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Old 08-11-2021, 01:29 PM
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Fuse mystery on ‘76 240D W115

Hello, On my W115 1976 240D there are three under-hood double-fuse fuse boxes (separate from the main fuse box). There are two double-fuse boxes on the left-hand (driver-side) fender, one black plastic and one brown metal. Over on the right-hand side (pass side), there is another double-fuse box, black plastic, basically mounted to the firewall. I would like to know the proper amperage on all 6 of these. And, I am trouble-shooting the auxiliary/condenser fan which doesn’t come on. I want to see if one of these fuses is for it. Many, many thanks for the help.

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Old 08-11-2021, 03:10 PM
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All of these are for options that did not appear on the rest of the world cars. Air conditioning is using one set of two, power windows and foglights could be the others.

The best way I have found to see what these aux fuses go to is to first check the fuses. Then clean and check the contacts the fuses fit into as these will tarnish and reduce electrical flow to zero. After that it is just a matter of tracking down the wiring which is usually easy on these cars.

On the aux fan the place to start is by unplugging the fan and hitting the two contacts with a 12 volt power source. The brown wire is negative. If the fan runs then go on to the high pressure A/C switch which is located on your dryer (usually) Turn on your A/C and see if the switch passes voltage from one pole to the next. If not it's your high pressure switch. And it usually is.

If you fan fails to run after being directly connected to voltage then check the connection to the fan and see if 12 volts is being supplied to the fan. If it is and the fan will not run upon direct connection then you have found a bad fan.

Just keep checking the wiring with the car running and the A/C on. Eventually you will find where the voltage stops coming through.
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Old 08-11-2021, 03:51 PM
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Thank you for the guidance. I don’t have power windows, sunroof, or fog lamps. Just A/C. I’ll take a shot at tracing wires, but most are bundled at some point. Amperages are unknown also. Maybe I could measure the current passing through, the fan for example, and figure it out from there. Thanks again!
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Old 08-11-2021, 09:58 PM
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The double fuse slightly to the right of center on the firewall should be for the AC blower motor, not the heater blower motor.

Nice cars 76 240D, mine was AC, manual transmission. It just wouldn't quit, bought as an engine basket case with pieces in the trunk, put it together and it ran really well.
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Old 08-12-2021, 09:45 AM
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This is very helpful. Thanks.
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Old 08-12-2021, 05:29 PM
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Quote:
Originally Posted by 1simpson@bellsouth.net View Post
Thank you for the guidance. I don’t have power windows, sunroof, or fog lamps. Just A/C. I’ll take a shot at tracing wires, but most are bundled at some point. Amperages are unknown also. Maybe I could measure the current passing through, the fan for example, and figure it out from there. Thanks again!
The different colors of the fuses will tell you their amps. This is provided the correct fuses are in there and a previous owner didn't just throw in what ever they had on hand.

You should have white, blue and red. Sometimes there are also black ones. I can't remember the amps vs. colors, hopefully some one will chime in with the info.

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