Battery drain

[RyderMal]

Hi
James Ryder from Malaysia. 964 C2 1990
Have had constant battery drain since purchase + one year. References in a number of forums refer to the drive transistor for the air sampling fan might be the culprit.
Transistor is I believe part of the CCU circuit boards which means a difficult and potentially damaging exercise to the CCU
Is there a way of externally bypassing the transistor or of adding a means of switching off after ignition? Anything rather than have constant battery drain!
Any comments or suggestions welcomed.
James

[inaminit]

James-I cut the power wire to the CCU and taped it. Then I tapped in to the radio power wire, which is nearby, to run the CCU -works fine! Don't forget to document the change in the owner's manual.

[Superkrill]

Open the front fuse box and find the No.1 fuse...that is the CCU Fan fuse.
Just pull it out when you are leaving your car and the fan will stop right away.
Don't forget to put it back in next time you drive though.

[ToreB]

What is the current drain? If it's about 0,5A it's a defective transistor that control the power supply inside the Climate Control Unit.
Replacing the transistor is a no-brainer for a guy with some experience with a soldering iron. I do this repair in 10 minutes.
Here's an explanation on how to do it, see the chapter No CCU fan shutdown.
Cheers,
Tore

[Jim Richards]

I agree with Tore. It's not a bad job for a DiYer.

[RyderMal]

Thanks for all contributors.
ToreB - Do not feel ready to play with CCU at this stage. Cost and problem of replacement if I make a hash of it too horrible to contemplate.
Inaminit - Good idea - may try it if all else fails
Superkrill - Simplest short term answer. Will do.

But of course the simplest answer is to drive the beast every day! That way no battery drain problems. Why did I not think of that earlier!

But again, thanks for yor help.

James

[Esel Mann]

RyderMal,

FWIW, my CCU is suffering from the same issue. The CCU ambient temperature air circulation fan runs. Which, if left running will eventually drain the battery. Early into ownership, I replaced the infamous transistor. Unfortunately that did not remedy the CCU fan problem.

Some other details:

- Every once in a great while, the CCU fan will mysteriously turn off after several minutes (10-20?) once the engine is turned off. This is like a 1 in 50 event. 49 times out of 50 the fan will keep running. Current draw for me is around 550-575mA. Note that my 964 does have an aftermarket alarm/door lock receiver which may have slightly different power requirements than say the factory alarm.

- If I do not plan on driving the next day, I simply disconnect the - cable at the battery. I have noticed most times when I reconnect the - cable at the battery, and I get in the car the CCU fan is not on. Once in a while it will however be on. This is like a 1 in 25 event with the CCU fan on and 24 out of 25 times the CCU fan is not on. This is also before I turn on the engine.


I would not recommend pulling the No. 1 fuse as a long term remedy (however it is certainly fine to do so for fault isolation and maintenance). The reason being, fuse receptacles do have a lifetime with respect to number of fuse inserts/removals. Again nothing to be worried about with the occasional insert/removal. As a long term remedy though there is a possibility of "wearing out" the receptacle. YMMV as wear is statistical in nature. Disconnecting the - battery cable is alternative to the No. 1 fuse.


My near future remedy to this is going to be to pull the CCU and send it out to have it repaired. When I do do so, I can certainly post an update as to the repair house findings and costs if you like.

My current fire is tending to the speedometer. I need the face repaired (back light shines through in a speckle pattern. It's odd as it is the only gauge doing this), and the infamous dissolving trip-ometer gear repaired.

[fleetline51]

I had been dealing with the same anomaly for a year when I finally traced it back to the CCU.My vehicle is a '90 Carrera - C4 Cab. I do not use it often, maybe twice a month for a Sunday drive, so it sits unattended for long periods of time.This is the period in which the battery goes dead due to load drain. Although I haven't completed repair on it as of yet, I did install this Very Heavy Duty Competition grade Cut-Off switch in series with the negative post of the battery and the main ground connection where the negative battery cable used to be . Just before I lock the car, I pop the front lid, then lock it and finally turn the switch to the "OFF' position, close the lid and go have a "Cold One" knowing that my battery will not die over the next "resting" period.

No More dead battery when I want to GO!

Here is a peek of the switch...













Hope this helps!

Best Regards,

Tony

[Hamptonsam]

Any concerns on losing adaptation with battery disconnected? Mine did okay when disconnected with a stock chip, but I noticed that it runs not very well when I lose power with the Steve Wong chip. I complete an adaption with a Bosch Hammer and it is back to normal.

[fleetline51]

Originally Posted by Hamptonsam

Any concerns on losing adaptation with battery disconnected? Mine did okay when disconnected with a stock chip, but I noticed that it runs not very well when I lose power with the Steve Wong chip. I complete an adaption with a Bosch Hammer and it is back to normal.

