Anyone have a schematic for under the fuse box? or done any work there? I have a bunch of electrical that does not work, power seats etc. that I do not care about. Now the blower motor for the heater went and started blowing fuses. So I got a new blower, and while I was standing there watching the fuse, I noticed that a bunch of the wires, 4 that I could see, have the insulation melted from them.
Can I fix this? and is this the cause of all my issues? I do not know, But any advice would be great.
Car is at almost 450K. And if I can get 4-5 more years from her it will have passed all my kids through learning to drive! and out of the house.

Thanks

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83 300SD Dark Silver Dark brown inside

hope these will help

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The question regarding the wires that have melted the insulation is as follows:

Are these wires used for running the blower motor? You mention four of them, which would likely include some other circuit other than the blower motor.

The blower motor is noted for demanding more current as it ages. This current can get to a point where it will start to melt the plastic fuse holders or possibly melt the wiring if it gets severe enough. You would think the fuse would trip prior to such events, but, apparently, the tolerancing in the fuses allows a wide range of current flow. The fuse works on an absolute short circuit but isn't so good with elevated current on a proper circuit.

Thank you, I will start tomorrow, and see if I can find out what melted. I am concerned, and also feel like I need to find a want to look under the dash for any damage.
Really do not want my girls driving a fire ball...
But do not want to buy another car,
Safety first.
I will let you know what I find.
Thanks
Doug

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83 300SD Dark Silver Dark brown inside

What do relay B and relay F go to? those are the wires that are melted. And There is what appears to be a hot lug in the bottom of the box, under the fuse and relay panel.
What size of wire is required to run 30A for the heater, I am going to search for that external fuse mod now.
Thanks
Doug

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83 300SD Dark Silver Dark brown inside

B is the auxiliary fan.

F is the power window relay.

They are unrelated.


The power window relay gets very heavy current via a 4mm red wire that is hot at all times. This might be the hot terminal that you refer in the bottom of the fuse box. It does not appear that the relay has any protection from overcurrent.

I intend to eliminate the power window relay permanently on the SD because of this danger and because there is no reason why the windows cannot operate at all times. The power window relay only serves to close the circuit to the power window fuses when the key is in the run position. If the relay is removed and sockets 1 and 3 are permanently jumped, the windows will always operate.

Regarding wiring for the blower:

It gets fed via the 25A fuse number 11. M/B uses 2.5mm wire for the blower. This size is slightly larger than 14 gauge and slightly smaller than 12 gauge. Therefore, 12 gauge is preferred.

So I got a bottle of that liquid tape in a bottle, and covered the exposed wires. I then replaced the fuse with a 30A, external.
Now that I got it back together the battery is draining overnight, this is new, and I can not see anything that I did to cause this.
I can only find a couple of fuses that hare hot with the key off, I have pulled those, and will check on Saturday when I get back from a quick trip to Idaho.

I will have to check the power windows and make sure they still work also,

thanks

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83 300SD Dark Silver Dark brown inside

doug, the tool you will want for this kind of work is a multimeter. with the ammeter part you can test circuits for slow drain; with the ohmmeter part you can test wiring for accumulated resistance; with the voltmeter part you can test potentials around the car to see if they've been degraded by dirty connections. seriously.