Originally Posted by chinny4290

Hey all.

So I've been driving my '74 450SEL and lately, I started to develop an electrical issue.

When cruising at town speeds (below 50MPH), sometimes, when letting off the throttle and letting the engine drop to idle speed, the gauge cluster would flicker out. It doesn't happen often, but only when there are short trips to the store or something. On the highway and at speed, it's fine.

Details:

- Tachometer would dance or die and so would Fuel/Temp/Oil pressure gauge, but speedometer remains unaffected and working
- There would be a relay click noise behind the gauge cluster every time it happens.
- It all happens like there's a lose connection or a bad ground.

- Drivability and engine performance seem unaffected

- When the gauge cluster flicks, I noticed the reverse lights also kicked in and out

- When it goes out, it goes out for a few second but all comes immediately back.


Steps to resolve:

I haven't checked the gauge cluster bulb for the battery yet (it could be out and not telling me that there's a charging system problem).

But some preliminary research suggests either voltage regulator (on the alternator or on the body) or the need for a new alternator...

I'm also thinking a relay could be going.

Any suggestions? I plan to replace both voltage regulators and just getting a new alternator since they're pretty cheap and easy to replace.