Relay "clicking" periodically when ignition is off

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xiaohao76

New Member
Hello guys,

I'm facing a weird issue with my Kia Cerato.

I purchased this car a few months back from the secondhand market. While resting in my car with the ignition off, I noticed there's a knocking sound coming from the back off my car periodically. Initially, I ignored the sound and didn't think much about it. It was until I faced a problem where I was unable to start the car when the car was not driven for ~3 days, as the battery level was low and needed a jumpstart.

I started looking deeper into what could be draining the car battery within a few days (the battery is new). Unplugging the car cam did not help and I had to jumpstart the car on a second occasion.

Then I remember the knocking sound which I was hearing periodically with the engine off and suspected that could be the cause of battery drain. The knocking sound could be heard every 13 seconds. Guessing the sound was coming from the fuel pump, I opened up the fuse box. And true enough, the fuel pump relay could be heard clicking every 13 seconds. I unplugged the fuel pump relay, and the knocking stopped.

With the fuel pump relay unplugged, now I could hear another sound coming from around the engine (again every 13 seconds). So this time, I unplugged the main relay and the sound stopped.

So it seems like every 13 seconds, there is something powering up the main relay, which is also powering up the fuel pump relay and a few other components and it's draining the battery.

Would anyone be able to advise what could be the problem? Is this normal?
 
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My initial guess would be a corroded connectors somewhere with leakage between the pins.
Or, that a module on one of the data bus circuits is not shutting down properly - which could have the same cause, or it could be a faulty module.

Check all the fuses are OK to start with.

One test method for modules not shutting down is to use a multimeter on the millivolts range and measure across the testpoints in the top of each fuse. It will be non zero on any fuses that are passing current - then look what that fuse relates to in the fuse chart.

Do that with the two relays out, so you are not reading the current they take.


Also check for any sign of water ingress anywhere, under the carpets or below the boot lining. If there is any trace it has been damp, look for any connectors that may have been affected in those areas - clean and dry them thoroughly, then treat the contacts with deoxit and the outside with WD40.
 
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Usually, not always, there is a mode vehicle can be put in to dump codes
via dash indicators. Sometimes involving using a jumper in a fuse block
or scan block connector. Google you vehicle model and "codes" to see if you
can get a hit, or go to that manufacturers forums to see if anyone else
has discussed code dumps.
 
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aliarifat794 said:
It can be due to a short circuit or a faulty relay itself.
Click to expand...
I've replaced the main relay, but the issue still persist. And I don't think there is any issue with the fuel pump relay, else it wouldn't be clicking.

I troubleshoot today by pulling the fuse out one by one. I noticed the following:
- Pulling out ECU 1 fuse, both main and fuel pump relay stopped. and when it was plugged back in, no further clicking was heard. But issue will re-surface once the ignition is turned on and off again.
- Pulling out SNSR 2 fuse, the fuel pump relay stopped clicking. I checked the owner's manual, SNSR 2 fuse is for the following: Oil Control Valve (#1, #2), Camshaft Position Sensor (Intake, Exhaust), F/PUMP Relay,C/FAN LO Relay, Immobilizer Module
- Pulling out the fuel pump fuse, it was surprising to me that the fuel pump relay did not stop clicking.
 
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I bought a multimeter to test today, with my very limited knowledge haha.

What I noticed was that, many fuses have a reading of 12+ volts. I suppose this is because there is still power from the battery to the fuses?

There are some fuses that are ~0.5 volt. And when the relay clicked, it increased to ~1 volt then drop back to 0.5 volt.
I'm not sure what I should be looking out for

I also checked for water traces, but there doesn't seem to be any.

I troubleshoot further by pulling the fuse out one by one. I noticed the following:
- Pulling out ECU 1 fuse, both main and fuel pump relay stopped. and when it was plugged back in, no further clicking was heard. But issue will re-surface once the ignition is turned on and off again.
- Pulling out SNSR 2 fuse, the fuel pump relay stopped clicking.
- Pulling out the fuel pump fuse, it was surprising to me that the fuel pump relay did not stop clicking.

Does my above observation tells us anything? I checked the owner's manual and the SNSR 2 fuse if for the following: Oil Control Valve (#1, #2), Camshaft Position Sensor (Intake, Exhaust), F/PUMP Relay,C/FAN LO Relay, Immobilizer Module
 
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If you are reading 0.5 - 1V on fuses that should be unpowered, the problem could be a loose or corroded body / chassis ground connection somewhere.

Look for any wires to bolts on the bodywork, that could be corroded - or have not had the point removed when being assembled. Check they are tight or clean them and re-assemble.
 
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xiaohao76 said:
Pulling out the fuel pump fuse, it was surprising to me that the fuel pump relay did not stop clicking.
Click to expand...
xiaohao76 said:
What I noticed was that, many fuses have a reading of 12+ volts. I suppose this is because there is still power from the battery to the fuses?
Click to expand...

The feed to something like the fuel pump will go through the fuse and the relay, but that can be in either order. If the power goes to the fuse first, the fuse will be powered all the time.

If you measure the voltages on the relay contacts, that will be 12 Volts when the fuse is in place and will drop when the fuse is removed.

The relays are there because some control module is not capable of supplying enough current to power the load, so a relay is used. The fuse only supplies the relay contacts and the load. The relay coil is powered by the control module, so you still hear the click when the fuse is removed.

Some relays are have one side of the coil connected to ground, and the module turns the 12 V on and off. Other relays have one side of the coil connected to to 12 V and the module turns the negative to the relay on and off.
 
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Some good info here! Definitely clean all the battery power and ground connections. I still strongly suggest getting the vehicle scanned. You could be looking for the proverbial needle in a haystack.
 
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