struggles to start & battery posts getting hot
Thread Starter
Junior Member
Joined: Oct 2017
Posts: 35
Likes: 3
2007 r320
struggles to start & battery posts getting hot
This is the wife's vehicle, and the other day pulling into work, she had some smoke billowing out of the hood and from the passenger side of the car. So she left the car there and I came to have a look. I couldnt see any major wire damage or notice anything melted etc. I then tried to start the car and it just slowly tried turning over but nothing. I figured the battery might have been low, so I brought the battery home and put it on charge. This battery is only a month old but figured you never know. The next day I returned with the battery after having it on charge, hook it up and try to start the car and the exact same thing. Struggles trying to turn over, and the battery posts get hot, also the positive boost terminal under the hood gets very hot to the touch.
Could this be a starter issue, or just simply a loose connection or wire somewhere.
Not long before this, I had the taillights burn out and a passenger side low beam. Might be unrelated, but in these cars I never know.
Anyone have any similar experience?
Could this be a starter issue, or just simply a loose connection or wire somewhere.
Not long before this, I had the taillights burn out and a passenger side low beam. Might be unrelated, but in these cars I never know.
Anyone have any similar experience?
Junior Member
Joined: Aug 2016
Posts: 72
Likes: 10
From: Ottawa, Ontario
2015 Cadilac Escalade ESV, 2010 MB R350 Diesel
First, if the starter draws a normal amount of amps, then the place the wiring is hot, is the place where there is a problem. Check to make sure there is no corrosion on the terminal connectors. Use a volt meter to check the voltage at the connector side of the battery and try starting the car. Then do the same while testing the voltage on the battery posts. If there is a difference, then there is where the problem lies. You can check connections from there on out. The boost terminal on my car gets hot as well, but the car starts fine. You can buy a cheap amp clamp at any parts store to help in the diagnostics. The starter should draw about 180 to 220 amps when cranking. Good luck.
Super Member
Joined: Jul 2009
Posts: 938
Likes: 53
From: Montreal, Canada
2005 C240 2011 R350
if it is a frayed wire rubbing and shorting out on chassis ground you would see smoke and sparks from where it is coming from
I have had a shorted alternator on a car that had exactly the same symptoms..
You could boost it with another car, it would start but as soon as you disconnected it stalled. Booster wires getting very hot.
easy to diagnose anyway.. OP should just check his wiring and even remove the alternator + cable to see if it fixes the problem.
I have had a shorted alternator on a car that had exactly the same symptoms..
You could boost it with another car, it would start but as soon as you disconnected it stalled. Booster wires getting very hot.
easy to diagnose anyway.. OP should just check his wiring and even remove the alternator + cable to see if it fixes the problem.
Thread Starter
Junior Member
Joined: Oct 2017
Posts: 35
Likes: 3
2007 r320
Brought it to a shop, they tested amperage while cranking and it was 400. They say it's the alternator.
I personally looked at all the wiring under the car I could find, and I had all the carpeting and flooring out and followed the main positive cable from battery, to under the hood, then down to the alternator and starter. All connections tight and no frayed wiring. Hopefully it is true starter. The vehicle has 473,000km on it (like 290,000+ miles, and probably originally starter)
so here is hoping. Thank you for the replies, I'll keep the thread active with results
I personally looked at all the wiring under the car I could find, and I had all the carpeting and flooring out and followed the main positive cable from battery, to under the hood, then down to the alternator and starter. All connections tight and no frayed wiring. Hopefully it is true starter. The vehicle has 473,000km on it (like 290,000+ miles, and probably originally starter)
so here is hoping. Thank you for the replies, I'll keep the thread active with results
Super Member
Joined: Jul 2009
Posts: 938
Likes: 53
From: Montreal, Canada
2005 C240 2011 R350
Let me know if I was right! 
If you look at battery alternator starter circuit, there are not many ways you can get such power drain without lots of sparks.
If the starter is shorted it would not turn and your power drain would only occur when you crank.
The solenoid drive circuit is low amperage.
The alternator is the only place where catastrophic failure of the diodes, or perhaps the stator winding can short to ground.
If you look at battery alternator starter circuit, there are not many ways you can get such power drain without lots of sparks.
If the starter is shorted it would not turn and your power drain would only occur when you crank.
The solenoid drive circuit is low amperage.
The alternator is the only place where catastrophic failure of the diodes, or perhaps the stator winding can short to ground.
Last edited by efzauner; Aug 22, 2018 at 07:03 PM.
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Thread Starter
Junior Member
Joined: Oct 2017
Posts: 35
Likes: 3
2007 r320
Let me know if I was right!
If you look at battery alternator starter circuit, there are not many ways you can get such power drain without lots of sparks.
If the starter is shorted it would not turn and your power drain would only occur when you crank.
The solenoid drive circuit is low amperage.
The alternator is the only place where catastrophic failure of the diodes, or perhaps the stator winding can short to ground.
If you look at battery alternator starter circuit, there are not many ways you can get such power drain without lots of sparks.
If the starter is shorted it would not turn and your power drain would only occur when you crank.
The solenoid drive circuit is low amperage.
The alternator is the only place where catastrophic failure of the diodes, or perhaps the stator winding can short to ground.
I am having the starter changed at the same time while in there, but it starts fine with the alternator removed, so definitely alternator was toast.
Thank you for your input and replies, it has been much appreciated!!
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