Bizzare Happening

[reflexboy]

Hi all, I have a 96 C280 straight six. Whenever the heater fan switch is either in the 'on' position or set at any fan speed number I can hear a slight ticking noise and can feel a slight tap from the brake pedal. If I put the fan switch to zero, it goes. Any ideas guys?

 

[reflexboy]

also, a rubber pipe under the bonnet seems to move correspondingly with the noise/tap?

 

[landover]

also, a rubber pipe under the bonnet seems to move correspondingly with the noise/tap?

Sounds like a bearing away in the heater motor.

 

[markyce]

Hi Guys,
I had this on my W202.........IT'S A STICKY DUO VALVE !
Thats the 2 little heater/cooling autovalves in the fuse box area that control temp to both sides of the cabin. Best way to check is to turn heat full on and see if the ticking happens, then turn to full cold........when I did this the ticking was present on hot and not when on full cold.

Arnie gave me this a while ago....thanks again Arnie :lol:

 

[landover]

Hi Guys,
I had this on my W202.........IT'S A STICKY DUO VALVE !
Thats the 2 little heater/cooling autovalves in the fuse box area that control temp to both sides of the cabin. Best way to check is to turn heat full on and see if the ticking happens, then turn to full cold........when I did this the ticking was present on hot and not when on full cold.

Arnie gave me this a while ago....thanks again Arnie :lol:

Good to know .Thanks.

 

[reflexboy]

FAO 'Markyce'

Thanks for your reply Markyce. I must admit that I bought the car in the summer and didnt even have the heater on, just the air con during the warmer weather, so this may well tie in with what your saying about it only happened on hot for you not cold. I shall try this next time i go out in the car. The heater and the a/c all seem to work fine nonetheless. Do you know if Im able to free the sticking valve or do you think it may need replacing, if so any idea of cost? When you say the fusebox area, I take it you mean the passenger side, as I've got some fuses/relays there under a large plastic cover, but Ive also got some fuses on the drivers side also,both under the bonnet.Any futher clues to what these duo valves look like and their location. Many thanks mate.

 

[OlafMaxwell]

Sudden changes from full hot to full cold generates a lot of thermalk movement in the heater ducts, this makes a lot of noise too and is harmless.

 

[joe bloggs]

The duo valve is supposed to click, its what regulates the temp, it is either open or closed depending on supply to its terminals (supply = cold, no supply = hot) this was done so that if the supply failed you would always have heat. The clicking is just the valve doing its job.

 

[reflexboy]

Thanks for your comments guys. Whilst I appreciate that a solenoid valve will make a clicking sound when it either opens or shuts, it makes a ticking noise and a vibration through the brake pedal at the rate of approx one per second! I take it this is not normal?

 

[landover]

It sounds like the heater fan is loose and hiting off the caseing.

 

[200e]

Just bought a 94 c class I had the same problem it sounded like a relay clicking I took it to an independent mb dealer he checked it out and it is the heater duo valve that need replacing he disconnected the wires from it and the clicking went away so I have ordered one from euro 75 quid should get it on Friday

 

[joe bloggs]

Noooo, OK, the valve is supposed to click open/closed to maintain the interior temp, sensors in the car tell the ecu how hot/cold it is, the ecu will open/close/pulse the valve whatever way it thinks will allow enough hot water through to the heater to maintain the set temp. the click/vibration is the valve opening and the electric circulating pump kicking in to run the water through the heater. Of course it will go away if you unplug the valve, its not going to work with no power is it. Remember this valve can only open or close so therefore the only way to regulate the temp is to have the valve opening / closing continually, if on fully hot or cold the clicking should stop, but while in the centre 22 setting the valve can rattle on and off. you can try moving the valve away from other components to minimise the sound, but if the heater is otherwise working ok the valve is ok. (trust me I've seen thousands)

 

[numbnuts]

Noooo, OK, the valve is supposed to click open/closed to maintain the interior temp, sensors in the car tell the ecu how hot/cold it is, the ecu will open/close/pulse the valve whatever way it thinks will allow enough hot water through to the heater to maintain the set temp. the click/vibration is the valve opening and the electric circulating pump kicking in to run the water through the heater. Of course it will go away if you unplug the valve, its not going to work with no power is it. Remember this valve can only open or close so therefore the only way to regulate the temp is to have the valve opening / closing continually, if on fully hot or cold the clicking should stop, but while in the centre 22 setting the valve can rattle on and off. you can try moving the valve away from other components to minimise the sound, but if the heater is otherwise working ok the valve is ok. (trust me I've seen thousands)

The valve is not near other components and is bolted to the inner wing at the bulk head it should not make a ticking noise all the time it should only click between hot and cold settings reflexboy was asking what the problem could be 200e had the same problem and was told it was the duo valve.

 

[200e]

Just an update got duo valve fitted today car is perfect now the cost for fitting 30 quid including a coolant flush and new antifreeze just got an alarm to get fitted now.

 

[joe bloggs]

Sorry to dissagree, but if it only "ticked" between hot and cold then on its hot tick the water would be running through the heater continually, and when ticking on cold there would be no water. To maintain a 'warm' interior, i.e set at 22, the valve must continually tick on and off to regulate coolant flow through the heater.

 

[joe bloggs]

Good to hear the new valve is quieter, but it will still click on and off regularly, you will feel it if you grip the valve when the car is warm and the heater on a middle setting, it will pulse on and off regularly.

 

[reflexboy]

Oh dear, it seems like I have caused a bit of a stir! All these disagreements at a time of festive happenings and goodwill? My heater works fine, so does my air con. The clicking (approx 1 per second) only happens when the temp is set anywhere between halfway and full heat, but never when on cold or with the a/c on cold. I can actually feel the water/coolant gushing through the duo valve and related rubber pipework consistantly with the ticking. As I said before the slight ticking noise is also noticeable feeling it through the brake pedal when pressed. I think I need to contact my mate of a mate of a mate of a mate's sisters brother's uncle's third removed lesbian ethnic collegue! whom is an MB specialist, with 20yrs experience as an MB technician. Keep your comments coming fellas. Thanks again, you have all been very helpful. :lol: :lol: :lol: :lol: