Parasitic battery drain on a Mk 2.5

Does anyone know whet the parasitic drain on a Mk 2.5 should be?

Having just replaced my battery with a Panasonic battery after it suddenly failed on me, I don’t want the new one to go the same way because of an excessive drain.

I understand a Mk 1 runs at about 23-24mA but I measured mine at 35-36mA, although it was fluctuating and I briefly saw 6A at one point, although that may have been because the battery had only just been fitted and I didn’t give it a chance to settle down.  Is this normal on a Mk 2.5?

Hi Keith I found

this old thread on the subject 

If you google ‘parasitic drain MX5 MK2.5’

or ‘dark current MX5 MK2.5’ you will find lots of references.

I looked at quite a few but limited expression of the expected drain from a MK2.5 clearly spelled out in milliamps.

This info is quite important so would be nice if some MK2.5 owners could provide theirs. Will probably need to extend the connectors and shut the boot to test on this car(not necessary on the MK1).

I think you will find that the room fuse is the key to parasitic drain, so remove that and it will probably be zero. The room fuse protects a lot of circuits on the MK2.5, so finding the one responsible may take some time. This car has a factory alarm fitted which may account for the amount above that standard on the MK1 - again lets hope for feedback from a MK2.5 owner as I do not have one here at the moment to test.  

In truth 35/36 ma will not cause you a problem, particularly if the car in regular use.

Our Eunos, generally in daily use had a reading nearer 200ma because of a dodgy stereo and only showed a battery problem when car left undriven for a period of time.        

Mine seems to be above the .20 ma figure, more often than not. A battery running low will also supply more current, though not the case on a new fully charged battery. Did you go for a good drive before checking the parasitic drain - in case the battery was in storage for some time, so it needs bringing up to fully charged?

Mine is generally used twice a week, and for short drives only these days, but the battery holds up well enough for those starting cycles, but - the winter is the worst - I had to recharge my batter twice last winter.
Batteries do not like the cold, nor do electrics, wiring and fittings draw more current when it’s cold then when it’s warmer. In wintertime, my battery from fully charged is good for about ten days maximum, but it’s rarely fully charged, hence the need for recharging. - so ten days drops to not more than 7-8 days.

According to Robbie - a Mk2.5 is rated at 20 - 24 ma ‘dark current’ (The current drawn when the car is not in use.) Mine seems more like 30-35 ma, which eould agree with your reading. I put this down to the alarm, the back up battery in the ECU (PCM) and Radio clock and memory back up. Apart from the immobiliser, which may or may not draw current when the car is otherwise ‘dead’ (unused). - None of this is clear, but an assumption on my part. (my wiring manual is fill of ? ‘empty boxes’ where hidden circuits exist. - I have to guess what they do!)

If you were checking the drain with the boot lid open, and reading between either battery lead and battery itself, then you would read greater current, due to 1) boot light lit, and 2) alarm is set at stage 1 (boot lid open) which would mean additional load. Wouldn’t expect that to reach 6 amp though, but that could have been a meter lead slipping? - Depends on meter quality, and the ‘dampening effect’- (poor meter dampening means the needle will swing about wildly when in use, and does not register a true reading immediately.
A digital meter is usually better in that sense. This is controlled on an analogue meter by that coiled spring you can see attached to the back of the needle. Most cheap meters are difficult to set at zero, which doesn’t help either. You set it one day, and a few days later it needs resetting again!

I did use an extension so I could close the boot and still read the current, and I am using a digital ammeter.  I need to retest and be a bit more patient to see if the current stabilises over time (i.e. the 6A peaks stop).  Then I need to start pulling fuses as Rob suggested to see if I can at least identify what may be responsible.

The car is in the garage at the moment so it will have to wait until it is back.

Thank you both for your input.  I will report further.

What make digital ammeter are you using? It is usually only expensive models that can read a value accurately at that low level . I think mr G’s 0.20 ma should be 0.02 ma.( 0.20 is 200 ma )

Don’t know how the dot got in there, but I did say ma. You are right though, it does read as 200 ma.