Blown ECU

[DavidElena]

I would appreciate some advice on what is looking like a cooked ECU. Due to a flat battery this week I started the car on jump leads, it ran OK until I disconnected them (I guess now in the wrong order) when the engine cut out and hasn't started since. The fuel pump isn't priming when the key is turned and the ECM fuse blows every time an attempt is made to start the car. I blew several other fuses, which I've replaced and the headlight bulbs (which locked the headlights into the up position). I've had good local auto electrician look at the car and he's pretty certain that that the main problem is a cooked ECU. Unfortunately, this is as far as he says he can take it and recommends going to a main dealer which for me in North Lincs is probably Leeds.

So is there a better way to go about this?

1. Can anybody recommend somebody that I can send the ECU to for diagnostics and potentially repair?

2. I read about the Elan scan, in this case where I can't energise the circuit will Elan Scan be able to give me any diagnostics?

3. If it does need to be replaced is it a part that can just be ordered and plugged in or does it need specialist set up by Main Dealer?

4. I'm wondering whether I should take the opportunity to upgrade the chip if I have to replace the unit, reading the threads I see everest is popular, are there any major problems with upgrading the chip?

5. Reading through the threads I see ESM (Alan?) seems to be the ECU/Chipping Expert and the main supplier for the upgrade chips. Alan can you help me?

Thanks.

[ailwyn]

2. I read about the Elan scan, in this case where I can't energise the circuit will Elan Scan be able to give me any diagnostics?

No, the ECU has to be in working order for Elanscan to work.

Does the check engine light come on when you turn on the ignition? Does the fuse blow at ignition on or when you hit the starter?

3. If it does need to be replaced is it a part that can
just be ordered and plugged in or does it need specialist set up by Main Dealer?

As far as I know you just need to take the one out, find out which memcal you need - I think this is usually printed on a label attached to the ECU (but am not certain). So that you can order an ECU and have the correct memcal.

4. I'm wondering whether I should take the opportunity to upgrade the chip if I have to replace the unit, reading the threads I see everest is popular, are there any major problems with upgrading the chip?

No problems with upgrading the chip. I think the ECU itself is standard for Elans, the chip with the software on is the difference, so in theory you could buy any Elan ECU and the correct Everest chip for your model (SE/S2/Fed derivative).

5. Reading through the threads I see ESM (Alan?) seems to be the ECU/Chipping Expert and the main supplier for the upgrade chips.

Alan is the only supplier as it's his chip(s).

If you can provide the information I asked for above then people may be able to offer more of a diagnosis of your problem.

Ailwyn

[DavidElena]

Ailwyn, thanks for the reply. There have been a few developments this evening which probably suggest that the ECU is actually OK and I seem to have an overcharging problem which is blowing the ECU fuse.

To check when the ECU fuse was actually blowing I put a new 10A fuse in and connected the battery. Turned the ignition a couple of clicks to check whether the fuse blew at that stage and was surprised to hear the fuel pump prime which it hadn't done before.

So turned the ignition the final click and the engine started !!, well for a few seconds at least before it stopped again. Checked the ECU fuse and it had blown. Put my last 10A fuse in and started again and it ran for about 20 seconds before I saw a spark down in the footwell as the fuse blew again.

However, this was enough time to realise that the battery voltage gauge was top scale at over 16 Volts (needle basically couldn't move any further).

So it looks at though the ECU fuse is doing its job in protecting the ECU and as the engine runs presumably the ECU is actually OK (phew).

I had a new alternator fitted a few months ago but I guess the voltage regulator is the bigger suspect? Can be susceptible to damage during jump starting.

The original problem was a sudden flat battery, fine in the morning, completely dead in the afternoon (lights not left on or anything obvious). Can a faulty alternator draw current when the engine is switched off?

I'm obviously glad that the ECU looks OK but I'm still interested in rechipping. Do you just place an order with Alan and follow the installation instructions?

Thanks again for your help, if I had followed the advice of the auto electrician it would have been on its way on the back of a truck to a Dealer to change the ECU!

[GeoffSmith]

The original problem was a sudden flat battery, fine in the morning, completely dead in the afternoon (lights not left on or anything obvious). Can a faulty alternator draw current when the engine is switched off?

David,

Sorry I've just noticed your post but the first question I was going to ask was "why were you jump starting it?" Candles had a similar problem after replacing an alternator - could you post details of the replacement alternator as it might act as a warning to others.

I think that what has happened is that your replacement alternator regulator pack has blown, which has then discharged the battery through the alternator windings. When you jump started the car, the alternator has not been regulating properly, but the load of the second battery has avoided the voltage going too high. When you removed the jump lead, the load decreased, the volts went too high and the fuze went.

BTW, the reason for removing jump leads chassis-first is for safety: if the live lead is inadvertantly dropped or touched on the second vehicle, there is not a short circuit and no sparks.

In general, if a fuze blows there is usually a reason for it to blow. Try and find out why, rather than putting another fuze in, because, as you found out, the chances are it will blow again and there is a danger of damaging something expensive. From what I have seen, the ECU is pretty well protected so hopefully you haven't damaged it.

A final point, Candles thought his headlamp module had blown as his headlights wouldn't work properly. It turned out to be that the headlamps had both blown due to the high voltage and the module needs at least one working headlight to complete the motor drive circuits. Even though you've replaced your headlamps, if they don't work properly, you know why.

Good luck with the alternator as it seems a bitch of a job to replace.

Geoff

PS I'm sorry to say it, but your auto electrician should have been able to diagnose the alternator fault.

[ESM]

The autoelectrician didn't earn his money then....

[GeoffSmith]

The autoelectrician didn't earn his money then....

Well I haven't got paid yet!

