Heater Fuse - PeachParts Mercedes-Benz Forum

gelder · #1 03-06-2009, 10:38 AM

I have an '81 300td. The climate control fuse continues to blow. When the blower is off the system draws 1.54 amps. With the blower on low it draws 6.5 amps. On high it draws 15.84 amps. The blower out of the car with the fan still on the motor it draws 18 amps. With the fan taken off the motor and still 3 amps. with the blower in the car and all the air doors closed it will draw as low as 13.6 amps. Of course with the air in take closed no air blows out. Any ideas? Are there any resistors for the blower? Van

Jeremy5848 · #2 03-06-2009, 11:51 AM

That circuit should have a blue 25 Amp fuse. You current numbers look reasonable. The fuse should not blow until the load gets well over 25 Amps.

Yes, there is a set of blower resistors, in a ventilated metal box on the passenger side inner fender. The resistors are coils of wire, you can look in the box through the vent holes and see them. I've never heard of them burning out or otherwise giving trouble.

gelder · #3 03-06-2009, 12:57 PM

jeremy, Thanks for the reply. My fuse box and manual both say it should have a 16 amp fuse? Van

LNGfish · #4 03-06-2009, 02:15 PM

Roy told me recently when the brushes get worn down it pulls more amps.

This I did not know but he did.

You may want to check to see if they are worn down and the tension. If they are near gone this is your problem I guess. Not sure how long they should be however. I checked my brushes and it wasn't that easy, so be careful.

Maybe oil the motor with some 3 in 1 also.

Good luck.

gelder · #5 03-06-2009, 02:35 PM

Thanks, I have a rebuilt motor and it's amp draw is the same as the old one. Van

Jeremy5848 · #6 03-06-2009, 05:34 PM

I can't find a fuse listing in the owner's manual but the card in the cover of the fuse box of my '85 300D-T (W123, OM617) lists it as 25 Amps. Maybe Mercedes upped the fuse size between '81 and '85?

Ksmailes · #7 03-06-2009, 07:36 PM

Phil at fastlane has an external fuse harness to replace the #8 fuse. I think its around 30 or 40 bucks. You completely bypass the #8 fuse. You'll have to hook it up on the back of the fuse box. Just unhook the battery and cram yourself up under the dash. Takes about 30 minutes.
The stock #8 fuse is inadequate for the demand that the blower motor and a/c circuit put on it. I think this will make it a 25 or 30 amp fuseable like type fuse. I put one on my 82. The fuse box had some evidence that it had gotten hot before (melted). Hope this helps.

gelder · #8 03-07-2009, 11:20 AM

Jeremy. Thanks I put in a 25 amp fuse and presto fixed. I noticed in the mercedes shop manual wiring diagram in super small print it specs a 25 amp fuse. Thanks again. Van

LNGfish · #9 03-07-2009, 03:17 PM

That kit sounds interesting. My 25A fuse for the AC can get warm on HIGH speed to I just run it on AUTO to the fan only goes up the speed 4 instead of speed 5. This seems to really help but the kit sounds slick but not too interested in crawling under the dash, but I would if need be. Question: My 25A has never blown but it gets, I wonder if the Porcelain Fuses are any good? I see Phils sell them but you have to get 20 for like $5 for all 20. Anybody use the 25A blue fuses in this slot, or is the External Kit the way to go?

Are there directions Ks? Glad you posted!

LNGfish · #10 03-07-2009, 03:19 PM

lol, bad typos, sorry.

Ksmailes · #11 03-07-2009, 06:02 PM

No instuctions included. Comes in a MB parts bag. Pretty straight forward just access the back of the fuse block, fish the harness there, and unhook the existing wires and replace with the harness. Just take your time. I think the P/N is on the harness. I'll look and post it to simplify your search.

LNGfish · #12 03-07-2009, 11:25 PM

Was it 126 54 03013 ?

compress ignite · #13 03-08-2009, 04:14 AM

Photos courtesy GSXR:

[you can retrofit this to almost any 123,124,126,201 chassis]