Clicking behind driver seat - sounds like someone is doing morse code

[Kozuchowski]

I have exactly the same symptoms he described(03 raw nsx). I might add that this does not happen when the engine is cold, but when it is warm. Three colleagues give different solutions: ground cable, alternator, ignition switch.I think this is not a coincidence and it would be worth finding out and talking about removing the fault like Technical Bulletin. Our cars are getting old. This will be helpful to others.

 

[ralph cerbone]

could have been AC ripple (as in ac current ) coming from alternator ,Old Guy what do you think .

 

[drew]

The Main Relays are in different locations for the models in this thread.

Need better descriptions of the offending module.

 

[Kozuchowski]

to Drew. This is about the fuel pump resistor relay

 

[Old Guy]

could have been AC ripple (as in ac current ) coming from alternator ,Old Guy what do you think .

I am thinking no.

If the primary electrical connections (includes the battery connections and the connections through the ignition switch) are in good condition the battery acts as a pretty good filter to eliminate the AC ripple associated with normal operation of the alternator. Even with a dead alternator diode I would expect that all you would see with a scope is a brief drop from 14.5 volts to the battery voltage during the short time when the dead diode would normally be conducting. If the alternator (or something else) is generating high frequency / short duration voltage transients the battery will not eliminate those; however, that would typically not manifest itself as a clicking in a relay.

Relays have pick-up and drop-out voltages. A typical nominal 12 volt through hole Panasonic automotive grade relay will operate with an applied voltage in the 5.5 - 7 volt range (pick up voltage). However, once the relay contacts have closed they will remain closed until the voltage drops down to about 2 -3.5 volts.



So, in order for the relay to chatter because it is dropping out because of voltage fluctuations the voltage must be dropping down to around 3 ish volts. If the vehicle 12 volt system voltage is dropping down to the 3 volt range then that should be very obvious (other things would be happening).

If the relay is chattering I expect that it is either because of an intermittent (bad) connection that is causing the relay to chatter or something is actually turning the relay on and off. Those bad connections could include the battery and ignition switch; but, I would expect those to cause additional problems on other stuff which should be evident. A bad electrical connection right at the relay socket or on the relay circuit would limit the problem to the relay. If something is turning the relay on and off that would be a separate mystery.

 

[Kozuchowski]

Old Guy, I determined by monitoring the output from the ECU. As you wrote earlier, it is a transistor that closes the relay circuit to ground. And I thought that the fault was on the ECU side (I started looking for new ones). But I found this Thread on Prime and was surprised by the solution to the same problem.

 

[eug888]

Hi, had the exact same issue, we were able to fix the clicking relay by repairing the alternator, the diodes were busted thus the voltage the battery drops to around 12v, which is the reason for the intermittent clicking. Glad to have figured out the cause. Hope this helps!

 

[Kozuchowski]

It will definitely help.
Thank you for posting on the forum. This is another case of a clicking relay solved by replacing the Rectifier in the alternator. Will go in this direction. Thank you again

 

[Old Guy]

Something smells of fish. When the engine is out of the VTEC operation zone the fuel pump relay should not be energized so it should not be clicking, even if your vehicle 12 volt system is going screwy. If the relay is clicking when the engine is outside the VTEC operating range you have something else happening.

 

[Kozuchowski]

I know it's hard for you engineers to explain this situation. But it does happen, and in my case it occurred on a hot summer day after a long drive. While putting the car into the garage, I heard a clicking noise. and since I am an electronics technician, I checked the wiring and I am sure that the fault comes from the ECU. I don't know what is the cause: temperature, voltage, level, shape? I think the transistor inside the ECU is failing. its connector is failing due to temperature or voltage, or the base receives a command from the Controller, which I doubt. I have driven 500 km since the fault occurred and nothing. I bought a second ECU and if it occurs, I will replace it. Narrowing down the search. While searching this forum, I came across similar cases that were solved by replacing the ground cable or IG switch, i.e. the voltage level. There are cases when the rectifier in the alternator failed, i.e. the voltage line and level.