1985 300SD
Problem with turn signals. No electrical work done since battery change last yr until this wk.

For 2 months, turn signals sometimes normal. Sometimes flash intermittently. Sometimes do not come on. Sometimes buzz like a bee instead of just blinking. When signals buzz, the turn signal light on IP flickers as fast as buzzing.

1 week, turn signals would mostly not come on at all. Sometimes turning the hazard flasher on and off dozens of times would return turn signals to normal. Sometimes not. Looked at turn signal exterior bulbs, all 4 turn on [after jumpering 30 to 49a as below].

Cleaned the hazard flasher according to the peach parts wiki.

Turn signals worse. Worked normally one time then totally off. Hazard flasher worked once now not working at all.

Saw post about jumping connector to hazard flasher. Jumping 30 to 49 did nothing that I could see.
Jumped 30 to 49a and turn signals would come on and not blink if signal lever pushed to left or right turn signal position. Now drive car with signalling by moving turn signal lever on and off.

Replaced fuse #12 with a spare and sandpapered the fuse ends and terminals for #12 on the fuse compartment. No change. Radio always works normally whenever turned on; radio is fuse #12. Not aware if any other fuse is involved in turn signals or hazard flasher.

What other tests to tell if hazard flasher, relay or turn signal combo switch or something else is defective. Thanks.

I believe there is a good chance that you need a new hazard light switch. Cleaning the switch does not always fix the problem. Get a genuine Hella switch maybe from a wrecked car.

Jumped socket from 30 to 49a with wire. Turn signals turn on without flashing when turn signal lever moved.
Reassembled hazard flasher today and reinstalled. No hazard flasher function. No turn signal function.

1 flasher base with plug
2 flasher shuttle
3 flasher plug on car. jumpered 30 to 49a. Turn signals turn on without flashing when turn signal lever moved.

What to test next?

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me thinks it's time to pull the ashtray and remove the flasher module, and replace it...

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Yes, it was the flasher.
Replaced it.

Brief procedure.
Make 2 tools out of coat hangers. Picture 1
Disconnect battery .
Pull out instrument cluster using tools. See picture2 . No screws or bolts or clips secure the instrument cluster. Picture 2
Pull out some instrument cluster wires to get enough room to reach flasher relay and socket. Picture 3

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Pull old flasher relay out. Picture left below
Pull socket for flasher relay up and out. Pictures middle, right below. Was not able to install flasher relay without pulling socket out.

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Plug in new flasher relay. Where plug for relay sits. Picture left below
Put flasher relay and socket back in place. Picture middle below.
Put instrument cluster back. Make sure all wires are reconnected.
Reconnect battery.

Was able to use a voltmeter and circuit diagram to confirm that the hazard flasher switch was good. For novices like me, it means a voltmeter can measure continuity between the correct pins on the hazard flasher switch when the switch is on or off. The diagram shows in line drawing which terminals should connect when on or off. Picture right below.

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So, I have the turn signals working fine, but I notice they start to buzz and change their blinking pattern, like they are slowing down...

I looked up the flasher relay on peachparts for my 83 300SD and the pictures all show a flasher unit with 4 metal prongs instead of three like the one you took out. Did your new one look the same as the old one I assume?

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