Want to save 10ma?
07-23-2006, 07:16 PM
#1
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Want to save 10ma?
This may be old news, however, I was looking through the Porsche North American service bulletins, and noticed in 1994 Porsche made a change that also affects 1989-1993 964's, which reduces the current draw from the battery by 10ma. To put that in perspective, prior to this change, a 964 should normally draw 26ma to 30ma (engine off for 20 mins, anything electrical turned off, and front trunk latch closed - front hood can be up, just push the latch closed, put tape over it so you remember to open it before closing the front hood). If you have any added devices, the draw may be higher, so reducing 10ma may help your battery retain it's charge a little longer.
For coupes (non-cabriolets...) you need to pull the clock out, and remove bulb number 2, indicated by the arrow:
Put the clock back in, and your done.
For cabs, the process is a little more complicated, involving cutting a wire on the back of the clock and soldering in a new wire. If you want to pursue this, look up service bulletin 9402 (the entire book of 1994 bulletins can be orderd in publication PNA 000 082 E, which runs around $25).
For coupes (non-cabriolets...) you need to pull the clock out, and remove bulb number 2, indicated by the arrow:
Put the clock back in, and your done.
For cabs, the process is a little more complicated, involving cutting a wire on the back of the clock and soldering in a new wire. If you want to pursue this, look up service bulletin 9402 (the entire book of 1994 bulletins can be orderd in publication PNA 000 082 E, which runs around $25).
07-23-2006, 08:46 PM
#3
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Bill,
Please elaborate as to the bulb's original use.
During my recent 'Carrera Clock' project, I noticed quite a few of the used clocks I purchased had white plastic plugs in place of a few bulbs. I wonder if this was Porsche's doing, and the plugs were used to keep as much dust out of the clock housing as possible.
Andreas
Please elaborate as to the bulb's original use.
During my recent 'Carrera Clock' project, I noticed quite a few of the used clocks I purchased had white plastic plugs in place of a few bulbs. I wonder if this was Porsche's doing, and the plugs were used to keep as much dust out of the clock housing as possible.
Andreas
07-23-2006, 10:13 PM
#4
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what is the bulb there for?
Last edited by Bill Gregory; 07-23-2006 at 10:49 PM.
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07-24-2006, 09:19 AM
#8
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Don't worry Dave I was just about to ask the same question And I am supposed to be some sort of Electrical Engineer.
Unless of course our bulbs have a) already been removed or b) lit but we can's see em.
Ps. reading this at work. Your avatar was spotted and got the seal of approval from the lads. Kept them from affecting silly voice and saying"My Names Pesty" for ten seconds
Unless of course our bulbs have a) already been removed or b) lit but we can's see em.
Ps. reading this at work. Your avatar was spotted and got the seal of approval from the lads. Kept them from affecting silly voice and saying"My Names Pesty" for ten seconds
07-24-2006, 11:13 AM
#12
Unfortunately - I only got a printed copy. Although I'm sure my g/f has the originals in electronic format - and although she is happy for me to use her photos as my avatars - I think she might object to me posting them all here at once! Not to mention the fact - that I thought one or two of them were a bit risque for an avatar......
07-24-2006, 11:28 AM
#13
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Originally Posted by DaveK
I would never pretend to be an electrical engineer - which I'm about to prove - but :
How can a bulb draw 10ma unless it's lit?
How can a bulb draw 10ma unless it's lit?
I would also like to know the real scoop on this, but since it isn't needed, it will come out at the first opportunity. When I do it, I will take a before / after reading.
07-24-2006, 11:40 AM
#14
Has anyone verified the current reduction using a meter???????????
The bulb has two sources; the cab top ECU and the central informer ECU.
Without the cab top ECU, the bulb is just an input to the central informer
which could have a 1K ohm pull down resistor to ground; i.e. ~ 10ma.
If the bulb is removed, then the central informer no longer sees a "hi" from
the bulb and thinks there's a cab top fault, i.e. the cab top ECU "pulls" to ground
to turn the bulb "on" which tells the central informer that a fault exists.
That bulb gets #30 ("keep alive") voltage as does the clock when the key is "off".
Bottom line: Bulb should NOT be removed on cab vehicles. For non-cab vehicles,
a central informer fault may exist requiring a reset of the central informer at startup.
The bulb has two sources; the cab top ECU and the central informer ECU.
Without the cab top ECU, the bulb is just an input to the central informer
which could have a 1K ohm pull down resistor to ground; i.e. ~ 10ma.
If the bulb is removed, then the central informer no longer sees a "hi" from
the bulb and thinks there's a cab top fault, i.e. the cab top ECU "pulls" to ground
to turn the bulb "on" which tells the central informer that a fault exists.
That bulb gets #30 ("keep alive") voltage as does the clock when the key is "off".
Bottom line: Bulb should NOT be removed on cab vehicles. For non-cab vehicles,
a central informer fault may exist requiring a reset of the central informer at startup.
Last edited by Lorenfb; 07-24-2006 at 12:08 PM.
07-24-2006, 12:32 PM
#15
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Has anyone verified the current reduction using a meter???????????
Bottom line: Bulb should NOT be removed on cab vehicles.