I have been havign trouble with the blower motor function on my CCU. I have decided to wire in a relay on a switch to turn on and off the blower motor. I need to know the fan's amperage draw so I can get a large enough relay and fuse socket(s)

Thanks...

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)

I'm surprised that nobody in the know has responded. I've read the fan current draw on this forum, but cannot recall exactly. If I remember this part correctly, the fuse for this circuit is a 20 amp and it controls the fan and the AC compressor (and maybe some other minor loads). Given that fact, I would think that any portion of the fan circuit should be safe at a 20 amp protection level, even if the compressor is no longer on the same circuit. If you install a modern fuse socket and insert a 20 fuse, and then later decide that you feel better with a smaller fuse, just change the fuse.

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

Ian,

Just curious, why not replace the motor brushes, a little work and about $30.
Or even replace the whole motor with a new one (about $90).

I replaced the motor with a new one on my 83 300SD.
My rationale was that I intend to drive the car until it dies,
which is most likely to be after I do.

This way my car is stock and works as it should.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

The problem lies in the CCU and not the fan unit. I have cobbled together jumper wires to test the fan, and it works just fine. I do not care about a fully functioning CCU as much as defrost!!

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)

The stock fuse is 25 amps. If your motor is good, 12 ga wire and 25A fuse should do it.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

Well, if you are going to use a relay, you'd want to get one that is capable of at least 30A (25A fused circuit for fan as others have stated) on the secondary. Then you'll need to find out what the activation current is on the primary side. Take always hot 12V and put it in series with the switch and a decent resistor that will allow proper activation current to the primary side but also protect from over amperage - maybe put a fuse in there as well that is within tolerance of primary over-amperage. Resistor will need to be able to handle wattage.

As others have pretty much said, it is probably easier to just use a switch.

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

I have used 10 gauge wire with a 30 amp toggle switch. It still gets hot in use. I think a relay would be better........

Ian

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)