Ignition Mod on F900BT?

[jb79]

Has anybody allready done a mod for the ignition signal?

I mean when you turn the ignition on (without starting the engine) maybe to set up a new target for the navigation and after that you start the engine it will result in a reboot of the F900BT.

 

I've heared about a mod with a diode an electrolytic capacitor to keep the voltage on the ACC input high enough during the engine start to prevent the F900BT from rebooting. But I do't know what capacity would be needed and what current there is on the ACC line.

 

Could somebody give me more information or do I have to test it by myself?

[joegr]

I've done this, but a capacitor is not enough. I had to add a NiCd battery pack. Some transistors were also required. Another member on here has done the same mod and reported that it worked well for them too.

[S4]

Yes, please post more details. I never start my car until fuel pump is done priming so this makes the Avic reboot.

[nkosi]

I've done this, but a capacitor is not enough. I had to add a NiCd battery pack. Some transistors were also required. Another member on here has done the same mod and reported that it worked well for them too.

 

I'm one of those members that Joe shared his solution with, and as Joe said it worked out great for me. Picked up all the parts from Radio Shack.

 

Since it's Joe's solution I'll leave him to post the details.

[jb79]

I just found something that would fit perfectly with some litte modifications:

Switch-Off delay, the 3rd schematic on the page.

 

S1 will be the ignition switch, the radio (ACC in) should be at point A.

Modification 1:

The relais contact KX will be connected to 12V, not to S1.

Modification 2:

The value of C1 is to high. The delay would be 53s with the original value of 0,47µF, that's also the time the radio will play after switching the ignition off. I think 0,047µF will be enough, that should be about 5,3s delay. - Time to start the engine and short enough to switch it off before you leave the car.

[joegr]

The biggest problem with getting the AVIC to continue to run will starting the car is that usually the car battery voltage will fall below 10.5V while doing so. The AVIC will shutdown if the voltage on the red or the yellow wire goes below 10.5 V.

See attached schematic for one solution.

The car_acc_pwr line has to be one that is on when the key is turned to run or start. The ignition power lead would be one example of such a signal.

AVIC.pdf

[dumpystig]

This looks good Joe, I am in the process of trying to find a suitable arrangement to get rid of the bloody PITA re-boots all the time. At the moment I have a switch and relay wired up, but if I forget to press the standby switch on the Avic before leaving or getting back in the car and turning on ignition then I gota suffer the re-boot again

 

Think I will see if your idea will work with a small lead acid battery, I'm assuming the aux battery pack gets charged by the car?

[ubernewb]

if you're not concerned with the power surge that may occur during cranking, why not just change the acc line? instead of using the acc wire in the stock harness, just run a line to the vehicles ignition line? ign remains powered while cranking..

[nkosi]

if you're not concerned with the power surge that may occur during cranking, why not just change the acc line? instead of using the acc wire in the stock harness, just run a line to the vehicles ignition line? ign remains powered while cranking..

 

I tried this myself at one point but found out that the +12V constant also experience a dip during cranking.

[paQ]

I think this is a car-related issue.

My car does not interrupt the battery power during starting. (SAAB)

All functions (headlamps / radio included) continue functioning.

[nkosi]

I think this is a car-related issue.

My car does not interrupt the battery power during starting. (SAAB)

All functions (headlamps / radio included) continue functioning.

 

The starter on my car, and I suspect most cars, causes the battery voltage to dip during the cranking process. The voltage then recovers once the alternator kicks in. It is during this dipping that the voltage falls to an unacceptable level for the HU.

[paQ]

Yes I understand.

Most cars therefor try to not burden the battery by switching off some items. (As headlights)

 

Nevertheless some cars are equiped with some kind of buffer or condensator in order to not have this issue. (as a SAAB 9-5 has)

I see the same thing often with (European) cars fitted with a factory fitted HID lightsystem.

[CatchMeIfYouCan631]

IDK if this has been discussed yet but what about a relay and a diode?

 

85 goes to a ground

86 goes to the vehicle's starter wire

30 goes to a consant 12v source, preferably the constant at the ignition cylinder because it doesn't cut out during start-up.

87a will not be used

87 goes to the constant and ACC of the radio, of course after being diode isolated.

 

-OR-

 

85 groes to ground

86 goes to vehicle's accessory wire

30 goes to ignition constant

87a goes to radio constant and ACC, of course after being diode isolated

87 will not be used.

 

In theory, doing either of these methods should keep the radio powered up when starting the vehicle.

[jb79]

Joe's circuit looks very interesting, but I think the voltage drop caused by a Schottkydiode still is about 0,4-0,5V and that would result in some watts of heat when the F900BT needs some power. I also don't like the idea of having a additional battery located somewhere under the instrument panel. - It can cause a shortage or run out, two things that are not very funny in a car.

 

@paQ: I think a lot of new cars (especially the ones with a CAN BUS or something similar) here in Europe switch off the headlights during the engine start, my Opel Corsa does this too.

 

I think I have to measure the permanent voltage at the F900BT during the engine start, but maybe it is also affected by switching off the power.

[jwq]

Bascally, a starter motor draws 150 - 200 amps cranking the engine.... That's what causes the voltage drop.