Locating parasitic drain, ~80mA parasitic drain from CDS fuse, what is this fuse?

[Aircheese]

Hi,

I am trying to solve my is250 2006's Battery draining issues for a few months.

The drain comes first at around 0.15A. After I located my insurancer's black box and disconnected. (the box has been deactivated). The drains now comes to ~0.1A, where the thing becomes awkward. Battery changed, i can just live with it but it's still something there. I checked every fuses by measuring the voltage drop inside the cabinet, everything was calm beside the keyless ignition, which is expected.  

I even built a device to measure the voltage across many hours. (The little spikes are cause by the device itself. The device was supplided with its own power source)

Data recording started at around 11pm after the engine off for 4 hours. Lower voltage means higher current. In the second graph, the curve is probably because of the temperature changing overnight. An interesting finding is that the car will finally go rest after ~10mins (0.15 hours).

 

Today, I finally decided to check the drain again. I was quite worry that the drain casued by the alternator which changing it will be a huge work for me.

After some investigation, the source of parasitic draining finally came to the CDS fuse located in the engine bay.

Close the door for ~3 mins, 0.33A. Most of the current is from MPX-B. This current draining is ok.

 

When the computer was down (After 10 mins). With CDS fuse on, the current is ~ 0.1A. Before pulling out the fuse, I also measured the voltage drop on the CDS fuse (0.4mV), it comfirmed that the current through this fuse was around 50~60mA according to https://www.powerprobetek.com/wp-content/uploads/2018/12/fuse-charts.pdf

 

When I pulled out the CDS fuse. The current droped to ~20mA. Which is the ideal drains for a normal car (<35mA).

 

Unfortunately, I cannot find a good infomation about the CDS fuse, and I have no idea which system is relying on it so I didnt start the car with the fused unplugged.

It is really frustrating, that my maintanance manual may be for Amarican version which dose NOT have the correct fuse diagram/description with CDS.

 

Does anyone know what is this CDS fuse for?

[johnatg]

Well done building the voltage tracker!

A bit of google search shows the CDS fuse refers to the Aircon Condenser fan. You probably don't need it, at least in the winter.

[Aircheese]

1 hour ago, johnatg said:

Well done building the voltage tracker!

A bit of google search shows the CDS fuse refers to the Aircon Condenser fan. You probably don't need it, at least in the winter.

Thanks for the info, I just found the CDS in the manual in another separated pdf document. But still i couldnt locat it in eletrical diagram.

It is indeed related to a fan but i am quite confused between condenser fans vs radiator fans. Looks like the CDS supply the current.

Edited January 11, 2021 by Aircheese
Add relay logic table

[Herbie]

Excellent diagnostic and fault-finding skills Martin, well done.

I don't suppose you fancy sharing the details of your voltage logger with us do you?

[johnatg]

I think that the aircon condenser fan will run all the time with the aircon on. The rad fan won't run with the engine cold. So you should be able to identify which is which

Of course the fan might have failed with a slight short. 

[Herbie]

I'd check all three relays for operation, coil resistance and contact surfaces.

[Aircheese]

12 minutes ago, Herbie said:

Excellent diagnostic and fault-finding skills Martin, well done.

I don't suppose you fancy sharing the details of your voltage logger with us do you?

Thanks, to build the device requires some basic electronic knowledge and some basic programming skills. I am using one of the STM32's development board to record the data.

The measurement circuit is a basic voltage divider consists of 2 resistors, scaling down the Battery voltage ~14V to microcontroller's voltage 3.3V or 5V. Then program the microcontroller to measure the voltage by its ADC (analog-digital converter). Then the data is recorded to micro SD card. I sample the voltage 10 times every second for 2 days (the Battery for the recorder only last that long.)

It might sound complicated, but it is really simple once you learn some tutorials.

I would recommend starting with Arduino, it has all the required functions, ADC and SD card, and it is really easy to use if you want to build one.

 

 

[Herbie]

Brilliant Martin, thanks.

[Aircheese]

13 minutes ago, johnatg said:

I think that the aircon condenser fan will run all the time with the aircon on. The rad fan won't run with the engine cold. So you should be able to identify which is which

Of course the fan might have failed with a slight short. 

 

4 minutes ago, Herbie said:

I'd check all three relays for both operation and contact surfaces.

Thank you both,

I will check them next time. The weather doesnt looks good here in the next few days. 😆

[Aircheese]

Just pull out the Fan Relay No. 3. However, the current is still on CDS fuse. The relay was tested fine.

The CDS is surely not connected the the relay directly .

