Restored my tailgate wiring harness this weekend. (For those wondering, I added splices to the orginal wire and ran 'em through the hinges.) Everything more or less works now, but I have one problem:

Whenever I turn on the headlights, the fuse for the license plate lights and the left tail light blows.

I think the new bulbs I put in the plate lights (Sylvania 6411) are too big. I notice that these are 10 watts, the originals are 5. Would that blow the fuse? What's the right bulb, anyway?

With the bulbs removed the fuse is fine.

I have good continuity and no bare wire in the splices I put in the harness.

Can anyone help diagnose?

(A bonus question: Where can I find those tiny bayonet style bulbs that illuminate the instrument panel?)

Thanks as usual,

Steve M.

Raleigh, N.C.

73 145
84 240

Steve,

I was thumbing through my new 240 Bentley manual tonight. This manual has a whole section on ground locations and when I saw the picture of taillight grounding, your problem came to mind.

Make sure that you have a very secure ground point for the taillights and plate light circuits. Some very odd electrical problems in cars can be attributed to poor grounding. It could be that one of the grounds is open or week, in which case the current for the taillights finds another path causing the weird situation you describe. I would not expect the hinges to provide a good ground. It is probably best if you the ground is attached directly to the car body and not the tailgate.

Dan

Steve,

As Dan has said. You will get an in rush current on the light illumination (negligable), it is worse for AC motors items like you refridgerator, hair dryer etc. in your house . We need to know the value of the fuse and other stuff on the line (what else goes out when the fuse blows or from schematic). One thing you can do is get a DVM with 20 amp prefered current capability and connect it (in series) where the fuse goes in the fuse box. Pull all the bulbs first then readd and repower/light them one at a time and keep an eye on the meter until you exceed the fuse value then you will know the problem or you have the fuse lines loaded to much. If you go for all bulbs at once and exceed the 20 amp of the meter you will blow the fuse in the meter. You can use math (E=IR, I2R) to calculate the loads also as Dan did in liu of the meter but need to know the loads. You can also use a clamp on DC amp meter .

Greg Bodner
1970 1800E

The 10 Watt bulbs will draw about 0.7 Amps each (14V * 0.7A = 9.8W). The 5 Watt bulbs will draw about 0.35 Amps. Don't know what else is on the circuit, or what size fuse is blowing, but these are pretty small currents.

The current in light bulbs will be consideraby higher for a split second until it warms up. The resistance goes up with heat, which means the current goes down. This is why the lights in your house most oten blow when you first turn them on. Are the fuse regular automotive fuses? These should be able to take the higher current.

The "idiot light bulbs" in the 240 instrument panel are small bayonett bulbs. Do you know if these are the same. I can send you some. Just replaced the Instrument panel in my 240 today. The Spedo now works and I added tach.

Best of luck.

Dan

Thanks. These are the plastic euro-fuses -- supposed to be a 5 amp. I blew an 8 and whatever comes next (14? 16?). Nothing is on the circuit but the lights -- unless it's shorting out somewhere, I guess.

The instrument panel bulbs are different from the 240 panel bulbs. I can't find them in the auto stores or Radio Shack.

I hate electricity.

Steve M.