Yup...Excellent point,Hamptonsam!

My C4 is a bone-stock 3.6 - no comp chip...no problem! If the problem was DEFINITELY traced back to the CCU and only that, then I would install a spst dash mounted toggle switch to the left of the ignition switch and use that to break/make ground connection to the CCU. Just my $.02 ...Other mileage may vary.

Best Regards,

Tony

[Esel Mann]

Originally Posted by Hamptonsam

Any concerns on losing adaptation with battery disconnected? Mine did okay when disconnected with a stock chip, but I noticed that it runs not very well when I lose power with the Steve Wong chip. I complete an adaption with a Bosch Hammer and it is back to normal.

Steve et al. by all means chime in if I am wrong on the following.....

Hamptonsam, the response time of the uC adaptive functions within the ECU is likely dependent upon what initial conditions are utilized for the various variables. The ECU likely has very conservative #'s for variables (on a dead start) seeing as it is designed to recover from all conditions. That is to say the adaptive functions will eventually converge to the point where it is running as you would say (or consider) normal. How quickly it converges is dependent upon run time and those initial settings of the variables. If you disconnect the battery, you in essence have to start at the worst case.

That fact that you are using a hammer could possibly remove some of those worst case conditions. As such the hammer is loading in variables with values which are other than the dead start values which permit the adaptive functions to reduce the response time to the point where it is operating "normally" much more quickly. Also consider that the firmware for the hammer should be expected to be revised over time. So depending upon the revision level of your ECU firmware, or the revision level of the hammer, the hammer may be using more recent initial conditions for the various parameters.

The CCU workarounds are all fine and nice, however in the end, the most prudent solution is to simply pull the CCU and have it repaired. It's not like we are talking about ponying up for a brand new or reconditioned CCU. Consider for a moment: (A) what value do you place on a Porsche that operates like any other car and requires no fancy hoops to jump through when you go to use it? (B) The 964 is only going up in value, should you ever decide to sell in the future, how do you think the selling price will fare between "needs nothing" or "to use it you need to be aware of these hoops to jump through...."

And before it is asked, no, I do not own or have any vested interest in the various Porsche electronics repair shops!

[fleetline51]

Originally Posted by Esel Mann

Steve et al. by all means chime in if I am wrong on the following.....

Hamptonsam, the response time of the uC adaptive functions within the ECU is likely dependent upon what initial conditions are utilized for the various variables. The ECU likely has very conservative #'s for variables (on a dead start) seeing as it is designed to recover from all conditions. That is to say the adaptive functions will eventually converge to the point where it is running as you would say (or consider) normal. How quickly it converges is dependent upon run time and those initial settings of the variables. If you disconnect the battery, you in essence have to start at the worst case.

That fact that you are using a hammer could possibly remove some of those worst case conditions. As such the hammer is loading in variables with values which are other than the dead start values which permit the adaptive functions to reduce the response time to the point where it is operating "normally" much more quickly. Also consider that the firmware for the hammer should be expected to be revised over time. So depending upon the revision level of your ECU firmware, or the revision level of the hammer, the hammer may be using more recent initial conditions for the various parameters.

The CCU workarounds are all fine and nice, however in the end, the most prudent solution is to simply pull the CCU and have it repaired. It's not like we are talking about ponying up for a brand new or reconditioned CCU. Consider for a moment: (A) what value do you place on a Porsche that operates like any other car and requires no fancy hoops to jump through when you go to use it? (B) The 964 is only going up in value, should you ever decide to sell in the future, how do you think the selling price will fare between "needs nothing" or "to use it you need to be aware of these hoops to jump through...."

And before it is asked, no, I do not own or have any vested interest in the various Porsche electronics repair shops!

Esel Mann...

All valid points and well taken, I'm sure , by most of us.

The battery cut-off switch is just one of many means by which a dead battery may be averted due to a possible fault in the CCU circuit...It was never intended as a means to any permanent solution.

It is also ,IMHO, an excellent theft deterrent, provided it is located properly as I believe mine is.

Once again, just my own opinion...Others may disagree.

Best Regards,

Tony

[tasracer]

Check drivers side door switch

It goes bad then the car does not know u oped then closed door and walked away after shut down

[Esel Mann]

Fleetline51,

Please do not be worried about others disagreeing. We are presented here with a nice little gem with this forum (eg. see below!). Tradeoffs usually come into play when going about resolving an issue. What is important to one person may not necessarily be to another. That is why is is so important that any and all ideas or thoughts, and the rational behind them be shared! I hope my posts didn't lead you to think that I was inferring your solution or anyone elses solution is wrong. That was not my intent. My intent was to present an alternative plus my rational behind it. So I hope I didn't piss you off!


