Overheating while running A/C

[0-60motorsports]

How is the aux fan supply good? What did you measure and how?

Your are still fixated on the amperage for some reason.

So what should I do? I am only reporting back what they are telling me. Even swapped in a new aux fan and it made zero difference. Covid is not making it easy to get things done or get info especially when we have a shut down in effect right now which will end on the 25th

[sapote]

The voltage is at 13.8- 14.1 so the issue is not the charging system, .

Read post #85 , even with 14v charging, the fan could still run slow if .....

[Shonky]

So what should I do? I am only reporting back what they are telling me. Even swapped in a new aux fan and it made zero difference. Covid is not making it easy to get things done or get info especially when we have a shut down in effect right now which will end on the 25th

Well the problem is being a middle man it would seem. You ask for advice here and we give our ideas. However some simple things we suggest don't seem to happen so either your shop is not doing them or the full message is not passed on. I can understand they might not want to listen to the customer.

Seems like your shop just wants to replace parts more than diagnose the actual problem. You say the fan power supply was tested. How was it tested?

You seem convinced it is aux fan related (and there's not even a guarantee of that). Measure the actual power (i.e. voltage and current) to the fan *at the fan* and compare that with and without the donor car connected. This has already been suggested, but you come back with "the aux fan power supply is ok, and we replaced the fan anyway". No one here suggested replacing the fan yet. Or measure the speed as suggested. Do that with and without the donor car/power supply. If the fan speed or its power input changes (and the car cools down), you at least know you're on the right track. Fans are pretty simple things

The current measurement at the battery I'm not sure is even helpful. All that tells you is what is going to or from the battery. I don't know the exact wiring but that would not be supplying any devices at the front of the car. I don't see how your load/no load measurements really reflect the alternator's output. Even then, if you have 60A running into the battery for extended periods (assuming -ve is charging the battery with your clamp), then something else would seem wrong. That's a lot of energy going into a battery.

Without me re-reading the whole thread are you sure your temperature measurement is correct? i.e. there's no chance that something electrical is causing the temperature to read high?

[sapote]

if you have 60A running into the battery for extended periods (assuming -ve is charging the battery with your clamp), then something else would seem wrong. That's a lot of energy going into a battery.

Good point, as I also overlooked the 60A measurement at the battery cable. This is not normal for either the current flow out, or into the battery, with engine running. I remember OP even said donor car had close to 100A, at the battery cable too? This can't be true.

[0-60motorsports]

Guys I appreciate all your advice but Covid and shut down are leading to my hands being tied right now and not able to get your suggestions implemented properly. I’ll post back when I can physically go to the shop and have all the tests done in the right way (some things get lost in translation too). That’ll be in 10-15 days.

[0-60motorsports]

Well shutdowns over, back at it lol…. Will update when I have something.

[0-60motorsports]

Nothing to update, We still have not been able to find the cause of the amperage drain and this is what i suspect caused damage to the previous DME and is causing a slight misfire. When another running car is connected to my car and amps go up to near a 100 the misfire goes away immediately and temps drop as aux fan is getting full electrical juice to run at top speed.

to be honest I have given up and have decided to just the park the car up and thats that......we'll see if or when i ever touch it again. Honestly its just just shit that no one could find the issue from my side.

[Shonky]

I can only reiterate my previous posts with regards to our suggestions. The basics still don't seem to be covered. I'm somewhat intrigued by your problem but it's frustrating to make suggestions that are fairly simple to implement yet ignored.

Why would your DME be damaged now? Why would it run fine with an external supply if it was damaged?

[0-60motorsports]

I can only reiterate my previous posts with regards to our suggestions. The basics still don't seem to be covered. I'm somewhat intrigued by your problem but it's frustrating to make suggestions that are fairly simple to implement yet ignored.

Why would your DME be damaged now? Why would it run fine with an external supply if it was damaged?

I followed everyone's advice. We checked everything. Do not forget there are three highly experienced master techs (BMW Certified etc.) the issues is still amp related and not voltage related.

The car was acting weird and jerking around and i swapped DME's as I had a spare one and it has the exact same mods and tune on it and the car has been fine ever since. If the cars not making enough electrical power of course i will start damaging modules and thats what i am sure damaged the previous DME and is causing my misfire.

We even tried different engine, spark plug, ground cables/harnesses from a an M3 that was making the correct amperage etc.

