Re: Loose battery terminal caused odd dysfunction w/89 Cressida - what am I seeing?
- From: "CharlesGrozny" <n5hsr@xxxxxxxxxxx>
- Date: Wed, 15 Dec 2010 13:07:08 -0600
"muzician21" <muzician21@xxxxxxxxx> wrote in message news:5c1b4e7d-de30-4353-92cf-2fb7d20b1c32@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Got in my '89 Cressida and noticed the power windows weren't working.
All out at the same time.
Checked various fuses, found none that looked burned out. Then I
noticed another issue - the power door locks worked to lock, but not
to unlock. The driver door and I assume the passenger door could be
manually unlocked of course but didn't trigger the others to unlock as
is normal operation.
Then I noticed the clock was wrong, which only happens if the power if
interrupted. So, I checked the battery terminals and found apparently
I'd neglected to cinch one down and tighten it when last needing to
disconnect. It was on but with a loose fit. Re-seating and tightening
made all the above issues disappear.
So what did I witness? If there was enough connection to run the car,
why would some of the accessories behave oddly or be non-functional as
What you're seeing is Ohm's Law at work. It must take slightly MORE power to unlock than lock, for instance. The power windows probably use a lot more power. A loose fitting causes a higher voltage drop at the source. Also burns up some of the available amperage. What moves the locks and the windows is volts times amps, the very thing that's getting consumed in the loose fitting. Volts x amps = watts. The total amount of current is the voltage divided by the total resistance. You're adding a lot to that resistance with the loose fitting. Current = Volts divided by ohms. You've only got 13.8 volts to start with. If you raise the resistance (I.e. loose connection) you lower the current available for other things. Instead of most of the 13.8 volts getting to the locks, windows, etc, more of it is getting burned up at the poor connection.
That's why corroded battery terminals are such a problem, too. Again, you're adding to the total resistance, and using up some of the voltage, thus cutting what's available to the rest of the circuit. Good clean solid contacts are important, even in this day of electronic everything.
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