Fuse #6

[hands_aus]

I was taking my 250SL for a short drive after installing the new ignition switch.

Without prolonged cranking, it just wouldn't start.
Once warmed up it was easy to restart.

I keep 2 small led test lights on the cold start relays. (250sls are wired differently to the 230sl and 280sl)
Neither had 12V on them.

After looking at the wiring diagram I found that the only things on that fuse, #6 (25 amp) are the heater fan and the cold start relays.
The heater fan was not working (it normally does).

I looked at the fuse.
It looked to be OK.

Still no 12V at the test lights.

I removed the fuse and sure enough the terminals on the fuse and the fuse holder were completely encrusted to the point of no continuity.

I used wet and dry to clean the fuse and the fuse holder and after installing the fuse, the car almost jumped off the ground when I turned the key.

The rest of the fuses have been checked.

Something so small creating such a problem.

[mdsalemi]

Seems that regular maintenance of the fuse box is in order.

You can buy, at electrical supply houses, a small tool which is a soldering aid: it is a wire brush like a small paint brush, specifically designed for cleaning electrical contacts.

http://www.all-spec.com/products/SH20G.html?gclid=CO3gvqmtyrcCFc9FMgoddXkAaw

That's only one example from one manufacturer.  They are good to have in the toolbox of someone owning a car whose age is measured in decades...perfect for cleaning all contacts, including those at the fusebox.

[71Beige280SL]

I have had the same issue on corroded fuses. Michael's solution is much more elegant than the sandpaper I have used. I am afraid of using steel wool on the fuse box contacts for fear that the steel wool shavings will reek havoc on the electrical connections. I may be overly cautious here.

[mdsalemi]

for fear that the steel wool shavings will reek havoc on the electrical connections. I may be overly cautious here.

Most of these soldering tools, for your concerns noted, have STAINLESS STEEL bristles; they won't rust and won't fall off.  The "havoc" you are cautioned with is real. A little shard of steel wool where you don't want it isn't good. Sandpaper might leave some grit behind--a little brush is just what you need...

...and in light of all recent talk about parts, etc. the astute will note that this is a very inexpensive solution to have around in your tool box! 

I've noted it before: be wary of spray "contact cleaner".  Most of them (not all, but most) will dissolve and crumble plastic in a heartbeat.

[66andBlue]

...  Most of them (not all, but most) will dissolve and crumble plastic in a heartbeat.

One of those that will not dissolve plastic but do wonders to your electrical contacts is the DeoxIT series:
http://www.caig.com/
I have used it on the infamous rheostat in the instrument center cluster with excellent success.
The Navy buys gallons of that stuff to keep the old ship instruments running.

[mdsalemi]

One of those that will not dissolve plastic but do wonders to your electrical contacts is the DeoxIT series:
http://www.caig.com/

Great find, thanks Alfred! Any sources for retail? I guess you can get it direct with minimum order, but helpful to know of any other sources.

They have a great selection of products including one we should all have...cell phone contact cleaner!  Saw the 2 people ahead of me at the Apple store suffering contact issues!

(I have a good selection of "will dissolve all plastic" contact cleaners, and probably time to get a good one that won't!!)

[Benz Dr.]

I can't remember seeing this problem but it might be a good idea to give us a short list of the more popular products that are known to cause trouble.

[66andBlue]

Michael,
since the company is in my back yard I just went there and bought a small can - lasts forever - DeoxIT®, #DN5S-6N.
Here is a list of retail sources from their web site:
http://store.caig.com/s.nl/sc.15/category.295/.f
For direct sales the minimum order is $25.

[mdsalemi]

I can't remember seeing this problem but it might be a good idea to give us a short list of the more popular products that are known to cause trouble.

One of them I had was CRC Contact Cleaner 2000, no good on plastic.  I did have another CRC product that did soften some hard plastics, but not too bad.  Some are labeled "Safe for All Plastics" and some "Safe for most plastics"; Just be careful what you are buying and read the label. I no longer have these and will try and get that CAIG product.

[71Beige280SL]

I just ordered All-Spec soldering brush. Interestingly, because my order was below $25, they charged me a service charge of $8.00. 2 x what the brush cost. Still cheap! 

[Cees Klumper]

X2 on the fuse contacts; I've battled bad contacts problems in my El Camino and, last weekend, my trailer. No problems with the Pagoda (touch wood) so far though. Thanks for the tip Alfred on that DeoxIt product, it's also available in Europe, a quick search reveals!

[wwheeler]

Once the corrosion is gone, be sure to check the cover seal. Maybe it is leaking and allowed corrosion?

I have always used dielectric grease on the fuse contacts. Yes, dielectric indicates non conducting. But the metal makes contact through the grease allowing the grease to form a barrier around the contact area. It has been on my fuses for over 6 years and no trouble or sign of it. I still try to twist the fuses once a year to renew a good contact. I use dielectric on most terminals (including the battery), contacts etc. Never had corrosion when it is there.