Fuse Keeps Blowing
12-30-2007, 07:00 PM
#1
Three Wheelin'
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Fuse Keeps Blowing
I did a search on the topic and didnt really find anything too useful, just a few people with other fuses blowing. My #12 fuse keeps blowing. It as an 8 amp and it controls the guage lights, ashtray light, glovebox light, and liscense plate lights. For hours today I went through all the liscense plate light wires and they are fine, I also cleaned a ground in the back. I took out my glove box light and checked the wires, I also cleaned a ground behind the glove box. I havnt taken the dash apart yet, but is the ashtray light the light on the headliner? I ask this because the light on the headliner works even without a fuse in the number 12 position at all? Any other suggestions, or am I missing something obvious?
My car is an 84' 944.
My car is an 84' 944.
12-30-2007, 07:20 PM
#2
Nordschleife Master
I did a search on the topic and didnt really find anything too useful, just a few people with other fuses blowing. My #12 fuse keeps blowing. It as an 8 amp and it controls the guage lights, ashtray light, glovebox light, and liscense plate lights. For hours today I went through all the liscense plate light wires and they are fine, I also cleaned a ground in the back. I took out my glove box light and checked the wires, I also cleaned a ground behind the glove box. I havnt taken the dash apart yet, but is the ashtray light the light on the headliner? I ask this because the light on the headliner works even without a fuse in the number 12 position at all? Any other suggestions, or am I missing something obvious?
My car is an 84' 944.
My car is an 84' 944.
12-30-2007, 07:58 PM
#4
Three Wheelin'
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The fuse blows immediatly, this problem started last night. Last night it took maybe 5 mins for the fuse to blow, now it is instantaneously. Nothing is plugged into the cig lighter. I thought it may have been my radio but I pulled the radio and it still blows the fuse immediatly.
12-30-2007, 08:01 PM
#5
Under the Radar
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Check the overhead light. I had a similar problem. The $8 dome light broke inside and was shorting the circuit to the body. That would instantly trip a fuse.
Try that before you pull half the dash apart like I did.
Try that before you pull half the dash apart like I did.
12-30-2007, 08:10 PM
#7
Burning Brakes
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Is it a direct short or over current? Check with a meter. A direct short will be 0 ohm to ground. Over current (or partial short) will be a resistance. You're going to get some resistance simply because of the light bulbs.
Best way to track down an over current is to start pulling light bulbs. After each one, check the line to see the short (with a meter).
Best way to track down an over current is to start pulling light bulbs. After each one, check the line to see the short (with a meter).
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12-30-2007, 08:21 PM
#9
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Check out these wiring diagrams in Volume 4:
http://www.cannell.co.uk/Manuals.htm
Once you find out what's on the circuit for the fuse that's blowing you can start to isolate the problem (short) by disconnecting circuit loads (bulbs). The 12V wire for the gauge lights goes through the dimmer pot on the dash. I'd disconnect the dimmer pot to see if the fuse survives. Also disconnect the lighter using the procedure to remove the clock as shown on Clark's garage. Removing the license plate bulbs is also worth a try.
http://www.cannell.co.uk/Manuals.htm
Once you find out what's on the circuit for the fuse that's blowing you can start to isolate the problem (short) by disconnecting circuit loads (bulbs). The 12V wire for the gauge lights goes through the dimmer pot on the dash. I'd disconnect the dimmer pot to see if the fuse survives. Also disconnect the lighter using the procedure to remove the clock as shown on Clark's garage. Removing the license plate bulbs is also worth a try.
12-30-2007, 08:55 PM
#12
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I meant dimmer pot (as in potentiometer). On later cars there's a brightness adjustment wheel for the gauge lights. Does your car have a way to adjust the gauge light brightness? If so, this would be the thing to disconnect.
12-30-2007, 11:34 PM
#13
A real easy way to diagnose this is ( it sounds like a dead short) take a test light and put it in place of the fuse. the light will light up because one side is power and the other is a dead short. Start messing with connections, wires ETC till the light goes off, and you have found your short.
HTH
Mark
HTH
Mark
12-31-2007, 01:22 AM
#14
Three Wheelin'
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JayVee, ya sorry about that, yes the early cars do have a dimmer but you cannot disconect just that as the light switch and dimmer is the same connector. Thanks for the replies guys, I guess I will just have to work on this. God I hate electrical problems, they are truely the worst...
12-31-2007, 11:57 AM
#15
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Here's some more info that may help. Pages 66 and 69 of Volume 4 show the circuit for fuse #12. At the top of page 66, fuse #12 is shown feeding two branches, one that goes to F13 and one that goes to G4. If you could disconnect one of these branches right under the fuse box then you could isolate the problem to either the connection to the license plate lights or the connection to the interior lights. Does anyone know if these connections from fuse #12 to F13 and G4 are just wires under the fuse box?