the way what are we working on?

NHGuy · May 11, 2011

Re: Gremlin in electrical system. Need Help!!

Sure sounds like the problem I had last spring.
After countless tests, cleanings & dielectric treatments I finally solved it by gently sanding the plug contacts on my main plug with emery cloth. I wrapped up fine emery in the shape of a tube and just roughed up the "male" prongs. I was afraid to really go to town on them for fear of removing any tinning treatment they may have had. I also used a knife edge to split the prongs a bit where they join together. This made them contact the insides of the sockets better. Just don't open them too far or they won't go into the sockets.
Give that a try, it worked on my 89.

Gremlin in electrical system. Need Help!!

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