Electrical Problems - Alternator - Alarm - ECU

[andydckent]

OK we have a few problems here but I am beginning to suspect they are linked. I will try to summerise briefly.

1) Alarm sometimes won't arm and there is the sound or a relay clicking away inside when the doors are closed. Suspect reason is not enough power to activate relay. Result is weak battery after sitting all day or over the weekend. Final result flat battery this morning (was expecting this to happen). This has happened previously to repair event referred to in other two points.

Removed battery to recharge as considered it had never been fully charged since the car was off the road due to being written off and repaired by my dad and myself. Battery charges to good voltage.
Charged battery does not solve alarm relay clicking. Perhaps it will work if the alarms internal battery needs to charge for a while.

2) Check voltage across battery while car running. It is charging at 16v+. This is far to high. Suspect alternator is not regulating voltage correctly and could be causing other problems including the above. Suspect that is a result of the battery being connected the wrong way round when the car was being fixed as detailed in this post: http://www.clubvr4.com/forum/showthread.php?73239-Battery-connected-wrong-way-What-s-broken It could have happened since I suppose.

It's a cold spec alternator, assume that voltage regulator is built in and that the whole thing needs replaced?

3) Jerky auto box changes as detailed in this post have not fully gone away: http://www.clubvr4.com/forum/showthread.php?73418-Autobox-Jerky-change-4-to-5 This is despite correct fluid levels and ATF being in decent condition. I wonder if this could be a result of possible damage to ECU caused by battery connected wrong way around or by alternating overcharging? Or if the voltage in the battery has been draining enough to reset ecu?

Linking these things together but I think you'll see what I'm on about. Thoughts please?

Thanks

Andy

[TAR]

I would begin by resolving the issue with the alternator. The regulator can possibly be fixed by an auto electrician without the need to replace the whole thing. The alternator is a pain to remove due to lack of space.

A charge of 16V is possibly having a bad effect on the rest of the electrical system and may cause damage to other components.

The relay clicking would need further investigation to discover which relay it is. You say its an alarm one; what's it's purpose? A relay by itself would not draw much current in its operation but it may be drawing lots when supplying the switched component, which could be draining your battery.

The battery may also be knackered now even if it appears OK, it would need to be load tested to ensure all the cells are OK and it can supply current as rated. I think an auto electrician or Halfrauds could check that for you.
:happy:

[andydckent]

Hello

Thanks for the reply.

One small thing to investigate is whether the voltmeter is reading properly. I'm at work just now but my dad reports that he has just put the meter over the battery in his Colt and that it is also reading 16v while the engine is running. There is nothing to suggest that there was a problem with that car and I have read elsewhere that voltmeters with low batteries sometimes over read. Think we need to check that this isn't the case as it seems somewhat unlikely (but not impossible) that both cars have the same problem at the same time....

Andy

[andydckent]

On the alarm I'm not sure what the relay does as I've not dug behind the dash to find the unit. However, it starts to click as soon as the ignition is turned off and only stops clicking while the door is open.

[Davezj]

if you can fix it yourself or do not have the confidence to fix it then get an auto electrician in to fix it.
as long as they are a good recommended auto electrician then they should be able to fix. but there are a lot of people out there that call themselves auto electrician just because the bought a DVM. i would only use a personally recommended person not a checkatrade person or some other recommended a trade website, i am sorry but i have heard too many horror stories about checkatrade people writing their own reviews and paying to have reviews written.

however car electrics are not complicated you just have to be methodical in your approach and have so basic electronics knowledge and the proper tools for the job.

[andydckent]

OK so the good news is that after replacing the battery in the multimeter the voltages are 12.25 v engine off and 14.73 v engine idle. I think that means the alternator is not the problem.

[TAR]

The next thing I would do, is check that the battery is good. It may charge fine and look ok, but it could still fail under load.
This is known as a load test and is usually done with a piece of test equipment. As mentioned, Halfrauds may do a free check if you ask them.

Let us know how this goes.

:happy:

[Davezj]

OK so the good news is that after replacing the battery in the multimeter the voltages are 12.25 v engine off and 14.73 v engine idle. I think that means the alternator is not the problem.

that is good to hear, it sound like the alternator is fine.

[Nick Mann]

I'd suggest that a dodgy battery is likely to be at the heart of the problem.
If the voltage keeps dropping then the gearbox will never properly relearn the shifts.

[elnevio]

I would expect a healthy battery to be reading high 12s after charging?

[andydckent]

So after being left over night with relay clicking the voltage was down at about 12.15 v.

I did a crude 'load test' observing the lowest voltage while the engine was started and the voltage dropped down to somewhere in the 9 v range which is a bit low.

After 25 mins city driving this morning the battery voltage was 12.38 v.

The battery is one of the big yellow ABX AGM AX D26L ones. Anyone have experience of how long these last. It must be around 4 or 5 years old.

Thanks

Andy

[Z-Kev]

well a poorly agm battery will feck your alternator in short time, they have such capacity and capability that they will soak everything your alt is producing

[andydckent]

Battery was down at 12.05 v this morning. Did not attempt to start.

So is it the battery or the clicking alarm relay draining it or both?

I can have a dig behind the dash at the weekend to see if there is anything obviously loose on the alarm unit but should I just be buying a new battery?

[andydckent]

Think I'll just buy one and see if that solves the problem....

[andydckent]

OK so I've replaced the battery and lo and behold the alarm has started to work again. I reset the ecu so we will see if the gear box sorts out now too. I have another idea what it might be though to test out if it doesn't cure. Fuel cut or a leak in the pipework which is opening up and closing again.