Parasitic battery drain Rover 75

[lida]

Hello Tony,

I had a parasitic drain some years back. It was traced to the sat nav. I had that removed, which solved the problem.

[Tony jr]

Originally Posted by SD1too

Hi Tony,

I don't think any of us can accurately predict what's going to happen when an input is removed from an ECU connected to multiplex systems.

To give an increased current draw the relay contacts would have to be stuck in the "made" position. This would result in the two pumps running continuously. You don't have that evidence.

I suggest that removing the fuel pumps fuse is not a useful test. Forget it and move on.

Does your car have sat. nav?

Simon

Hi Simon,

You are right I don’t have any evidence of the fuel pumps constantly running. The car is fitted with an aftermarket blaupunkt trafficmaster radio that appears to be still drawing 0.6 amps when switch off. Removing the radio fuse No. 33 drops the current drain down from 1.15 amps down to 0.52 amps. So the radio is contributing to roughly half of the parasitic drain. However, the residual 0.52 amp drain is still present even after leaving the car 30 minutes to shut down. I have not found a fuse that would drop this current down to an acceptable 0.05amps. I was hoping it would just be a case of identifying the circuit responsible and then homing in on the component causing the problem. Should have known better.

[SD1too]

Originally Posted by Tony jr

However, the residual 0.52 amp drain is still present even after leaving the car 30 minutes to shut down.

Tony, you might find steve-45's story interesting (he has a diesel too).

Simon

[Tony jr]

Originally Posted by SD1too

Tony, you might find steve-45's story interesting (he has a diesel too).

Simon

Thanks Simon it’s got to be worth a try.

[Tony jr]

Quick update,

I put the one clamp meter on the battery lead going to the fuse box (0.5 amp with the radio fuse out) and another clamp meter on the alternator battery lead (0.01 amp) pulled the plug on the wires going to the alternator rectifier pack and found no drop in current still 0.5 amp draw (fuse box lead) and only 10mA through the alternator battery lead. Would I be right in ruling out the alternator as the cause of the problem? If I disconnect fuse link 3 the current drops to 0.1Amp

[SD1too]

Originally Posted by Tony jr

If I disconnect fuse link 3 the current drops to 0.1Amp

Thanks for the update Tony. I'm glad that you haven't given up!

Looking at the wiring diagram FL3 (50 amps) feeds the passenger compartment fuse box. It splits into four connections each feeding a group of fuses:

• 28, 30, 32, 34, 36
• 29, 31, 33, 35
• 38, 40, 42, 44
• 47, 49, 51, 53

Simon

[Tony jr]

Originally Posted by SD1too

Thanks for the update Tony. I'm glad that you haven't given up!

Looking at the wiring diagram FL3 (50 amps) feeds the passenger compartment fuse box. It splits into four connections each feeding a group of fuses:

• 28, 30, 32, 34, 36
• 29, 31, 33, 35
• 38, 40, 42, 44
• 47, 49, 51, 53

Simon

Hi Simon,

Thanks for that. Is that 4 separate wire feeds from the fuse link3 in the engine compartment fuse box to the passenger compartment fuse box? Just wondering if one of the wires is shorting out between the fuse boxes

[SD1too]

Originally Posted by Tony jr

Is that 4 separate wire feeds from the fuse link3 in the engine compartment fuse box to the passenger compartment fuse box?

No Tony. The output of FL3 is on a single wire which en route splits into four wires, each connected to a separate pin on the passenger compartment fusebox connector.

Originally Posted by Tony jr

Just wondering if one of the wires is shorting out between the fuse boxes

No again! If it was, that would cause FL3 to blow which isn't the case. What you have isn't a short circuit or an open circuit, it's a malfunction of the multiplex wiring system causing a circuit to draw current when it should be "asleep". The difficulty we are having is identifying that circuit.

Simon

[drewbie]

Originally Posted by MSS

The systems in the car do not all shut down instantaneously. Have a look at my thread here.

https://www.the75andztclub.co.uk/for...d.php?t=315487

If shutting off a system by pulling the fuse wakes up another system the overall current consumption could increase.

You need to take a planned, systematic approach when searching for the source of current drain.

Hi, would you expect much the same results from all engine variants?

[MSS]

Originally Posted by drewbie

Hi, would you expect much the same results from all engine variants?

I would expect that all variants would have systems shutting down at different times but not at the same times as the diesel because some of the systems are not the same and even those that are may be configured differently.

Perhaps someone who has made measurements on the petrols can shed more light on exactly how the 1.8 and 2.5 behave?