Operating the hood, engine on or engine off?

Magicarcher · Post by **Magicarcher** » Sat Jul 22, 2017 7:57 am

Do BMW make any recommendations on whether the hood shut be lowered with the engine running or just ignition on without engine running?

I have had some ECU undervoltage warnings, the car battery charge indicator is fine and the car starts fine so I am wondering if it is operating the car hood without the engine running (which I do quite a lot) is a factor.

Does anyone know how much current the hood motor consumes? I would not have expected it to be that high.

Does anyone else power the hood down without the engine running?

Smartbear · Post by **Smartbear** » Sat Jul 22, 2017 8:07 am

I usually have the engine running when operating the roof, but with a healthy battery it should be fine.
How old is your battery?
Rob

Rusky · Post by **Rusky** » Sat Jul 22, 2017 8:11 am

If you are operating the roof alot off the battery and only doing minimal driving then you are probably going to take out more than you are putting in i would have thought.

tug · Post by **tug** » Sat Jul 22, 2017 8:28 am

Always open and close mine with engine off via Gap Tech. Never had any problems.

Cheers, tug

Magicarcher · Post by **Magicarcher** » Sat Jul 22, 2017 8:32 am

I don't know the pedigree of the battery it was on the car when I bought it. The car cranks with no problems.

I use my z on average 4 days a week and drive approx 50 miles per day, two 45 minute journeys. I never drive the car less than 10 miles, if I have a short journey to make I use my Mini.

The problem I am having is an airbag warning which intermittently comes and the code is "undervoltage"

I am suspicious that the first time it occurred was at work. I had parked up in the morning and on that day accidentally left my cigar lighter accessory (Video Camera) plugged in to the annoying permanently hot cigar lighter. I then put the ignition on and operated my softtop before I started the car. When I drove off I noticed the airbag light had remained on.

Smartbear · Post by **Smartbear** » Sat Jul 22, 2017 8:59 am

It seems zeds can be sensitive to a below par battery & throw up electrical gremlins, yours sounds weakened by the dashcam being left on and then the roof operation didn't help matters, I think most batteries have a manufacture date on them?
Rob

Marlon · Post by **Marlon** » Sat Jul 22, 2017 9:10 am

I usually have the engine running when lowering and raising, however sometimes I lower it from outside - press and hold down the unlock button on the fob (no GapTec or coding required)

Bing · Post by **Bing** » Sat Jul 22, 2017 9:14 am

Magicarcher wrote: ↑Sat Jul 22, 2017 8:32 am ... the annoying permanently hot cigar lighter.

I know that the cig lighter is always live, but are you saying that it's always making the lighter unit hot even when you don't push it in to do so ? If so this could be your problem ? Not sure how you fix it though...

Magicarcher · Post by **Magicarcher** » Sat Jul 22, 2017 9:26 am

Bing wrote: ↑Sat Jul 22, 2017 9:14 am
Magicarcher wrote: ↑Sat Jul 22, 2017 8:32 am ... the annoying permanently hot cigar lighter.
I know that the cig lighter is always live, but are you saying that it's always making the lighter unit hot even when you don't push it in to do so ? If so this could be your problem ? Not sure how you fix it though...

No by permanently hot I means connected to B+ rather than Aux, it does not get physically hot. I do find it a pain to have to remember to unplug it everytime i park!

Ducklakeview · Post by **Ducklakeview** » Sat Jul 22, 2017 9:48 am

The roof motor draws around 9 amps, for the 8 or so seconds it is operating. To be honest, that's probably LESS than the car's systems draw when you first turn the ign on (fuel pumps, ECU and all the other things like heater control flaps and the like that move when the ign gets turned on) SO, unless the battery is pretty weak you shouldn't have a problem.

Mike

Bing · Post by **Bing** » Sat Jul 22, 2017 10:42 am

Magicarcher wrote: ↑Sat Jul 22, 2017 9:26 am
Bing wrote: ↑Sat Jul 22, 2017 9:14 am
Magicarcher wrote: ↑Sat Jul 22, 2017 8:32 am ... the annoying permanently hot cigar lighter.
I know that the cig lighter is always live, but are you saying that it's always making the lighter unit hot even when you don't push it in to do so ? If so this could be your problem ? Not sure how you fix it though...
No by permanently hot I means connected to B+ rather than Aux, it does not get physically hot. I do find it a pain to have to remember to unplug it everytime i park!

Ok, understand now. As others have said, I open and close the hood using my gaptech with the engine off all the time - have done on both my Zs - and it's never had an adverse effect. I also used to have a blackberry and left the charger in the socket all the time and that didn't cause an issue either, even though it was always drawing a little power to light up the LED on the charger itself.

Could it be giving an undervoltage fault because an airbag connector is loose or disconnected ? I know it's unlikely as the connectors are designed not to come loose but you never know. Be a pain trying to find out which one it is though.

Kingfisher · Post by **Kingfisher** » Sat Jul 22, 2017 11:06 am

If all else fails ..... read the handbook! Mine tells me to run the engine while opening and closing the roof so I do ... unless I'm showing off with the fob from out of the car! ...

cj10jeeper · Post by **cj10jeeper** » Sat Jul 22, 2017 12:20 pm

I operated mine remotely for a decade without it ever having issues barely ever with the engine running.
Your ecu is unlikely to be hood related, poor battery perhaps.

buzyg · Post by **buzyg** » Sat Jul 22, 2017 12:21 pm

Never had an issue raising or lowering with the engine off. Not something I have thought about before, but I probably operate about 50/50 engine on engine off.

Magicarcher · Post by **Magicarcher** » Sat Jul 22, 2017 12:54 pm

Given there are a number of people who operate the hood with the ignition off, this is unlikely in itself to cause a problem. The problem will occur if multiple factors cause the terminal voltage at the SIM to fail. The SIM appears voltage sensitive and I found some BMW technical documentation on the web which I annoyingly can't now find, that suggested a supply voltage of below 9V can cause an error to be logged (I can only assume errors are inhibited while the engine cranks because I would expect the system voltage to go below this value when cranking).

I am trying to find the motor in WDS but not getting very far (have found hood module power supplies and switches but not the motor itself). I am assuming it is not grounded itself but the hood module has the ground which is in the right rear quarter well away from the SIM ground at the bottom of the A post/footwell, so a shared ground is unlikely to be the cause.

Ducklakeviews point that there are a good many systems initialising when the ignition is switched on is interesting because if I operate the hood while this is happening and the terminal voltage of the battery is low at the same time, it might be sufficient to cause the voltage to go too low.

I am coming to the conclusion that short of connecting a real time voltage tracer across the SIM I am probably not easily going to find out what is the cause and given it is an intermittent problem even this may not yield conclusive answers.

Z4-forum.com

Z4-forum.com