Cooling fan runs on cold startup - this can't be right, right?

[Robert4604]

Hi, All -

My wonderful '15 TDI Golf has recently developed a weird habit. It's winter here in CO but I park my car inside a 50F garage. Sometimes I start it up to get some heat into the engine and cooling system before leaving. After a minute or two, I hear the idle rise, and I know what's going on - the coolant fan is running when all systems are pretty much stone cold - no A/C on, no defrost on, and I have the heater fan on the first position. I was under the impression that the radiator fan only runs when the car is up to 200F and needs additional cooling, which is not the case in my cold garage. I just ran Vag-com and cleared some miscellaneous codes, so everything is fine there. Does anyone know what the heck is going on here? I feel that I am wearing out my fan for no good reason. Thanks!
- Rob

 

[Nuje]

Could be that you shut it down mid-regen (DPF burning off accumulated soot), so it's trying to pick up where it left off (I'd think it would wait to get back up to operating temp to do so, though). Nonetheless, I'd take it out on the freeway for a 20min rip and see if that does anything.

Also: what were the "miscellaneous codes"? Anything in the 01-Engine module?

 

[Robert4604]

Hi, Nuje -
Possible mid-regen shutdown is what my pal the service manager at the local VW dealer said, as well. So, I immediately drove 20 highway miles last week at 75, and I am still here with this problem. This was probably 300 miles ago, regens don't happen that often, right?

 

[pedroYUL]

Regens happen around 200 miles apart for me.

 

[Robert4604]

OK, I am getting the picture. I'll do the standard 20-mile highway drive and report here on the result. Pedro, how do you know that you are doing a regen? Thanks, Pedro and Nuje!
- Rob

 

[pedroYUL]

My both CR cars actually shimmy at idle when a regen is happening, and the fans do run high speed at shut down to cool off the regen temps.

I actually never seen my cars run the fans because it's hot out, or maybe for a few seconds at shut down, but not for minutes... that's a regen.

 

[Shiboxtdi]

My both CR cars actually shimmy at idle when a regen is happening, and the fans do run high speed at shut down to cool off the regen temps.

I actually never seen my cars run the fans because it's hot out, or maybe for a few seconds at shut down, but not for minutes... that's a regen.

Sorry too interrupt what is regen

 

[pedroYUL]

Sorry too interrupt what is regen

In North America we started to get TDIs with Diesel Particulate Filter (DPF) at the same time technology changed to Common Rail (CR).
Every DPF needs to convert the soot it filters to ash, via a process called regeneration (regen).

 

[Shiboxtdi]

Ohhh okay I knew about all the emissions but I never heard the regen term thank you Pedro

 

[lemoncurd]

Sometimes I start it up to get some heat into the engine and cooling system before leaving

this wont do anything for diesels. diesels need to have load on them to heat up.

about the fans on high after cold start, some googling shows other people had similar issues because of a faulty AC pressure sensor or switch.

shutting the car down mid-regen, then turning it back on once it is totally stone cold will not make the fans run again. the car is smart enough to know it isnt in a regen cycle anymore.

you mention there where some misc codes, what where they specifically?

after you do this latest highway run, please post an autoscan of the vehicle.

 

[Robert4604]

Hi, Lemoncurd -

Mine heats up, or at least shows some temp on the gauge, in 10 minutes.

I did my standard 20 mile round-trip regen drive, and the next morning, cold (45F) in the garage, the fan started running in 45 seconds. I had no faults scanning the engine, but here is the HVAC:

Monday,15,January,2024,12:20:18:61379
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 11 x64
VCDS Version: 23.11.0.0 (x64) HEX-V2 CB: 0.4643.4
Data version: 20231027 DS351.0
www.Ross-Tech.com


VIN: 3VWRA7AU1FM092673 License Plate:
Mileage: Repair Order: 1/16/24



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Address 08: Auto HVAC Labels: 5G0-907-426.clb
Control Module Part Number: 5GM 907 426 A HW: 5GM 907 426 A
Component and/or Version: AC Manuell H02 1001
Software Coding: 00020104202100000000000000000000
Work Shop Code: WSC 01383 790 50316
ASAM Dataset: EV_ACManueBHBVW37X 003019 (VW37)
ROD: EV_ACManueBHBVW37X_003.rod
VCID: 46D65EA5C829110A55F-8012
2 Faults Found:

1048834 - Functional Limitation due to Energy Management
B10CD 00 [00001000] - -
[PTC-Reduzierung durch BCM]
Intermittent - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 7
Fault Frequency: 24
Reset counter: 18
Mileage: 107726 km
Date: 2024.01.03
Time: 20:31:26

