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2G Positive battery terminal getting hot after motor mounts

Junzu

Proven Member
127
13
Aug 21, 2021
California
After I did motor mounts! Been chasing this for 2 weeks. I have tried to do some electrical research but am very inexperienced with electricity! Only very basics known, I've been an apprentice tech and haven't touched much electrical issues so this could be a great start to learn.

-Battery removed when doing the mounts. No other tampering with harness except moving it out of the way when necessary (near rear mount)

- Visual check shows no abnormalities or obvious wires grounding out, clean and grease free. All grounds appropriately connected

- Battery is 6 months old Triple A battery. Battery tests fine with multimeter, as well as the rest of the body and grounds

-Positive terminal gets very hot after running for 20 secs. During test drive after motor mounts, RPMS would drop to 0 in neutral. Normal idle when stopped!

- Positive from batt to fuse box gets hot

Have a feeling it's a simple fix... would love to do this myself but have torn it apart almost daily and cannot find solution yet. Any advice is greatly appreciated. Thanks!
 
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Clipsoe

Proven Member
97
23
Apr 22, 2015
Fort Lauderdale, Florida
Well looks clean...my only concern would be not getting anything on the continuity test on the firewall ground. So when you put it on that setting an touch from negative terminal and firewall ground you don't get any tone? Continuity setting on MM should look like a wifi signal
 

1990TSIAWDTALON

Moderator
9,128
4,964
Nov 14, 2013
Independence, Kansas
You can't have enough grounds on these cars. One to the bellhousing/starter one to the fender one to the subframe one to, well, anything you can get to. This sounds like a bad ground issue is why I am saying this.
 

Junzu

Proven Member
127
13
Aug 21, 2021
California
You can't have enough grounds on these cars. One to the bellhousing/starter one to the fender one to the subframe one to, well, anything you can get to. This sounds like a bad ground issue is why I am saying this.
Definitely seems ground related! All grounds are hooked up like they always were but can't seem to find the issue
 

Clipsoe

Proven Member
97
23
Apr 22, 2015
Fort Lauderdale, Florida
I would check that ground wire from the bat to the firewall, and the ground point under it and make sure its clean of rust. Feel along the wire and wiggle it around, maybe its corroded from inside, gotten stiff, or is ripped/ severed. You should definitely be getting a tone as that is a ground point directly from the battery to the firewall. Maybe get a new piece of 4/8 gauge wire and reterminate it and retest.
 

luv2rallye

DSM Wiseman
8,218
1,046
Jun 7, 2003
Minneapolis, Minnesota
I would check that ground wire from the bat to the firewall, and the ground point under it and make sure its clean of rust. Feel along the wire and wiggle it around, maybe its corroded from inside, gotten stiff, or is ripped/ severed. You should definitely be getting a tone as that is a ground point directly from the battery to the firewall. Maybe get a new piece of 4/8 gauge wire and reterminate it and retest.
Agree! Cable from battery negative to firewall is most likely the problem (in fact I can't tell from your pic if it's even there - I only see the frayed cable going to bell housing {which BTW should go under a starter mounting bolt}).

Also all that wire fraying is not good on the battery negative terminal. All cables on BOTH battery positive and negative should be soldered to a ring terminal and that terminal bolted onto the battery terminal. Heat on the positive terminal is caused by a lot of current going through too high a resistance in the positive terminal connection (eg, rust, corrosion, dirt, not tight, etc - too high a resistance may be just 0.1 ohms). You don't have a good connection there either.

Measure voltage drop from the battery post inself (literally) to the wire itself on the terminal when current is flowing. It should be zero or you have problems.
 
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Clipsoe

Proven Member
97
23
Apr 22, 2015
Fort Lauderdale, Florida
Agree! Cable from battery negative to firewall is most likely the problem (in fact I can't tell from your pic if it's even there - I only see the frayed cable going to bell housing {which BTW should go under a starter mounting bolt}). Also all that wire fraying is not good on the battery negative. All cables on BOTH battery positive and negative should be soldered to a ring terminal and that terminal bolted onto the battery terminal.

I was just gonna say the same thing about both the ground to the firewall not looking right, as well as the the wires to the terminals needing to be reterminated. However, instead of soldering and reterminating at the terminals, get some nice terminals like these.

Amazon Terminals
 

Junzu

Proven Member
127
13
Aug 21, 2021
California
Agree! Cable from battery negative to firewall is most likely the problem (in fact I can't tell from your pic if it's even there - I only see the frayed cable going to bell housing {which BTW should go under a starter mounting bolt}). Also all that wire fraying is not good on the battery negative terminal. All cables on BOTH battery positive and negative should be soldered to a ring terminal and that terminal bolted onto the battery terminal. Heat on the positive terminal is caused by a lot of current going through too high a resistance in the positive terminal connection (eg, rust, corrosion, dirt, not tight, etc - too high a resistance may be just 0.1 ohms). You don't have a good connection there either. Measure voltage drop from the battery post inself (literally) to the wire itself on the terminal when current is flowing. It should be zero or you have problems.
Forgive me, vigorous testing shows that the firewall ground is ok. Grounds good. The whole positive wire from batt to fuse box gets hot, therefore only half the terminal gets hot before the heat spreads. Other positive wire is normal...
 

Clipsoe

Proven Member
97
23
Apr 22, 2015
Fort Lauderdale, Florida
When you said "During test drive after motor mounts, RPMS would drop to 0 in neutral. Normal idle when stopped!"
When the RPM's dropped to zero, was it just the gauge cluster going to zero, or did the engine itself drop in RPM's as well?
 

pauleyman

DSM Wiseman
7,975
2,595
Nov 19, 2011
oklahoma city, Oklahoma
That battery looks high. Did you forget to remove a spacer underneath? Is that terminal grounding against the hood? Look for evidence.
 

