Fuse fine but tests bad ??


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Old 10-25-09, 02:35 PM
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Fuse fine but tests bad ??

I was troubleshooting a minor problem with my car and came across a fuse that behaved strangely. When I turn the ACC on and use my tester, the light on the tester does not come on as it should with a good fuse. I placed my tester on both sides of the fuse. I took the fuse out and saw that the wire inside the glass was intact. I tested the fuse with my ohm meter and it showed continuity, which means it did not blow. Any explanation why my tester does not light up with this fuse ? I tried the tester on the rest of the fuses and the light comes on each time. This particular fuse can not possibly be causing my car trouble, but I'm still interested in knowing the logic behind that.
 
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Old 10-25-09, 02:46 PM
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swap that fuse with another of the same rating & retest
 
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Old 10-25-09, 06:17 PM
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Does the light light up on one side of the fuse?
 
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Old 10-25-09, 06:27 PM
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if you put the tester on both sides of the fuse at the same time, unless the fuse is blown and there is power on to the fuse, you will not read anything.

Pull the fuse and test the terminals underneath. Check to a known good ground. Note, there are not as many good grounding points in a car as one might think.

Find a spot that allows for a reading from other points and then maintain the one point and move the other to the fuse or fuse holder.
'
when you have that figured out, come on back and tell us what happened.
 
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Old 10-26-09, 12:32 PM
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I know better. I put the tester on each side one at a tme- not on both sides at the same time. Today I found something interesting: I noticed that this 15A fuse blows if I press the brake pedal for an extended period of time, like at a long traffic light. I also noticed that the brake light inside the car behind the back seat will not go out immediately after I let go of the brake pedal. It stays on for a bit and then goes out on its own. The outside rear brake lights work fine. Could this be causing the fuse to blow ? This is a big problem because when this fuse blows and I put the car in Park, I won't be able to shift gears again even though the car starts and runs fine. Thank you.
 
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Old 10-26-09, 01:35 PM
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If the fuse blows, simply unlock the steering column without switching the car on, put the gear selector in neutral, and then start the car. The fuse is for the selonoid that locks the shifter in park, once it is out of park you can shift like you always do. As far as the fuse blowing, what else does it feed? Are the brake lights on this fuse? I would be looking for a loose connection or bad bulb on the brake lights, if they are on that circuit.
 
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Old 10-27-09, 07:53 AM
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Yes, the brake lights are on this fuse. I removed the inside brake light bulb behind the back seat for now to see if the fuse still blows as I suspect it's not good. I will test the car for a couple of days and see. Thank you for the responses.
 
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Old 10-28-09, 05:51 PM
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I noticed that when I hit the brake pedal the display lights come on at the same time and they will go off when I let go of the pedal. Clearly, this is the reason the fuse kept blowing - too much current flows through it. I guess one or more wire of the display are touching the brake light wires ?? Can someone offer a good method to troubleshoot this problem ? Can the brake light switch be causing this ?
 
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Old 10-28-09, 06:09 PM
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A wiring diagram would help a lot.
My thoughts are this:
The only reasonable path that I can think of from the brake lights to the display (I assume you mean the lights in the instrument panel) lights, is from the brake light circuit to the parking light circuit (usually the intrument lights come on with parking lights). The place where I would think about these circuits crossing paths is a rear bulb socket, esp if the car uses dual filament bulbs, the brake and parking (tail) light share the same socket. What I am thinking is that power is jumping (called backfeeding) from the brake light circuit to the parking light circuit which is putting power to the dash lights, and if you check possibly the other lights on the parking light circuit, such as the front marker lights). Could be as easy as a problem with a bulb or even installation of a bulb. Probably nothing to do with the center stop lamp. I'd remove the rear brake/tail light bulbs and see if the problem is gone. Of course don't leave the driveway without them, just test in the driveway and go from there.
Gilly
 
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Old 10-29-09, 04:05 AM
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A shorted bulb may cause your problems or bad ground at light.
 
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Old 11-03-09, 09:00 AM
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You guys are awesome ! Thank you ! I found the problem. One of the back light bulbs, which is also a tail light bulb, had the two solder points on the bottom touching. I guess the very hot sun here along with normal usage melted the joints to a point where they were actually making contact. Replacing the bulb saved the day - and my wallet. Thanks again for your time.
 
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Old 11-03-09, 09:13 AM
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Good deal, as we say here in WI
 
 

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