I have an '84 300TD with several electrical issues which I intend to sort out. They might be one issue, but I suspect more than one at play.

1. My horn/reverse lights' fuse blows -- and I can't get the vehicle inspected. I think it is fuse #14.
2. The battery slowly drains over 24 hours.

I have had problem #1 a lot longer than problem #2.
Can anyone direct me to a good wiring diagram for this vehicle? A downloadable full service manual would be even better!
I think I may have a Bently Manual somewhere in storage (across town); I'll have to try to dig that out.

I am going to go out and do a voltage test as I pull fuses, take some notes, and see what that shows up.
Any and all advise is greatly appreciated.

peace and grease,
-Steve

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1984 300TD wagon with heated dual-tank WVO.

http://www.startekinfo.com/StarTek/doclist.jsp

Sixto
87 300D

Thanks Sixto for the link -- but it did not work for me. Do I need to register and sign in to that site first?

I spent an hour with a multimeter and got some good info and solved the second problem.
There was a 7.6amp draw with no Key. Going through the fuses made #2 look like the culprit. Turns out it is my crappy old aftermarket radio... which had stopped working some time ago. Removed the radio, and now there is no voltage draw with no key -- problem solved.
YEY!
If I got it right, now I no longer need to unplug the battery at night.

Back then to problem #1 -- no horn, no reverse lights. Looking at the fuse box, fuse #14 is Lord over many diverse things!
I know that the heater control valve was malfunctioning at some point, but the no horn problem pre-dates the valve problem. I went ahead and disconnected the valve and my broken antenna.
I am still trying to sort it all out, but I have a good start.

Your input would be very helpful.
THanks!
-Steve

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1984 300TD wagon with heated dual-tank WVO.

http://www.startekinfo.com -> MB Workshop Resources -> Service Manual Library CD/DVD -> Model 123 Service Library -> 123 Disc 2 -> 300TD '84 -> Continue -> Electrical Troubleshooting Manual -> Wiring Diagram

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/ETM/83_300.pdf

Sixto
87 300D

Does the fuse blow immediately? Do you know how to check for a short circuit by using a 12 volt lamp on the load side of the fuse?

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

If you have an Automatic Transmission the Neutral Safety Switch doubles as the Switch for the Backup Lights.

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84 300D, 82 Volvo 244Gl Diesel

Thanks to all of you for your help.
I found my final two electrical shorts.
#1 was in the horn wires for the passenger-side horn. The wires had rubbed against (I think) the A/C compressor, some of the sheathing was exposed, and the wires were touching at the short. So when ever the horn was pressed the fuse would blow.
#2 was in the passenger-side tail light. the bulb's housing, which also doubles as the negative ground had come loose. These are somewhat flimsy and different from all the Japanese and Domestic ones I have seen.... It had come in contact with the positive lead, and shorted when the car was put in reverse.

I bought a new horn set, just to be safe, and the car passed inspection for the first time in two years. YEA!!!

peace and grease,
-Steve

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1984 300TD wagon with heated dual-tank WVO.

Thanks for the link too.