Two white fuses, what's the difference...and other electrical questions - PeachParts Mercedes-Benz Forum

pizzachef · #1 03-05-2009, 09:14 PM

I collected a bunch of fuses from somewhere at some point, and now I'm not sure what I have, see pic below. I have two kinds of white fuses, one has a much thinner metal strip than the other, and one's a darker white. Do these have different amperage ratings?

Second question, since I installed foglights on the w115 240D, the fuse that powers the passenger headlamp and both fogs has blown twice. I thought it was just the additional current from the fogs (which were installed in the factory sockets provided on the rear of the headlights, I didn't add any wiring) but now I think I've found the cause...

Tonight when driving home, the headlights and dash lights (I quit using the foglights for now) got really bright and the heater blower got loud. I quickly turned off the blower since I don't want that motor to burn up. The lights stayed bright for a few seconds then went back to normal. Then it happened again for a few seconds and returned to normal and didn't happen again for the rest of the drive. This occurred while driving on the interstate at speed. The engine speed didn't vary much.

I kind of remember this happening before but it was so brief and the time between occurrences is long enough for me to forget about it, but sometimes I have a belt squeal even though the belts feel pretty tight. I don't have a tension gauge to check, but they're not loose enough to be squealing. But the belt squealed earlier tonight, and I'm wondering now if its the alternator belt from the sudden high demand for current from the alternator. And if the lights (and other electrical components) are suddenly drawing more current, maybe that's why my fuse with the three lights on it blows).

Does this sound like a voltage regulator problem? I haven't checked it yet in this car, so I'll probably pull it some time soon to look at it. But if anyone has any other input, I'd appreciate it.

Diesel911 · #2 03-05-2009, 11:57 PM

Forget about the color of the Fuses as different companies make them different colors. Take a good look at the back of the fueses; the Amperage number should be there; just go by that not the color.

Several things could cause a tight belt to slip. Oil on the Belt and a Bearing going bad in side of the Alternator are the 2 I can think of right now.

There would have to be a substantial short circuit before the Alternator would bog down and it would have to be on an electrical circuit where there was no fuse in the circuit.

If you have one in your area Harbor Freight sells adequate inexpensive Digital Volt/Ohm Meters from $3-$9. It is handy to have one.

d71889b · #3 03-06-2009, 12:36 AM

the difference is the metal they are made with

Jeremy5848 · #4 03-06-2009, 01:02 AM

Left–aluminum
Right–copper alloy

The copper allow is preferred; both metals tarnish with age and exposure but the aluminum forms aluminum oxide, which is a pretty good insulator (or at best a semiconductor).

Diesel911 · #5 03-06-2009, 09:59 AM

Members also say that the Fuses with a plastic body sometimes melt when the fues gets hot.

pawoSD · #6 03-06-2009, 10:11 AM

If the one on the left is plastic, toss it. Only the ceramic fuses should be used. Since they cost about $.50 for a set of 10....there's no excuse to not use the better kind

pizzachef · #7 03-07-2009, 10:12 AM

Thanks for the feedback, I didn't know that about the plastic fuses, I'll look into my fuse collection and weed out the plastic ones.
The back of both of those fuses has a tiny number 8 on them, I hadn't seen that before. Also I have a green fuse and a blue fuse that both have a 16, so I'll quit paying attention to the color and more attention to the actual amp rating

Diesel911 · #8 03-07-2009, 11:07 AM

Quote:

Originally Posted by pizzachef

Thanks for the feedback, I didn't know that about the plastic fuses, I'll look into my fuse collection and weed out the plastic ones.
The back of both of those fuses has a tiny number 8 on them, I hadn't seen that before. Also I have a green fuse and a blue fuse that both have a 16, so I'll quit paying attention to the color and more attention to the actual amp rating

I am not sure what goes on with the plastic bodied fuses. I am guessing that that part of the heat that would go into melting the metal strip on the fuse and protecting you circuit ends up being used to melt the plastic. A few members have reported that the plastic melted but the circuit was not protected.
When I go to the Junk Yard I like to also get a bunch of Fuses.

Looking at this Fuse while it was still in the Fuse Box; it looked like a good Fuse. But as you see in the pic; when the fuse is pulled out this fuse is no good.
If something is not working and you think it is a Fues. Take a little extra time and pull the Fuse out and check it. (The above fuse was one of the 2 Fuse that go to the Electric Windows that had stopped working.)

compu_85 · #9 03-07-2009, 12:24 PM

Quote:

Originally Posted by pawoSD

Since they cost about $.50 for a set of 10....there's no excuse to not use the better kind

Where can I buy the correct ones?

-Jason

Diesel911 · #10 03-07-2009, 02:21 PM

Quote:

Originally Posted by compu_85

Where can I buy the correct ones?

-Jason

The regular Auto Part Stores sell sets but you will get some Fuses you do not need and not get some you do need. Also the tend to supply only a few of the higher amperage Fuses.

It maybe that Phil or Fastlane has a set of Fuses just for your particular model that will only have the Fuses you need.

You might want to look at the chart in the Lid of your Fuse Box and write a list of the Amperage Sizes that you need.

Don't forget an extra Strip Fuse on the Glow Plug Relay or I believe a Member said there is also a similar but Lower amp Strip Fuse for the Heater Blower Motor.

bgkast · #11 03-07-2009, 02:42 PM

I've never been able to find new ceramic fuses. I just got a good collection of them from a junkyard car. When they blow you can transfer the metal strip over from a plastic one.