HU switches off during ignition

Sam Kapasi · 7th July 2007, 11:21

Simply a point of view LBM, there are minor differences in perception and in points of view. Read in detail and you will understand.

We are no longer giving an answer, we're having a discussion in detail. Some of my points and Der Alte's points differ slightly. It's nice to do that. That's all.

low_bass_makker · 7th July 2007, 16:13

Quote:

Originally Posted by Sam Kapasi

Simply a point of view LBM, there are minor differences in perception and in points of view. Read in detail and you will understand.

We are no longer giving an answer, we're having a discussion in detail. Some of my points and Der Alte's points differ slightly. It's nice to do that. That's all.

I thought that all the above discussion were similar..thats all..no problems...

mithun · 10th July 2007, 06:44

Will any damage happens to the electrical system/Music system if I crank the car with the HU ON (in a normal setup w/o any Subs/Amplis) ?

manikjeet · 10th July 2007, 07:04

Quote:

Originally Posted by mithun

Will any damage happens to the electrical system/Music system if I crank the car with the HU ON (in a normal setup w/o any Subs/Amplis) ?

i was told by my installer that its better to switch of the hu before starting the car
it increase the life of the hu

Sam Kapasi · 10th July 2007, 10:57

Quote:

Originally Posted by mithun

Will any damage happens to the electrical system/Music system if I crank the car with the HU ON (in a normal setup w/o any Subs/Amplis) ?

No. That is what this discussion is about. Your car puts off the HU, cranks and then switches it back on, so no harm is done.

tsk1979 · 10th July 2007, 11:56

I don't know if I am right, but I have seen my HU condition at startup tells me whether the battery is charged.
When the OEM battery was about to fail(it was actually an alternator failure) the HU started turning off at startup.
When the alternator got fixed and HU would keep running at startup.
then the Panasonic battery got one cell bad, and thats when the HU started this again. The HU was the indication which prompted me to put a multimeter to the terminals. This time one cell had gone bad.
Then I got Amaron, and HU did not turn off. Again same thing happened, and this time it was an alternator regulator.
Now the HU does not turn off while crank, and I can be sure that the battery is getting charged and is doing fine.

gopinathann · 10th July 2007, 12:00

It is a new feature available in most of the recent models in order to prevent electrical damage to the compnents. In my santro also this happens. Once I gave my bike for a small repair in the night. Once the repair was done the guy told to switch off the head light and start the bike. I asked him why ? He told sometimes the headlight may go off when you start the engine with the head light on. Because of the same reason all the cars disconnect the electrical components during the engine start.

Sam Kapasi · 10th July 2007, 12:20

Tsk, in your case, I can safely assume that your car does not have an auto-cutoff for the HU.
This means that your HU is physically going off when the voltage drops below it's tolerance.

Our previous discussion was regarding cars that actually cut off the accessory supply at the time of cranking. It has nothing to do with the condition of the battery, it is an electrical design. I suspect you don't have this feature in your car.
When your battery is healthy, the voltage stays within the tolerance of the HU and it does not shut off. But I suspect there is still a drop (completely normal)

If I was you, I'd power down the HU before I started my car.

tsk1979 · 10th July 2007, 13:31

Ok, I guess it makes more sense to have HU cutoff and it will prevent damage.
If a car does not have this mechanism, is it possible to have it done while install process. Some king of circuit which will cut off voltage to HU/AMP while crank?

7th July 2007, 11:21	#31
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 2,378 Times View My Garage	Simply a point of view LBM, there are minor differences in perception and in points of view. Read in detail and you will understand. We are no longer giving an answer, we're having a discussion in detail. Some of my points and Der Alte's points differ slightly. It's nice to do that. That's all. Last edited by Sam Kapasi : 7th July 2007 at 11:22.
	() Thanks

10th July 2007, 06:44	#33
mithun BANNED Join Date: Jan 2006 Location: Cochin Posts: 2,195 Thanked: 268 Times	Will any damage happens to the electrical system/Music system if I crank the car with the HU ON (in a normal setup w/o any Subs/Amplis) ?
	() Thanks

10th July 2007, 11:56	#36
tsk1979 Team-BHP Support Join Date: Feb 2005 Location: San Jose, CA Posts: 23,717 Thanked: 22,825 Times View My Garage	I don't know if I am right, but I have seen my HU condition at startup tells me whether the battery is charged. When the OEM battery was about to fail(it was actually an alternator failure) the HU started turning off at startup. When the alternator got fixed and HU would keep running at startup. then the Panasonic battery got one cell bad, and thats when the HU started this again. The HU was the indication which prompted me to put a multimeter to the terminals. This time one cell had gone bad. Then I got Amaron, and HU did not turn off. Again same thing happened, and this time it was an alternator regulator. Now the HU does not turn off while crank, and I can be sure that the battery is getting charged and is doing fine.
	() Thanks

10th July 2007, 12:00	#37
gopinathann BHPian Join Date: Jun 2007 Location: Chennai Posts: 765 Thanked: 20 Times View My Garage	It is a new feature available in most of the recent models in order to prevent electrical damage to the compnents. In my santro also this happens. Once I gave my bike for a small repair in the night. Once the repair was done the guy told to switch off the head light and start the bike. I asked him why ? He told sometimes the headlight may go off when you start the engine with the head light on. Because of the same reason all the cars disconnect the electrical components during the engine start.
	() Thanks

10th July 2007, 12:20	#38
Sam Kapasi Distinguished - BHPian Join Date: Jul 2005 Location: Mumbai (but wat Posts: 6,997 Thanked: 2,378 Times View My Garage	Tsk, in your case, I can safely assume that your car does not have an auto-cutoff for the HU. This means that your HU is physically going off when the voltage drops below it's tolerance. Our previous discussion was regarding cars that actually cut off the accessory supply at the time of cranking. It has nothing to do with the condition of the battery, it is an electrical design. I suspect you don't have this feature in your car. When your battery is healthy, the voltage stays within the tolerance of the HU and it does not shut off. But I suspect there is still a drop (completely normal) If I was you, I'd power down the HU before I started my car.
	() Thanks

10th July 2007, 13:31	#39
tsk1979 Team-BHP Support Join Date: Feb 2005 Location: San Jose, CA Posts: 23,717 Thanked: 22,825 Times View My Garage	Ok, I guess it makes more sense to have HU cutoff and it will prevent damage. If a car does not have this mechanism, is it possible to have it done while install process. Some king of circuit which will cut off voltage to HU/AMP while crank?
	() Thanks