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Bad ignition switch?

studmuffed

Member
Joined
Nov 16, 2017
Location
Va
Hey all,

I'm working on putting a new stereo in my 240 and I am not getting 12v switched power in any position. The ignition switch starts the car just fine but is there any way that it could be failing to send a signal to the stereo?

I have checked all of the black connectors and they seem to work just fine and I am having trouble finding a full wiring diagram.

Nick
 
I checked fuses 1 and 8, both are good. Is an in line fuse standard? I didn?t see one but can do some deeper digging. Wiring seems to be stock.
 
If you have a wiring greenbook for your year, or something close, look on roughly page 8 and see if they show the radio connector. If so, measure across ground and the 2 power pins - one should be on all the time, the other should be switched.

It's fairly common for radio installers to futz with the wiring, so you may need to trace the switched +12 wire from the connector to the fuse block (it's probably OK from fuse block to ignition switch).
 
On the factory stereos I've pulled out the red power wire had a white connector on it that has the fuse built into it, pop it open and a regular glass fuse comes out. Have you checked if power is getting to the ignition switch and then coming out the ignition switch?
 
If you have a wiring greenbook for your year, or something close, look on roughly page 8 and see if they show the radio connector. If so, measure across ground and the 2 power pins - one should be on all the time, the other should be switched.

It's fairly common for radio installers to futz with the wiring, so you may need to trace the switched +12 wire from the connector to the fuse block (it's probably OK from fuse block to ignition switch).

I don't have a greenbook but I have done this a few times so I know which one it should be. The green -> yellow wire is getting 12v constantly. the Yellow/Black -> red wire is never getting any voltage. I just spent a good 30 minutes tracing the yellow/black wire back. It gets confusing when it joins up with another harness near the clutch pedal and splits off in a few directions.

Additionally, fuse #1 isnt getting voltage when switch is off but is getting voltage when switch is on, as expected.
 
On the factory stereos I've pulled out the red power wire had a white connector on it that has the fuse built into it, pop it open and a regular glass fuse comes out. Have you checked if power is getting to the ignition switch and then coming out the ignition switch?

No, I havent checked ignition switch power yet. Do you know if a faulty ignition switch would cause any other issues? My cigarette lighter is still working I think (need to put everything back together to confirm.

Edit: after doing some digging it seems like there isn't anything in between the fuse box and the radio for a 1993 240. This means that the wire should be shorting or broken somewhere. I'll keep digging for a little while but I am getting close to just splicing in a new wire.
 
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I'm replacing my ignition switch because some of the contacts are loose so sometimes my horn, windshield wiper, rear defrost, blower and a few other things dont work just cause they aren't getting power. Gotta hit the switch on the back underneath the dash sometimes and everything works, don't have a radio in the car yet so don't know if that's affected.
 
I'm replacing my ignition switch because some of the contacts are loose so sometimes my horn, windshield wiper, rear defrost, blower and a few other things dont work just cause they aren't getting power. Gotta hit the switch on the back underneath the dash sometimes and everything works, don't have a radio in the car yet so don't know if that's affected.

Now that you mention that, my wipers did stop working for a little while when the key was in the "ON" position, but they did work while in "ACC" position. That to me points towards ignition switch, right?
 
Yeah, try to jiggle the switch to see if you get power, hook up a test light or multimeter and then also try taking it off and cleaning it if needed
 
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