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Fuse box terminal very hot


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Limelight
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Nov 25, 2009, 1:58 AM

Post #1 of 4 (2849 views)
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Fuse box terminal very hot Sign In

Electrical problem
1994 Oldsmobile Cutlass Supreme 6 cyl Front Wheel Drive Automatic 104745 miles

Hi i have encountered a problem with my fuse box terminal. It gets so hot that it melted the plastic covering. Also my battery gauge is very low and sometimes goes so low my gauges and lights cut off when idling.My abs light is always on (abs fuse is in that fuse box.) I took it to a shop and they checked the alternator and battery and said they were fine but said my fuse box was melting down and they tightened the bolt and the ABS Light went off and my battery gauge was fine. My problems started to reoccur recently and the bolt is as tight as it can get and i checked the fuse box and there is absolutely nothing melted and all seems fine with it. Could it be a shorted wire or something else? Thanks again.


(This post was edited by Limelight on Nov 25, 2009, 1:59 AM)


DanD
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Nov 25, 2009, 7:31 AM

Post #2 of 4 (2838 views)
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Re: Fuse box terminal very hot [In reply to] Sign In

Heat being generated on an electrical circuit is caused by excessive current flow or high resistance.
Excessive current flow can be caused by having too many after market devices (Stereo amplifier, navigation equipment Cell phone charger, ect) connected to the circuit. Or a factory installed device that is beginning to fail drawing to much amperage.
High resistance is caused by corroded connections, wiring or again a device that is beginning to fail and is restricting normal current flow.
You’ll or someone will have to isolate the individual circuits, leaving this fuse panel and test them for current flow/draw. You may find something, like a heater blower motor that is drawing twice its normal amperage.
To test for excessive resistance; I would again isolate each circuit and then perform voltage drop test across each one; including the power feed into the fuse panel.
There could be some form of corrosion that has formed inside a connection that you cannot actually see. But by performing voltage drop tests; you should be able to pin point exactly what section of wire, device or connection that is at fault.
No it’s not a 10 minute job and you will need someone with a bit of experience, to properly perform the tests.
Any more then a ¼ volt, voltage drop across any circuit, is considered high.

Dan.

Canadian "EH"






Limelight
New User

Nov 25, 2009, 9:19 AM

Post #3 of 4 (2833 views)
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Re: Fuse box terminal very hot [In reply to] Sign In

Thank you for the quick response. Luckily there isn't much going on in this fuse box. Everything to my knowledge in the box works as it should and no other extra fuses or devices are installed. The fuses are all fine as well. I polished the connectors and some of the solder that was corroded around it and tightened the bolt nice and snug and my battery level goes up to normal except sometimes when i start the car the ABS light will pop up sometimes not. The terminal is still hot to the touch.

Fuses
1. 60 AMP ABS
2. 30 AMP Headlamp Circuit Breaker
3. 40 AMP Ignition Switch
4. 40 AMP Ignition Switch
5. Not used
6. Not used
7. Not used
8. 15 AMP Horn
9. 25 AMP Park Lamp
10. 10 AMP Fog Lamps
11. Not used
12. Not used
13. Not used

Relays
14. Horn
15. Fog Lamps
16. ABS

Do you think the shortage is more likely in the fuse box or away? I happen to have to tools to test the wires but not on hand.


DanD
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Nov 25, 2009, 1:21 PM

Post #4 of 4 (2812 views)
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Re: Fuse box terminal very hot [In reply to] Sign In


Quote
Do you think the shortage is more likely in the fuse box or away?

That's like asking the age-old question of, what came first the chicken or the egg. From here at my key board I have no idea.
Even though all of the devices that are protected by the fuses in this panel are functioning; doesn’t mean that one or more of them are not drawing excessive amperage.
Although I am leaning toward a high resistance, as being the problem; a resistance problem that will only be detectable while whatever circuit is under load.
That’s why I suggest using the voltage drop method of testing the circuits.
For example; let’s say there is a connector that only one third of the contact area is making a good connection.
If you were to use an ohmmeter across this connector; you would likely get a very low resistance reading, which would make you think it is good.
Connect a voltmeter from negative to any part of that circuit; you’ll likely get very close to source voltage, which again makes it look good.
But if you were to connect a voltmeter to battery positive, then to the far side of the suspect connector and then energize (turn on) whatever is being powered by that circuit; you may see a 2 or 3 volt reading on the meter. In other words; a 2 or 3 volt, voltage drop; that would be way to high and could cause that connection to get hot; even though the devise is working “normally”.
Here’s a basic drawing of how to connect a voltmeter to perform a voltage drop test on a circuit’s wiring and connections.

With the circuit turned off, the voltmeter will (should) read zero; turn the circuit on and you should not see anymore then ¼ of a volt maximum.
If you do see higher then that, begin moving the voltmeter lead back towards the power source (battery). Once the voltage goes back down below this ¼ volt; you’ve found the corroded connection or wire. It’s between the last two points of where the meter’s lead was connected.
Dan.

Canadian "EH"








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