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#1
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Is there any way to test the rear-window defroster in my 1984 W123 300D
Funola has expressed interest in coming up here, giving me $$$, and pulling the glass himself if I can get it to work. This sounds like the perfect way to get lazy money, but I need to test it. How do I do that?
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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes 1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod 2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die." |
#2
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Answer
Pre dawn is best for this test.
Jump it with 12V for 2-5 seconds with a 16 amp (RED) fuse in circuit. As long as it is not in direct sun load, an Infrared Thermometer should tell you if it is working. .
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ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
#3
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I am an electric idiot... can you tell me how to jump it? The car is not startable, so I'd need to just do this right off the battery -- I assume that that is OK?
__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes 1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod 2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die." |
#4
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I'd prefer if you measure the current. set DVM on the highest scale (more than2 amps). remove fuse 10 and clip meter to fuse 10 tab (not the buss). clip other lead to batt + terminal. turn on the defroster and report the reading.
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked Last edited by funola; 05-20-2013 at 09:34 AM. |
#5
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note: key must be on, battery good and connected.
btw your DVM is the fuse! there's one inside. .
__________________
85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#6
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That's the problem. I'm guessing that I won't be able to successfully put the key in the on position.
__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes 1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod 2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die." |
#7
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I am not 100 percent sure on whether that key has to be on on not. try it w/o key - the battery negative has to be connected to chassis though. if the defrost switch light comes on then you will probably get a measurement.
__________________
85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#8
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I have a running '82 300SD -- I'll see if that defroster comes on when I hit the switch w/ no key.
__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes 1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod 2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die." |
#9
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don't bother the SD will definitely require the key. The method I described may bypass the key and supply power directly to the defroster. try it with a jumper instead of the DVM. If the defrost switch light comes on then you can use the DVM to take measurement.
__________________
85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#10
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If you remove the trim around the window, you should be able to find the wires that go to the heating elements. On my SD they are on the driver's side behind the c panel and are simple screw terminals.
Set your meter on the ohm range and measure the resistance across the two wires. Since its on a 16 Amp fuse all by it self, we can assume that its current draw is likely between 9-16 (117 watts to 208 watts) so we should expect to see a resistance value between 1.4 Ohms to 0.8125 Ohms or there abouts. Most meters (even this Fluke 77 at my desk here) are unfused at 10 amps and cannot sustain much beyond that for a long period of time so using a meter of that caliber, you might damage it. My $90 Triplett 9045, which is fused, is only fused to 10A.
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out. Check here for compatibility, diagnostics, and availability! (4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!) 82 300SD 145k 89 420SEL 210k 89 560SEL 118k 90 300SE 262k RIP 5/25/2010 90 560SEL 154k 91 300D 2.5 Turbo. 241k 93 190E 3.0 235k 93 300E 195k |
#11
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I just looked at the wiring diagram. fuse 10 is hot in run or start. the method I suggested should work by supplying power directly to the defogger relay/ measuring the current.
__________________
85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
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