[Shonky]

I followed everyone's advice. We checked everything. Do not forget there are three highly experienced master techs (BMW Certified etc.) the issues is still amp related and not voltage related.

The car was acting weird and jerking around and i swapped DME's as I had a spare one and it has the exact same mods and tune on it and the car has been fine ever since. If the cars not making enough electrical power of course i will start damaging modules and thats what i am sure damaged the previous DME and is causing my misfire.

We even tried different engine, spark plug, ground cables/harnesses from a an M3 that was making the correct amperage etc.

To be blunt:

You have three experts who haven't fixed the problem. If they're so great then why are you on the forum asking for help?

Do you understand "amp related" doesn't really mean anything. Ultimately most circuits will draw current based on voltage. Amps is largely secondary to voltage.

Lack of "electrical power" is unlikely to start damaging modules. Do you understand what you're even saying by that?

So a DME swap may have fixed the problem (except you also just said the problem isn't fixed?). So what about the alternator that you were obsessing about?

[0-60motorsports]

To be blunt:

You have three experts who haven't fixed the problem. If they're so great then why are you on the forum asking for help?

Do you understand "amp related" doesn't really mean anything. Ultimately most circuits will draw current based on voltage. Amps is largely secondary to voltage.

Lack of "electrical power" is unlikely to start damaging modules. Do you understand what you're even saying by that?

So a DME swap may have fixed the problem (except you also just said the problem isn't fixed?). So what about the alternator that you were obsessing about?

Thanks for your polite advice.

[sapote]

Shonky sapote Thank you for your insight and I will pass it on to the techs.....I'll keep you guys updated. Mean time here is the read out with and without load.

Without load



With Load

No load => 29A
With load => 64A
what does this mean? Are these the current flow out (discharge) or into the batt (charging)? I say it is the discharge current because with load, the voltage at the batt must be lower and not higher and so the discharge is higher.
OP, remind us what is the load? Is it the AC turned on load? If without load and the batt was discharged at 29A then your battery soon would be empty. Do you have battery discharged issue?

[sapote]

Nothing to update, We still have not been able to find the cause of the amperage drain and this is what i suspect caused damage to the previous DME and is causing a slight misfire. When another running car is connected to my car and amps go up to near a 100 the misfire goes away immediately and temps drop as aux fan is getting full electrical juice to run at top speed..

Do you have dead battery with this high drain current, as I don't remember reading about dead battery?
Where was the 100A current measured at -- on the jump cables connected to the other running car or at your red battery cable? If it was at the other running car, then your car suck out 100A from the other car in addition to your alternator supply which should be more than 100A. This means there is a bad connection that drains more than 200A in your car.

With such high load current, the system voltage should be lower than normal of 14V. Normally with lower current, there should be less chances of components (DME etc. )being damaged as compared to higher voltage. However, if this high load current is intermittently on/off , this can cause a phenomenon which is load-dump, and a large load-dump can cause a huge voltage spike on the cables and this could damage the components.

[sapote]

0-60motorsports:

You hijacked this thread and I thought you're the OP -- confused. Should create your own thread.
So previously I said the 29 and 64A was the discharge current, but after review your posts again I didn't see you mentioned about dead battery issue. So I thought again -- are they charging or discharging currents?

Looking at this pic. It has 2 red cables to the battery. The bigger one (being measured) connected to the starter and alternator, and the smaller one connected to the rest of the car. So I was wrong in saying those currents were discharging from the battery. With more load, there was more current flowing out on the smaller cable from the battery post, and so the alternator increased more current (69A ) to the battery via the larger cable. This design is a little odd and will waste more energy as the alternator high current has to flow twice the length of the car: from alternator to battery and then from battery to the load which is mostly at the front. But I think it had to be done this way in order for the BMW engineers to add the BST (battery safety terminal? to cut off the current in an accident).


For our cars, the alternator is spec at 120A max current. If your car suck out the other running car 100A in addition of your own 120A, then whatever the load on your car needs about 220A which is very large and should be easily be narrowed down to that component. Ask your mechanics to use the same current-meter and check on the thick wires coming to the fuse boxes. Start at those high current fuses first.

[0-60motorsports]

Just an update, problem Solved. Bad alternator. Replaced with 140AMP X5 alternator and coolant temps are max of 93c (and drop) in 125f indicated weather temps. This with AC om Auto set at 20-21c.