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Overnight battery drain


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Hi Ted

welcome to the forum.

Difficult to give a precise answer without seeing the car but do the following.

There should be 4 (or more) uses as standard.  Remove one at a time and check for current flow with a Multimeter.

If you do not have a meter. Then remove one fuse per night and see which circuit caused the drain.

 

Roger

 

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Something you have left connected I expect. 

Welcome to the forums Ted.  A few more details would help - what is the car, what mods or extras are there on it , that sort of thing. 

Batteries can fail internally so that they self-discharge.  An alternator with a faulty rectifier can draw a current...... Lots of possibilities. 

Does the car have an ammeter? If so what does that read with everything switched off? 

 

Edited by RobH
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  • John Morrison changed the title to Overnight battery drain

Hi Ted, welcome to our forum.

I,ve changed the title of your post, to hopefully better target responses,

hope this is OK?

John.

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Hi Ted

If you remove a battery lead and put a test lamp in between the battery post and lead it will glow dimly then as you isolate each circuit, start by removing a fuse one at a time, then unplug the alternator etc when the light goes out that’s the circuit you need to investigate 

Chris

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5 hours ago, rcreweread said:

If you have a light in the boot, check it is going out when you close the lid

cheers Rich

+1. If it happened suddenly it's something left on unobserved like a boot or glove box light.

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Thank you so much for raising this issue.

I've had this problem for many years with my TR6 (I always disconnect the battery overnight, using a 'Dis-car-nect' cut off switch), & using Chris' tips, I've now established that the battery is draining  because of the 'Kenlowe' electric fan. It seems that the fan is earthing through its' relay (this is the wire that I'm dis-conneceting to make my test lamp go out, as in Chris' instruction.);

Do I now need to clean up/ upgrade the earth connection on the fan unit itself?

Many thanks,

Paul.

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26 minutes ago, TR Paul said:

Do I now need to clean up/ upgrade the earth connection on the fan unit itself?

No that won't help.  What you do to cure this depends on how things are wired but it sounds as though either the 'relay' or a switch (if there is one) may be faulty. 

Do you have a circuit diagram of the installation?  Is it like this:

Kenlowe+3of5.JPG

Is there a fan warning lamp which stays on? 

Is the fan working properly and cutting in and out with engine temperature?

 

 

 

Edited by RobH
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Hi Rob, thanks for your prompt reply.

The fan is wired through a relay: live feed is from a spare connector on the fuse box, the 'other side' of the side light fuse, switched from a non-adjustable thermostatic switch in the bottom hose(TRGB), with an override switch on the dashboard (with a lamp). The 'stat cuts in at quite high temperatures, and is more of a fail-safe, as I tend to use the override switch before I get into trouble. The fan was fitted by a P.O. with the Kenlowe adjustable thermostat (also, believe it or not,the P.O. had wired the fan so it  was 'sharing' the overdrive relay......!), as in your diagram. This Kenlowe 'stat  failed,so I replaced it with the system I've described. I've replaced the relay 2 or 3 times over 16+ yrs of ownership (they don't make 'em like they used to). The only potential 'clue' here is that the relay clicks when I re-connect the battery...?

Hope this makes some sense..!?

Many thanks,

Paul

 

Edited by TR Paul
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If the relay clicks it is getting current to the operating coil , so either there is a short circuit in the wiring or the thermal switch may have failed closed.   (Though you would expect the fan to run continuously in that case - maybe the relay has failed again also ?  ).   The current to the relay may be enough to drain the battery over a week or so. 

If you take the wire off the thermal switch and try your test again, if the relay 'click' has gone the thermal switch is faulty.  If it's still there, there is something in the wiring or override switch doing it. 

 

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Hi Rob

I will bow to your better knowledge of electrics but Paul says the relay clicks when he reconnects the battery. On your diagram it says power should be controlled by the ignition switch. If ignition is off then relay should not click when battery connected. Is it possible the power is from a connection on the fuse box   (side light fuse) that is always live even when ignition is off?

Keith

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Is the fused supply constant or ignition fed? If constant l would change to ignition fed so the circuit is only live when the ignition is on or engine running 

Chris

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48 minutes ago, keith1948 said:

I will bow to your better knowledge of electrics but Paul says the relay clicks when he reconnects the battery. On your diagram it says power should be controlled by the ignition switch.

