FUSE BOX PROBLEMS!! HELP!!

[jcsr76]

hi, everyone i am new to this site, and was trying to find someone that might be able to help.. my 98 318ti fuse box has a short in number 37, its a 5 amp fuse which controls the cluster lights. everytime i would turn the headlights on, it would blow the fuse, so after about 5 times of doing this, i went to my local auto store and picked up some led lights that plug into the cig lighter, and mouned them on the cluster. it was working fine until 5.0 gave me a ticket, and told me the leds are not legal, so i need to get this problem with the cluster lights fixed. im sure its something simple that im over looking.. can someone help?? thanks.

[John Firestone]

What work and modifications have been done to the car?

[KetteringTi]

Are you 100% SURE it is supposed to be a 5A? I had some fuse issues with my instrument cluster that were solved by a 25A fuse (only needed a 10A, but I only had a 25A available).

[John Firestone]

F37 goes to the light switch, through the dimmer rheostat and only then to the instrument cluster.

The ETM also shows it is 10A. What does the fuse table on the back of the fuse box lid say?

After you confirm it should be 10A, try a 10A fuse but only once and no more than once. If it immediately blows, you have a short somewhere and need to fix that before you try another fuse.

DO NOT replace the fuse should it blow before you fix the problem or you may cause some expensive damage. Also, don't use a bigger fuse than BMW specifies in an attempt to "fix" a short. You may fix it alright by melting the wiring, starting a fire and totalling the car!

Replacing a 10A fuse with a 25A one is just asking for trouble. BMW tries to use as thin of wiring as possible, to save space, weight and money. Some of the fuses just barely protect their wiring.

What mods and work have been done on the car?

[jcsr76]

mods.. aftermarket extrior lights all around, aftermarket sound system, viper alarm, as far as elecrtical goes. the fuse panel sticker calls for a 5a fuse. should i try a 10a? thanks.

[John Firestone]

Very interesting. The three E36/5 ETMs I have looked at all show F37 as 10A. There is, however, some 0.35 mm^2 wire downstream of the fuse which would suggest 5A according to the current Bosch Kraftfahrtechnisches Taschenbuch (Bosch Automotive Handbook), a standard reference for German automotive engineers. That book's recommendation allows a 70 deg C ambient temperature, however, which you might find not find inside the passenger compartment.

With all the things you have added, perhaps you are now over 5A. How many seconds/minutes/hours/days does it take for the fuse blow?

How many watts of aftermarket exterior lighting have you got hooked in to the light switch circuit? How much of the stock lighting remains?

[jcsr76]

about 1 day, then it blows the fues?

[John Firestone]

By a day, do you mean 8-10 hours of driving with the parking lights on?

You need to total up the load on F37 and determine if the extra things you have added to the car should now blow a 5A fuse. If they should, you could try increasing F37 to 7.5A (assuming the original 5A fuse was correct). But make sure you understand what is blowing the fuse. If you substitute a bigger fuse to mask a short, you may have to replace something considerably more expensive and inconvenient than a fuse.

[jcsr76]

i have a 10a in now and it seems to be fine. i have been driving around all day with the lights on, and it hasnt blown the fuse yet, so i guess it was supposed to be a 10 insted of a 5, but the fuse box sticker has a 5a in f37. is it possible it is a misprint?? im hoping for the best, and it it doesnt work, ill take it to the shop. until then i still have the leds.. thank you for your time.