Voltage terminal 30: 13.6 V
Auxiliary heater: in stages-Enabling for auxiliary heater operation: No enabling
Auxiliary heater: in stages-Act.val.: 1
Auxiliary heater: in stages-Target value: 3
Auxiliary heater: in stages-Specified value for control: 3

1048836 - Blower Output Reduction due to Energy Management
B10CE 00 [00001000] - -
Intermittent - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 6
Fault Frequency: 254
Reset counter: 19
Mileage: 107630 km
Date: 2024.01.01
Time: 01:36:14

Voltage terminal 30: 14.1 V
CAN input signal(s) status-Transport mode: On
CAN input signal(s) status-Static current measuring mode: OFF
CAN input signal(s) status-Windshield wiper: OFF
CAN input signal(s) status-Energy management deactivation stage: Deactivation stage 0
CAN input signal(s) status-Wipe wash: OFF
CAN input signal(s) status-Rear window heater actual value: OFF
CAN input signal(s) status-Back-up lamp: OFF
CAN input signal(s) status-Actual value of windshield heater: OFF

Do either of these indicate problems with the AC pressure sensor or switch ? Thank you so much for your wisdom!

- Rob

 

[Nuje]

Not familiar with that error at all.
Try Googling 1048834 - Functional Limitation due to Energy Management

See what that gets you.

 

[Dannyboy]

Battery level is too low to allow PTC heater to work. Regen needs to power the fans so things like the AUX heater take a back seat until the alternator output is enough to power all requested loads.
It's normal, don't worry. Just go for a good drive and charge up the battery

 

[Robert4604]

Nuje -
Googling that code didn't turn up much useful for me.

Dannyboy -
My new Anti-Gravity battery shows 12.7V after a good drive. Seems good, right?
- Rob

 

[Dannyboy]

Nuje -
Googling that code didn't turn up much useful for me.

Dannyboy -
My new Anti-Gravity battery shows 12.7V after a good drive. Seems good, right?
- Rob

Anti-Gravity battery? You yanking my crank? Or did technology change overnight and I'm the last person to find out?!

On a serious note 12.7 volts is fine.

 

[Robert4604]

Danny -
Anti-gravity are manufacturers, the battery for my TDI weighs 6#, let's just say that's less than the stock lead-acid battery!

 

[ZippyNH]

Danny -
Anti-gravity are manufacturers, the battery for my TDI weighs 6#, let's just say that's less than the stock lead-acid battery!

How do you handle charging when the battery is too cold to accept a charge?! Know you say you keep your car in a garage most of the time...does it have a built in heater to let the cell warm up so it doesn't become damaged?
Might be great for a track car, but one really cold overnight trip....

On another note...these batteries are known for being able to accept a charge VERY quickly, basically taking all your alternator can put out...that's why when similar batteries are used in RVs, vans, motorhomes, etc there is typical a controller that limits maximum input voltage/amps to prevent them from damaging your alternator.... seriously.
The information you are seeing, saying some items are not available is the likely the results of the car seeing a huge amount of power going into the battery, dropping the voltage...so the car is protecting itself.
The 2015 alternator is pretty big and beefy, but kinda $$ to replace. Lead acid batteries are cheaper every 3-5 years.
Just my ¢2
Maybe the BMS has protection to limit inrush current, but it doesn't appear to be true.... similarly I would worry about leaving the car out on a multiple day road trip in the winter. Good luck... somebody will eventually figure it out, but sounds like you are effectively a beta tester.

 

[Robert4604]

Hi, Zippy -
Their Li-ion batteries never need to be charged, just like a lead-acid, the stock alternator does just fine. I haven't noticed any degradation from low temperatures. As you know, after three compressions, my TDI is running.

 

[ZippyNH]

Hi, Zippy -
Their Li-ion batteries never need to be charged, just like a lead-acid, the stock alternator does just fine. I haven't noticed any degradation from low temperatures. As you know, after three compressions, my TDI is running.

Yeah ...the alternator recharges the battery after every start....it is are effectively a sponge for your cars electric system....the biggest issue with that type of battery is they CAN'T charge without damage below 32°f for lithium iron phosphate or a few colder for lithium ion. This has been the BIGGEST reason for the slow/non adoption of the technology outside of motorsports

 

[Robert4604]

Hi, Zippy -
Interesting. I don't see any of this information on the Anti-Gravity Battery site. Maybe they don't want it to get out, but that would be very deceitful, if true. My car was running around here for a few days of -10F, but I'm sure the battery never got that cold, since it lives next to a warm engine.

 

[ZippyNH]

Welcome to the shady world of aftermarket car parts. It's the reason so many people pursue OEM parts