mjz3348

I noticed a near constant clicking sound coming from the main fuse relay box in the engine when the engine is off.
The relay that is clicking (every few seconds) is the light grey HELLA 4RA 007 793-10
I don't know what this relay does, but I noticed that when it clicks once, my voltmeter shows a drop in battery voltage (engine is off).
As soon as the relay clicks again, the voltage starts to rise back up.

Can anyone explain what is going on? Is this normal? The car seems to run fine, but I never heard this before.
Thanks

pcy

I think it's an accessory relay. Disconnect all accessories, if any, including radar detector, cigarette lighter, etc. See if you see any difference after that.

peter2772000

Seeing as you didn't show where you're from in your sig, is it possible you're in a snow-belt state/province? If so, check all your grounds. You cannot believe what a bad ground will do to a DC circuit.

mjz3348

Houston, Texas
77 degrees here today.

mjz3348

Car is in in "off" mode - nothing running. Just this relay clicking on and off, drawing power when it does.

pcy

It is possible the relay is bad. If I were you, I'd get a new relay and install it and see if the symptoms change.

Diabolis

It could be something as simple and normal as the AC dryer fan cycling. Have you actually listened for it before? How rapidly does it click? Does it still click on and off after the car has been sitting for a few hours / overnight?

Arasimowicz

im having the same exact problem but my 20 it. When I pulled the clicked relay out and put it back in it stopped clicking and the car started up again. IM still researching it and ordering new relays.14 G550 died while driving

mjz3348

I found out that it was my accessory battery (in the rear by the hatch) was on its way out AND my main starter battery was not far behind. Once I replaced the accessory battery, the near constant clicking stopped.
What is happening is the main battery is used to keep the accessory battery charged. This is what enables you to lock/unlock the doors and operate other electronics while the car is off. It is vital that this battery be kept charged.
The clicking is when the accessory battery falls below a certain voltage and it switches on the main battery to top it off. The constant clicking was a warning to me (unknown at the time) that my accessory battery is no longer holding a charge.
And by association, it was putting undo stress on the main battery.

Not long after, I needed to replace my main battery as well. With both fairly new, the clicking only occurs when I open the car door and then only for a short time. Then it's gone. In addition, I got into the habit of putting my ML on a battery tender (Ctek-7002 AGM setting) when I am not planning on using the car for more than a day. This has worked wonders as it keeps both batteries at full charge when not in use.

Arasimowicz

I meant to say my 2014 G550. I also replaced both batteries a couple months ago but still have the clicking and car wont run. I will be replacing some relays and it appears the alternator is working

streborx

My '19 G550 gurgles, burps and farts all the time while parked in my garage. Found a guy on linkedin who claims to be an automobile exorcist. Still checking his references. Will follow up.