[DavidElena]

Sorry for the delay in replying I haven't had Internet access for a couple of days (now in Cornwall for a week). Indeed, the problem with the battery was very sudden. The battery was new a few months ago (pre-emptive in response to charge light/rough running issues which were finally traced to the alternator which was replaced). The battery/alternator has been fine for the last few months but then suddenly after work one day the battery was dead with insufficent charge for the courtesy light. There was no indication of lazy starting in the morning and I'm pretty sure I didn't leave the lights on.

When recharged the battery holds its charge when not in the car but when connected up it discharges overnight. It seems therefore that the battery is OK but there is a drain whilst the engine is not on. I only measure a draw of 30 mA though which to me seems pretty low but the explanation mentioned certainly fits the symptoms - I'll confirm once I've got to the bottom of it.

The new alternator was installed by a local garage. After reading a few LEC threads it wasn't a job I fancied tackling myself and I needed the car back quickly at the time. Therefore I'm not sure who supplied the unit but I'll try to find out and the post info hopefully with a final explanation of the problem which I hope is the regulator rather than alternator (hope Santa brings a new one tonight). From some of the threads it sounds as though the regulator is a little easier to get to. I should be able to progress again in a week or two when I get back home.

Once I've fully sorted the headlights I'll summarise that in a post as well, it's not immediately obvious when faced with headlight motors that won't respond anymore that the problem is simply one of blown bulbs.

Thanks again for the comments and help.

[GeoffSmith]

David,

You're right, 30mA should not kill the battery overnight (total charge <1Amp.hour which is squit all) so either the source of the discharge was not evident when you took the reading or the battery is knackered.

You could get the battery checked out under full load conditions or you could try drawing a similar current to what you think the car is drawing - a standard 100W mains light should take about 20mA.

Another thought is that there could be a thermal problem with the alternator - if you returned home and measured a low current then left it, the under bonnet/hood temperature can increase significantly which can affect electronics significantly.

Geoff

[ESM]

Check that the boot light isn't staying on - it is frequently is the cause of battery discharge

[DeanG]

My problems with a drained battery were due to having the light built into the mirror on. Since I cover the car and rarely drive it at night it took quite a while to find the "fault".

[mikeydude]

Hey Alan....when I bought my elan it had that exact same problem...boot light staying on...I eventually added a spacer to the lever that operates the switch to ensure it operated when the boot closed

[Ekapol]

Check that the boot light isn't staying on - it is frequently is the cause of battery discharge

The previous owner had it unplugged for me since day one. I think that might be a better way to go.

[Candles]

Sorry to wade in here late. I only just spotted the thread.

If you have overvolts indicated, the only places the fault can lie are the voltmeter or the regulator on the back of the alternator. If you have symptoms like yours, then chances are the voltmeter is working OK.

Unfortunately, changing the regulator is just as hard as changing the alternator. What you need to do is take it back to the garage that did the work and tell them that the alternator they fitted is broken already and they need to fix it. They'll squirm and try and tell you that you've blown it with a dodgy battery, at which point you can suggest they test it.

In the end, one of you will end up paying for the alternator to be removed and a new one fitted, that is bench tested and proven to be working. Then and only then will the car be OK.

And yes, a faulty voltage reg can drain the battery.

Sorry not to bear any seasonal good news!

Candles.

[DavidElena]

Unfortunately the thread title is pretty misleading now but just to wrap up the thread the problem was indeed traced to a faulty alternator/regulator. The unit had only been replaced a few months ago and a replacement was supplied free of charge but I paid half the labour to (re)install which is a half day job. The unit sourced was apparently a 'Cargo' alternator supplied by the local factors and apparently compatible with the car.

The overcharging was blowing the headlight bulbs and ECU fuse which is why it was originally mistakenly linked with the ECU itself. From the comments people have made it sounds as though this regulator fault is also likely to be the original cause of the sudden battery drain.

As Candles has described in previous threads if the headlight bulbs blow, the motor circuits don't work. The final irregularity was with a headlight control unit/relay apparently located at the front of the bulkhead. Even with bulbs replaced one headlight was just moving a couple of inches and not fully lifting or dropping and the other one didn't move. After replacement of this unit it's all sorted.

Thanks to Candles, Geoff, ESM, Ailwyn and others who helped with this problem.

[GeoffSmith]

David,

Glad to hear you got it sorted relatively cheaply, mind you Candles can do an alternator replacement in 2 hour flat.

If you still have the U/S headlight module, I'd be interested in seeing if I can find out what the failure mode is (I've already had Candle's spare apart). Please don't throw it away!

Geoff

[DavidElena]

Geoff, I've asked the garage who replaced the headlight control unit to retrieve it from their bin. I'll try to get over at the weekend and collect it. If you can send me a PM or E-Mail with your address I'll send it on.

The new unit came from Pat at Kelvedon motors. Apparently it was the second such unit he had sold that day so it sounds like a pretty unreliable item.

[GeoffSmith]

David,

The module has arrived thank you very much and the smell of charred MOSFET is now stinking out my loft! There was obviously a fair bit of heat dissipated but, encouragingly, it looks like it is only the one device that has failed and is worth trying a £1.20 replacement when I've got time.

Geoff

[DavidElena]

Good luck Geoff, new unit was about £80 so worth a try. I'm intrigued to find out what happens when you ignore the 'do not try to repair' label, it could be like the bit from Raiders of the lost ark when they open the ark.

[paulwatkins]

I'm intrigued to find out what happens when you ignore the 'do not try to repair' label, it could be like the bit from Raiders of the lost ark when they open the ark.

I'm kinda guessing that the 'do not repair' message is an attempt to put people off trying a repair that could only cost £1.20, when they can selll you a lovely new replacement part for £80!

[Sy V]

David

Where did you secure a replacement ECU from, for only £80?