Relay clicking under dash on lite acceleration and when holding the pedal

[Mailbox14]

Hello again,

I am posting for a friend. Under light acceleration, I hear a relay clicking under the dash. If i let off the gas it doesn't click anymore and when going fast (50-60 km) i don't notice it as well. if i hold the accelerator pedal i hear it the clicking as well.

Any ideas which relay this is?

2004 Audi A4 B6 - 185k.

[Mailbox14]

Hello again,

I am posting for a friend. Under light acceleration, I hear a relay clicking under the dash. If i let off the gas it doesn't click anymore and when going fast (50-60 km) i don't notice it as well. if i hold the accelerator pedal i hear it the clicking as well.

Any ideas which relay this is?


2004 Audi A4 B6 - 185k.

Any ideas what to change would be appreciated all!! Sorry for the troubles again.

[old guy]

Automatic or manual transmission?

[Mailbox14]

Automatic or manual transmission?

Automatic old_guy.

[old guy]

The conditions in which you describe the increased relay activity is when the intake manifold is either neutral or under slight positive pressure. With an automatic transmission there is an auxiliary vacuum assist pump that is used to keep a vacuum supply to the brake booster. There is a vacuum sensor beside the booster that controls the vacuum assist pump. If there isn't adequate vacuum the pump will cycle on.

I suspect you have a small vacuum leak somewhere in the brake booster vacuum assist circuit and consequently the vacuum assist pump is cycling to maintain adequate vacuum.

With the car at idle you can wiggle the hoses connecting to the booster and outward and see if you hear any hissing sounds. Check around the SJP as well as the hoses coming from the vacuum pump. I suspect you will find something. Another possibility is a faulty check valve in the same area. If the check valve allows any boost pressure into the brake vacuum circuit it will most definitely cause the vacuum pump to run a lot.

You should be able to force the pump to run by pulling back on the vacuum hose connection where it goes through the plenum wall to reduce the vacuum to the brake booster vacuum sensor. Do this at idle and have someone inside the car listen to see if it creates the relay noise that you are hearing while driving.

[charlie2981]

Not to hijack this thread, but I am having the same exact problem. I found the clicking to be the brake booster relay under the dash, so my suggestion would be to check that one out. In my current situation, I also found the small 15 amp fuse (#9) to be blown that it is tied into. I ordered a new relay thinking the relay was bad, put it in, as well as a new 15 amp fuse. The second I hit the gas pedal at idle, the fuse immediately blows, and the relay begins its song of clicking once again. Checked for vacuum leaks at idle by wiggling, as well as spraying soapy water, and nothing. New revised SJP is only a few thousand miles old, and has no hissing coming from it, and I verified it is still good. The only hissing I was able to hear at all was once I turned the car off. I could hear hissing from what appears to be behind the brake booster. Soo frustrating trying to figure this out.

[charlie2981]

In looking over other threads, it appears that it may be a vacuum problem with the scenario we have, so I am in the process of ordering/replacing all the check valves under the hood since I never did that since ownership of the car. I'm not going to attempt to put another fuse in until I do this, but will report back with results for you!

[Let it snow]

Not to hijack this thread, but I am having the same exact problem. I found the clicking to be the brake booster relay under the dash, so my suggestion would be to check that one out. In my current situation, I also found the small 15 amp fuse (#9) to be blown that it is tied into. I ordered a new relay thinking the relay was bad, put it in, as well as a new 15 amp fuse. The second I hit the gas pedal at idle, the fuse immediately blows, and the relay begins its song of clicking once again. Checked for vacuum leaks at idle by wiggling, as well as spraying soapy water, and nothing. New revised SJP is only a few thousand miles old, and has no hissing coming from it, and I verified it is still good. The only hissing I was able to hear at all was once I turned the car off. I could hear hissing from what appears to be behind the brake booster. Soo frustrating trying to figure this out.

I am assuming you have an automatic transmission. Fuse #9 keeps blowing because you have a bad brake vacuum pump or the wires to the pump are faulty.

[charlie2981]

I am assuming you have an automatic transmission. Fuse #9 keeps blowing because you have a bad brake vacuum pump or the wires to the pump are faulty.

Yeah I think you are right with it being the brake vacuum pump, as I just checked the wiring. Now the fun part of finding a used one for cheap!

[Mailbox14]

Thanks everyone. I will post back as to what is discovered. Old guy, I will check out what you mentioned and Charlie, thanks for the added info.....

Also, Happy New year to all!!

[CFella]

I'm not going to attempt to put another fuse in until I do this, but will report back with results for you!

I love when they never report back.....

[pablolizarraga]

For weeks I had same symptoms (relay clicking) along w/ codes indicating malfunctioning vacuum pump. However, it wasnt until i had misfires across the board, loss if braking, and hearing the brake vacuum pump go into overload that I discovered the source. (Fortunately all this happened while I was parked).
Popped the hood and with the engine running I tracked down the hissing. Pretty hard to miss...


IMG_7757.JPG

I touched the hose and it just disconnnected. I think it was the vacuum that was keeping it attached.


Sent from my iPhone using Audizine

[CFella]

For weeks I had same symptoms (relay clicking) along w/ codes indicating malfunctioning vacuum pump. However, it wasnt until i had misfires across the board, loss if braking, and hearing the brake vacuum pump go into overload that I discovered the source. (Fortunately all this happened while I was parked).
Popped the hood and with the engine running I tracked down the hissing. Pretty hard to miss...


IMG_7757.JPG

I touched the hose and it just disconnnected. I think it was the vacuum that was keeping it attached.


Sent from my iPhone using Audizine

I will look for this hose when I go home. I do not have any codes stored though. Wish I did actually as it would give me a place to start

[old guy]

A small vacuum leak in the brake booster circuit isn't going to give you any DTC's as long as the vacuum pump can make up the difference.

[CFella]

Well just drove home from work...20min ride...didn’t click once.

[raayed]

Hello again,

I am posting for a friend. Under light acceleration, I hear a relay clicking under the dash. If i let off the gas it doesn't click anymore and when going fast (50-60 km) i don't notice it as well. if i hold the accelerator pedal i hear it the clicking as well.

Any ideas which relay this is?

2004 Audi A4 B6 - 185k.

hi have the same issue here
i wonder did you find the problem
plz let me know as i dont know how to deal with it
thanks
raayed

[raayed]

hi have the same issue here
i wonder did you find the problem
plz let me know as i dont know how to deal with it
thanks
raayed

A4 2003 4 cylinders 2.0 none turbo