Overheating while running A/C

[0-60motorsports]

Update:

So today we might have discovered the cause of the overheating. Message from my tech who has been working on my car for more than 14 years:


“Bro, something unbelievable in your car M3, I told them to keep the car engine running while under the sun, they did yesterday and when about to overheat put the battery jump start cable that connected from another car that the engine is running then it solve the overheating, the possible cause is weak alternator, the voltage is ok possible the amperage is low and due of a/c load the aux fan became not efficient to push more air.”

New valeo alternator ordered from FCPeuro.

[eacmen]

Update:

So today we might have discovered the cause of the overheating. Message from my tech who has been working on my car for more than 14 years:


“Bro, something unbelievable in your car M3, I told them to keep the car engine running while under the sun, they did yesterday and when about to overheat put the battery jump start cable that connected from another car that the engine is running then it solve the overheating, the possible cause is weak alternator, the voltage is ok possible the amperage is low and due of a/c load the aux fan became not efficient to push more air.”

New valeo alternator ordered from FCPeuro.

Nice find. I would expect the voltage to drop when the aux fan kicked on if this was the case.

[Ramo]

Update:

So today we might have discovered the cause of the overheating. Message from my tech who has been working on my car for more than 14 years:


“Bro, something unbelievable in your car M3, I told them to keep the car engine running while under the sun, they did yesterday and when about to overheat put the battery jump start cable that connected from another car that the engine is running then it solve the overheating, the possible cause is weak alternator, the voltage is ok possible the amperage is low and due of a/c load the aux fan became not efficient to push more air.”

New valeo alternator ordered from FCPeuro.

My battery wasn’t holding a charge anymore since it was around 7 years old so I replaced it. Once in a while I still get a “low battery” message on my uniden r3 radar detector even with the new battery and the car overheats (on hot days 95+) with the AC on. Wondering if it’s the alternator as well.

[0-60motorsports]

Another thing we were discussing is that I have and hasan from HTE have been running the CSL battery for a while. Me ten years. I switched to the bigger stock battery last year since the CSL battery wasn’t available at the time. My tech and we think that due to the smaller battery it effected the alternator life. We run AC almost all year around and it gets hot and humid here up to 125f. Just a theory.

[yhp2009]

Thats interesting for sure. BTW did you end up replacing the compressor as well? I remember that was where you left off last?

[0-60motorsports]

Thats interesting for sure. BTW did you end up replacing the compressor as well? I remember that was where you left off last?

Well No because it is working perfectly fine and my tech refused to in a way, which is good for my pocket. He really is great and the reason I have stuck with him for the past 14 years or so.

[yhp2009]

Well No because it is working perfectly fine and my tech refused to in a way, which is good for my pocket. He really is great and the reason I have stuck with him for the past 14 years or so.

Fair enough. Thanks again for keeping us updated and knock on wood for the new idea. If it is the alternator that would be a relief and a head scratcher for sure.

[0-60motorsports]

Fair enough. Thanks again for keeping us updated and knock on wood for the new idea. If it is the alternator that would be a relief and a head scratcher for sure.

Yes Sir, here to contribute as much as I can and to learn. Alternators on route, should be here in 4 days. In the meantime I’m going to install some purple solid subframe bushings lol

[WOLFN8TR]

My battery wasn’t holding a charge anymore since it was around 7 years old so I replaced it. Once in a while I still get a “low battery” message on my uniden r3 radar detector even with the new battery and the car overheats (on hot days 95+) with the AC on. Wondering if it’s the alternator as well.

Wow a 7 year old battery, got your money out of that one! It makes sense it could be the Alternator causing the overheating issue. It's kinda the same if the AC compressor was going bad causing extra load/drag on the system. Hope this solves the problem.

[S14]

Wow a 7 year old battery, got your money out of that one! It makes sense it could be the Alternator causing the overheating issue. It's kinda the same if the AC compressor was going bad causing extra load/drag on the system. Hope this solves the problem.

Are you saying the AC compressor drags and creates a load even when the AC isn't on and the compressor should be freewheeling?

