Vacuum/hissing sound fron dash (headlight switch)?

[Cadence]

1994 E500

I have what sounds like a vacuum leak/hissing sound coming from the far left side of the dash.

The noise is coming from the headlight switch area and if I change the headlight adjustment roller from 0 to 3 the sound is reduced!

This noise is only present at idle (barely) and during deceleration, i.e. during vacuum. At cruise speed and acceleration the noise goes away.

What on earth could cause this noise? Are there vacuum hoses that go to the dash for the headlight aiming control?


This is the switch in question:

 

[Jelmer]

The light level is indeed controlled by a vacuum, iirc two vacuum tubes are connected to that headlight level switch.

That part is easy enough to open up, just pull off the light on/off switch, take out the bolt that you find behind that and you can pull it towards you. Hmm, might be that I forget about the parking brake, but that's also a matter of one screw right behind the "P".

Either a tube has broken/come off or that switch is broken. Either way, easy and cheap fix.

 

[Cavanman]

Here's a picture of what's behind the switch panel. The fitting with the three purple pipes is what fits onto the back of the headlamp adjuster switch.

I think you may have to dismantle the dash this far to be able to check these pipes for certain. It's not too bad to get it this far, though you do have to prise some of the fittings which can be a bit nerve racking.

You also get better at dismantling if you have to repeat it because you forgot to re-attach the headlight adjuster pipes when putting it all back together...

 

[Cadence]

Here's a picture of what's behind the switch panel. The fitting with the three purple pipes is what fits onto the back of the headlamp adjuster switch.

I think you may have to dismantle the dash this far to be able to check these pipes for certain. It's not too bad to get it this far, though you do have to prise some of the fittings which can be a bit nerve racking.

You also get better at dismantling if you have to repeat it because you forgot to re-attach the headlight adjuster pipes when putting it all back together...

Thanks for the photo. I removed the headlight switch surround panel and saw those three purple vacuum lines. Everything looks fine but there is certainly a sucking/hissing noise from the switch.

Maybe this noise is normal, although it doesn't seem very Mercedes Benzish??!?!?! I guess the next step is to order a new $witch.

 

[Cadence]

Thread revival!

I asked this question about my ex-'94 E500 but the ROW-spec 1993 500E I just purchased has the headlight height switch and makes EXACTLY the same air hissing sound.

It really bothers me (yes I am OCD about noises) but since both cars make the same noise I have to believe it is normal. Has anyone else noticed this noise?

 

[gsxr]

There should be zero noise. If the plumbing & fittings are all intact, I suppose it could be a faulty switch. The dial should be silent even when changing position.

 

[Klink]

There can be excessive noises in those adjustment switches if there is continuous flow through them such as occurs when there is a leak on the operating side of the circuit. One of your lines going out to the lamps may have a leak and/or be disconnected, and/or one or both of the vacuum operated elements inside the lamps is/are leaking. They are available separately as replacement parts if that proves to be the case. There are also some short connecting hoses inside the lamps that may be leaking. Faulty switches are common enough as well. If you have no leaks on your operating side then it is likely the switch itself.

 

[2phast]

It is common for these switches to leak. If your vacuum lines are ok and the rubber fittings are ok, the problem lies with the switch. I have seen many of these leak.