That diagram is the Kenlowe one and I would not recommend doing it that way - that was just trying to find out what Paul has in case it followed that diagram.

By his description it is rather different. 

 

Chris is correct in that it would be preferable for the relay-coil side of things to be ignition-switched.  However the high current side which powers the motor itself should not,  as the motor starting current can damage the ignition switch, which is why a relay is used. 

(Some people prefer the fan circuit to be always powered, so that there is over-run after stopping the car until the engine cools, as with a 'modern'.) 

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As Rob says, I used the side light fuse, so the fan can be used with the ignition off, on purpose, so it can be used in hot weather at petrol stations etc, I have always done this with previous cars (A30/A35s, Spridget- all fairly basic cars) I've fitted electric fans to. TRoy (my TR6) is the first car i've owned with a 'proper' Kenlowe fan. All the others, I used fans sourced from scrapyards, with just a basic on-off switch (but I've always used a relay). This is the first car I've experienced this problem with.

This problem has existed as long as I've owned the car. The wiring, relays & sensors have changed over the years, the only constant being the fan itself. 

Many thanks for your continued interest & support, 

Cheers,

Paul.

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49 minutes ago, TR Paul said:

The wiring, relays & sensors have changed over the years, the only constant being the fan itself. 

The fan cannot draw current if the relay isn't operated, so it's difficult to see how the fan itself could be doing this.  Maybe the warning lamp in the circuit  is wired in such a way as to somehow pass enough current to make the relay click but not enough to close the contacts.......

Is the override switch the type which has the lamp built-in so the switch has three tags ? Is it wired to supply or to earth ? 

 

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Hi Rob,

The Lamp is seperate from the switch, and is wired from the fan & to earth (there is a 'proper' earth connection on the fan as well), so that it illuminates whenever the fan is on, whether activated by the switch, or the sensor - it will glow if the fan is being turned by the air rushing through the grill, on a late night fast run.

Cheers,

Paul.

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Hi Rob, that looks about right to me,  

cheers,

Paul

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In that case the relay 'click' must be something to do with the override switch, the thermal switch or the wiring around them. Really the only other thing could be a fault inside the relay but as you say, you have changed that.

Of course, that is assuming that the click is actually related to the the current drain......

If you pull the wire off  86 on the relay (might be 85 on yours - 85/86 can be either way round) the relay cannot operate, so there should be no drain when you do Chris's test. 

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Thanks Rob, i will commence an investigation. Your guidance has been much appreciated.

Cheers,

Paul.

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Good morning, i've investigated the relay wiring for the electric fan on my TR6, it was as follows-  30/87-fan/switch etc, 85 & 87- live, 86-earth (I'm not clever enough to upload a diagram!) quite different to your diagram, Rob. I have  now re-connected the wires in the same manner as you have shown me Rob; the test lamp now glows (rather than going out altogether) when I carry out the test, as was suggested by Chris. I haven't ran the car since Wednesday afternoon, & probably won't 'til this Tuesday or Wednesday (although the boot lamp still gives a healthy glow when I open it!), so the proof of the pudding will be in the eating!

Cheers,

Paul

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On 6/8/2024 at 11:18 AM, TR Paul said:

Thank you so much for raising this issue.

I've had this problem for many years with my TR6 (I always disconnect the battery overnight, using a 'Dis-car-nect' cut off switch), & using Chris' tips, I've now established that the battery is draining  because of the 'Kenlowe' electric fan. It seems that the fan is earthing through its' relay (this is the wire that I'm dis-conneceting to make my test lamp go out, as in Chris' instruction.);

Do I now need to clean up/ upgrade the earth connection on the fan unit itself?

Many thanks,

Paul.

+1 for the Dis-car-nect; fitted mainly because there are times of the year when my car doesn’t do a lot of miles, but I have noticed excessive fan overrun too. Should probably get round to having a look armed with the excellent intel (as ever) on this thread, but the Dis-car-nect works so well I never quite get round to it…

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I think you still have a problem Paul    If the test lamp lights at all, there must still be a battery drain somewhere.   If it doesn't go out when you disconnect power to the  fan circuit, then that one is no longer the culprit  - but there must be another circuit leaking current else the lamp will not glow.   

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Ok, thanks Rob, I shall get investigating again- in between  getting sorted for the IWE.  As Charlie says thank heavens for heavens for 'Dis-car-nect'.

Cheers,

Paul.

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