Junzu

Proven Member
127
13
Aug 21, 2021
California
That battery looks high. Did you forget to remove a spacer underneath? Is that terminal grounding against the hood? Look for evidence.
Thanks for reply! Battery is all good there, and I thought it could be but it occurs when the hood is open

When you said "During test drive after motor mounts, RPMS would drop to 0 in neutral. Normal idle when stopped!"
When the RPM's dropped to zero, was it just the gauge cluster going to zero, or did the engine itself drop in RPM's as well?
Engine too
 

pauleyman

DSM Wiseman
7,975
2,595
Nov 19, 2011
oklahoma city, Oklahoma
Thanks for reply! Battery is all good there, and I thought it could be but it occurs when the hood is open
I would disconnect and start chasing possible shorts. Ign on only may reveal the issue.

Chek everything in close proximity to those mounts. Alternator wire runs right by front motor mount. Make sure you didn't nick it.
 

luv2rallye

DSM Wiseman
8,218
1,046
Jun 7, 2003
Minneapolis, Minnesota
Forgive me, vigorous testing shows that the firewall ground is ok. Grounds good. The whole positive wire from batt to fuse box gets hot, therefore only half the terminal gets hot before the heat spreads. Other positive wire is normal...
Measuring resistance of cables and connections rarely will find problems (especially when the resistance is 0.1 ohm on a battery cable which is still too high - 0.1 ohm with 50 amps running through it, which a starter typically draws, will drop 5v across that resistance and not leave enough voltage for the starter). Measuring voltage drops when current is running through it is the better way to find high resistance connections/cables - not measuring resistance.

Well you've obviously got a short somewhere. Does it get hot with just the key on but engine not running or even with the key off? Here's how to find a short: https://www.dsmtuners.com/threads/f...l-short-or-battery-drain.179481/#post-1496998
 
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Junzu

Proven Member
127
13
Aug 21, 2021
California
I would disconnect and start chasing possible shorts. Ign on only may reveal the issue.

Chek everything in close proximity to those mounts. Alternator wire runs right by front motor mount. Make sure you didn't nick it.
Crap. Didn't even check there I'm hoping I find something there. Will check when I'm off work

Measuring resistance of cables and connections rarely will find problems (especially when the resistance is 0.1 ohm on a battery cable which is still too high - 0.1 ohm with 50 amps running through it, which a starter typically draws, will drop 5v across that resistance and not leave enough voltage for the starter). Measuring voltage drops when current is running through it is the better way to find high resistance connections/cables - not measuring resistance.

Well you've obviously got a short somewhere. Does it get hot with just the key on but engine not running or even with the key off? Here's how to find a short: https://www.dsmtuners.com/threads/f...l-short-or-battery-drain.179481/#post-1496998
Hot when engine is running only. Ignition on only does not create any problems
 

greddy_1700

Proven Member
967
51
Aug 27, 2006
Regina, SK_Canada
Bad voltage regulator in the alternator? I had one fail and when idling the car was putting out 14.x volts, when I tried to accelerate it started climbing to 17-18 volts. Lucky I didnt fry anything...
 

pauleyman

DSM Wiseman
7,975
2,595
Nov 19, 2011
oklahoma city, Oklahoma
New battery or not I would load test that battery also.

Bad voltage regulator in the alternator? I had one fail and when idling the car was putting out 14.x volts, when I tried to accelerate it started climbing to 17-18 volts. Lucky I didnt fry anything...
This is a good point also. Put a voltmeter on it when running and make sure the voltage isn't high.
 

Junzu

Proven Member
127
13
Aug 21, 2021
California
Bad voltage regulator in the alternator? I had one fail and when idling the car was putting out 14.x volts, when I tried to accelerate it started climbing to 17-18 volts. Lucky I didnt fry anything...
Did you test the alternator directly? Google searching about testing an alternator only suggests testing at the battery and determining the status of the alternator via appropriate voltage

Battery 12 volts ignition off. Normal... 14 volts when running... everything checks out there... alternator wire positive exposed in some places but lifting it up away from metal does not make a difference
 
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We're on Boost

Proven Member
1,443
330
Aug 25, 2007
Seattle area, Washington
Your positive battery cable looks terrible right where it gets to the connector on the battery post. It's getting hot. I think you should just replace that whole cable.
Speaking of the connector, would you please shoot us another picture from closeup looking straight down at that end of the + cable so we can see what's going on with the ring, or loop, that is on the end of the cable with a bolt through it? I can't tell from the pic in post #3 but it looks like that ring is broken half off. Something is weird about it. You might need 2 shots. One looking down and angled slightly inboard. Another looking down and angled slightly outboard. Or unbolt it and take a shot of the ring without the bolt in the way.

In post #22 where you say "alternator wire positive exposed in some places". Do you mean bare wire? No insulation on it in some places?
 
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greddy_1700

Proven Member
967
51
Aug 27, 2006
Regina, SK_Canada
Did you test the alternator directly? Google searching about testing an alternator only suggests testing at the battery and determining the status of the alternator via appropriate voltage

Battery 12 volts ignition off. Normal... 14 volts when running... everything checks out there... alternator wire positive exposed in some places but lifting it up away from metal does not make a difference
Thats true for testing the alternator, but not necisarily the voltage regulator. In my case the alternator was fine at idle (~1000rpm), and showed 14.x volts. when I reved the engine up to ~3000 RPM, thats when the voltage started to spike.

Still sounds like the most likely cause is bad wires / ground though. I would inspect and change any and all power and ground cabling that looks suspect at this point. Dont want to mess with overheating electrical that could start the whole car on fire...
 
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