1979 300D chattering starter when hot

[Nate Stanley]

We’re having problems on our ‘79 300D with the starter cutting out intermittently, usually when the engine is warm. When the engine is cold, there is usually no problem firing the engine.

When warm, you can feel the starter kick in and out while the engine cranks, and it’s murder on the bendix drive, not to mention the ring gear.

What we’ve done:

1: New Battery
2: New starter, noticed the Bendix drive gear was really loose on the old starter shaft, probably as a result of the chatter problem.
3: checked & cleaned ground straps from battery to body, and body to transmission.


When the car is hot, the best way to get the starter to crank is to jiggle the keyswitch while turning the key, but that also doesn’t guarantee a hot start. Sometimes moving the turn signal stalk during cranking helps to complete the circuit.

I have a new keyswitch ready to install, but I have a sneaking suspicion that there’s more to this, since I also hear a clicking noise behind the dash while the starter circuit is energized.

What makes this more difficult is that there is no way to jump start the car like there is with on my '84, which has a terminal block on the passenger side fenderwell, the '79 does not have that feature.


Has anyone had this problem?

Is there another relay I should check that lives behind the instrument cluster?

Is there another ground strap under the dash that needs checking?

The Haynes manual mentions for the 123.130 body an A/C / Starter relay, but I don’t know what its function is—(item 38 on the wiring diagram)

Thanks in advance for any help, I just want this car to be running right this weekend.

Thanks to All,