[yhp2009]

Are you saying the AC compressor drags and creates a load even when the AC isn't on and the compressor should be freewheeling?

I think he meant that a bad alternator can have a similar effect as a bad compressor

[0-60motorsports]

So here’s an updated after installing a new valeo alternator and new original bmw waterpump, the car is running much better the amps have not gone up too much. Before the new alternator it was putting out 40amps and now around 79. I have another m3 here with 11000 miles and puts out above 100 amps.

The car now runs cooler in today’s 44c temps it was running 88c coolant temps so that’s normal
But when you go past half way mark on the blower fan it starts going up in heat back to around 96-98c coolant temps.

Any ideas guys? The only thing I haven’t changed is the ac compressor and I really don’t want to lol.

[0-60motorsports]

Update 1 Sept:

We might have discovered the cause of the overheating. Message from my tech who has been working on my car for more than 14 years:


“Bro, something unbelievable in your car M3, I told them to keep the car engine running while under the sun, they did yesterday and when about to overheat put the battery jump start cable that connected from another car that the engine is running then it solve the overheating, the possible cause is weak alternator, the voltage is ok possible the amperage is low and due of a/c load the aux fan became not efficient to push more air.”

New valeo alternator ordered from FCPeuro.

Update 17 Sept:

So here’s an updated after installing a new valeo alternator and new original bmw waterpump, the car is running much better the amps have not gone up too much. Before the new alternator it was putting out 40amps and now around 79. I have another m3 here with 11000 miles and puts out above 100 amps.

The car now runs cooler in today’s 44c temps it was running 88c coolant temps so that’s normal
But when you go past half way mark on the blower fan it starts going up in heat back to around 96-98c coolant temps.

Any ideas guys? The only thing I haven’t changed is the ac compressor and I really don’t want to lol.

Update 20 Sept:

Just to rule out the new valeo alternator as faulty we will swap a tested on car alternator from another M3 and see if it still behaves the same. Stay tuned lol.

[0-60motorsports]

Update 1 Sept:

We might have discovered the cause of the overheating. Message from my tech who has been working on my car for more than 14 years:


“Bro, something unbelievable in your car M3, I told them to keep the car engine running while under the sun, they did yesterday and when about to overheat put the battery jump start cable that connected from another car that the engine is running then it solve the overheating, the possible cause is weak alternator, the voltage is ok possible the amperage is low and due of a/c load the aux fan became not efficient to push more air.”

New valeo alternator ordered from FCPeuro.

Update 17 Sept:

So here’s an updated after installing a new valeo alternator and new original bmw waterpump, the car is running much better the amps have not gone up too much. Before the new alternator it was putting out 40amps and now around 79. I have another m3 here with 11000 miles and puts out above 100 amps.

The car now runs cooler in today’s 44c temps it was running 88c coolant temps so that’s normal
But when you go past half way mark on the blower fan it starts going up in heat back to around 96-98c coolant temps.

Any ideas guys? The only thing I haven’t changed is the ac compressor and I really don’t want to lol.

Update 20 Sept:

Just to rule out the new valeo alternator as faulty we will swap a tested on car alternator from another M3 and see if it still behaves the same. Stay tuned lol.

Well Guys, here we are a 9 months later and we still have the same issue and have not been able to find the cause of the car not generating enough amps or anything close to 80 amps that other E46 m3's are making. My M3 is still making 50% less and the strain is causing the over heating as it can not supply enough electrical power to the aux fan......

Anything else I can check as I have checked as much as I can so far. Problem is electrical and not mechanical.

[eacmen]

Well Guys, here we are a 9 months later and we still have the same issue and have not been able to find the cause of the car not generating enough amps or anything close to 80 amps that other E46 m3's are making. My M3 is still making 50% less and the strain is causing the over heating as it can not supply enough electrical power to the aux fan......

Anything else I can check as I have checked as much as I can so far. Problem is electrical and not mechanical.

Bad grounds.

Any thick cable on the car make sure the contact is clean and tight.