Also, the diagram marked on the fuse box is different from what I see in the manual I have (Fan Relay No3 is the same).

I will live with that ~0.1A drain now untill i can find more info rekated to the CDS fuse.

Next time I will test the current on CDS when AC on to see if it does supply the power to the fans.

[is200 Newbie]

I have never considered these cars with an insurance black box in them - they need to be really confident in fitting them to these cars due to the amount of electronics in them. Just as a question ... did the install of it bring down your insurance significantly. My lad had one on his fist car years ago and it kept his policy low, mind you it was only a Ford KA but a little pocket rust rocket 😀

[Linas.P]

My first insurance with Bell had 3 months black-box. At the time I was 25 and it took insurance premium from £2800, to ~£2200.

But after that (very first insurance) there are no difference whenever it is with black-box or not. So yes, for younger driver and for first insurance it could reduce premium, but not as much as they advertise.

As well my blackbox was just plugged into cigarette lighter / 12V socket and it is only powered when engine is on or ignition is on. So I expected no parasitic drain from it - I would have never agreed to hardwired box.

[Aircheese]

On 1/15/2021 at 2:19 PM, is200 Newbie said:

I have never considered these cars with an insurance black box in them - they need to be really confident in fitting them to these cars due to the amount of electronics in them. Just as a question ... did the install of it bring down your insurance significantly. My lad had one on his fist car years ago and it kept his policy low, mind you it was only a Ford KA but a little pocket rust rocket 😀

I almost compared every insurance company i can find onlin/offline. Black box always are the cheapest ones. Giving 20~30% cheaper, i.e. ~£400 cheaper in my case, Admiral blackbox vs Admiral. I am thoes who dont really think they will use the black box to "listen" or "spying" my personal info because I know the device very well since i am an eletronic engineer. I also happy to have a "invisible" car tracker for free 🙂

Although I am yong, I am not addicted to the gas paddle, but the smooth transmission, silence, comfort and the leather sofa ... that Lexus provided. We just had a second rounds to NC500 last summer, that was the best time in 2020. That is also why I dont mind whether the black box will record my speeding.. it is very rare I did.

Long story:

I brought IS220D when i was a student (<25yo), switched to IS250 a year half later, but have not changed the insurance company.

The first qoute was ~£1100 for (10months, a term), but they later called back and asked for £1600 because my license just upgraded to manual (was automatic for 1.5y). But i argued that i already mentioned it when in the call. So the first term ended up at £1100. while other company asked for ~£1900

After that, when each term ends, they gave a qoute similar the the previous year, i.e. £1100 for the second term. I called their "cancelling department" at every renewal, to negotiate the price. The best price is always at 80% of the original renewal price. Now this is the sixth term I with them, and this term cost £250, even less than the road tax, despite I claimed for a windshield last year replacement which cost them ~£500. To be honest, I am quite happy with them. 😆

I can just disable it because the car is nolonger in the black box policy. There is a minimum premium £600 to be able to use.

It drain very little power when the service was activated. After they stop the service, the tracker keep searching for network which drains more power.

 

On 1/15/2021 at 2:55 PM, Linas.P said:

My first insurance with Bell had 3 months black-box. At the time I was 25 and it took insurance premium from £2800, to ~£2200.

But after that (very first insurance) there are no difference whenever it is with black-box or not. So yes, for younger driver and for first insurance it could reduce premium, but not as much as they advertise.

As well my blackbox was just plugged into cigarette lighter / 12V socket and it is only powered when engine is on or ignition is on. So I expected no parasitic drain from it - I would have never agreed to hardwired box.

Bell is also an Admiral's group company. Bell's black box is much better than others who require to install it in the car. 

It only require people to plug in for 3 months, and it doesnt drains power after the car switch off (exception for some BMW) 

 

 

[Aircheese]

Back to the topic..

Just test the CDS fuse with A/C on. It didnt drain more power than A/C off.

When I unplugged the CDS fuse, radiator fans is still working. So I assume if the fuse indeed controlling A/C, it might be the condensor fans only. I didnt have enough time to test the A/C. Maybe the temperature is too cold for AC to "condense".

I think I will keep the fuse off during the lockdown when the car is parked. Further investigation will not be necessary until the weather getting warmer again.

 

This show a different circuit than this previous post. Which I agree because the 10A is too small for the large radiator fan.

On 1/11/2021 at 7:03 PM, Aircheese said:

Thanks for the info, I just found the CDS in the manual in another separated pdf document. But still i couldnt locat it in eletrical diagram.

It is indeed related to a fan but i am quite confused between condenser fans vs radiator fans. Looks like the CDS supply the current.