Tasracer,

Holy cow! I never knew (nor saw any posts) relating the door switches with something other than the door lights. What you mention though would make sense. As it turns out, my interior ceiling lights are in the permanent off position. I put them in the door control position and sure enough they never turn off! I put them in the third position, the permanent on to verify and sure enough they are permanently on. Heck this might even be associated with the fact that my trunk light for some odd reason also will not turn off when the hood is closed (so I disconnected it). Time for me to try to find wiring diagrams and trace this out. I'll report back with findings once I am able to do so.

[fleetline51]

Originally Posted by Esel Mann

Fleetline51,

Please do not be worried about others disagreeing. We are presented here with a nice little gem with this forum (eg. see below!). Tradeoffs usually come into play when going about resolving an issue. What is important to one person may not necessarily be to another. That is why is is so important that any and all ideas or thoughts, and the rational behind them be shared! I hope my posts didn't lead you to think that I was inferring your solution or anyone elses solution is wrong. That was not my intent. My intent was to present an alternative plus my rational behind it. So I hope I didn't piss you off!


Tasracer,

Holy cow! I never knew (nor saw any posts) relating the door switches with something other than the door lights. What you mention though would make sense. As it turns out, my interior ceiling lights are in the permanent off position. I put them in the door control position and sure enough they never turn off! I put them in the third position, the permanent on to verify and sure enough they are permanently on. Heck this might even be associated with the fact that my trunk light for some odd reason also will not turn off when the hood is closed (so I disconnected it). Time for me to try to find wiring diagrams and trace this out. I'll report back with findings once I am able to do so.

Esel Mann:

Piss ME off? Nah...I been around too long to get pissed off...Heck, I'm so old , I'm lucky if I can even Piss any more without Grunting!

It's all Good, Brother!

All of What you stated is logical and proportionate to this thread...AND well taken.
I know that what I stated and posted would help some others keep from saying "Good Morning" to a dead battery.

That door switch thang IS interesting though...Sumthin' I'm going to have to check out...Maybe when the Spring thaw comes and we warm up a bit!

Joy and Holiday Greetings to You and Your Family!

Best Regards,

Tony

[Esel Mann]

Fleetline51, Thanks! And a safe and enjoyable holidays to you and your family as well!!


About that trunk light.... I confirmed that both door and trunk light switches are properly functioning.

I managed to locate the trunk light switch for '93. It's part of the trunk latching mechanism. You will see the switch on the underside of the trunk latch if the plastic trunk trim piece in the front is removed.

I also see where I erred with respect to thinking something was wrong with the interior and trunk lights. The errors all came about due to a lack of understanding on my part as to how the trunk and interior lighting functions. I did some poking around on some other threads which discussed the trunk and interior lights a bit. Upon running some tests I confirmed the following:

- The trunk light switch does not open (disconnect) until the trunk is FULLY closed. Because of the battery drain, if I don't plan on driving the next day, I pop the trunk, disconnect the battery and simply close the trunk partially (until trunk latch lever clicks) so that when I do go to drive I can easily reconnect the battery prior to hopping in the car. As such even though I had the trunk light electrically disconnected, the switch in essence was still closed (connected) indicating a trunk is open state.

- If the interior lights are put in the door/trunk controlled (center) position, the trunk switch will also control the interior lights. That is to say when the trunk light is on so will be the interior lights.

- Both the interior lights and the trunk lights are on a timer. Once the doors and trunk are completely closed, the lights remain on for approximately 16 seconds whereby then then turn off.


Once I addressed the above, I then determined all is ok with the trunk and door open/closed switches. With the battery reconnected, I simply turned the ignition from off to the on postion and then off again. The CCU fan fired right up (that ****ing CCU fan). I left to do something else for about 25 minutes. I returned and the CCU fan was still on. Taking this another step further I got to thinking if the CCU fan has a dependency on door/trunk open/closed state, perhaps the doors need to be in the locked state too (first test doors were unlocked). I did so and returned about 30+ minutes later. Yep still on.

Good news, I understand how the trunk interior lights work and have ruled that out as a reason the CCU fan is still running. Bad news, the CCU fan is still running...

I do know that my remote central lock system and I presume alarm? was replaced with a Viper setup (found it poking around underneath the radio). I wonder if by chance installation (or perhaps not quite correct installation?) of an aftermarket door lock alarm set up by a PO would cause the CCU fan to run continuously?

[tasracer]

Ok
1 Sit in car with car running
2 turn car off and remove key don't open door
3 like most German cars u should still be able to operate windows... Door sensor know u r still in car
4 windows should operate
5 open and close door
6 windows and/or other electrical should now not operate

If they do... Door switch is bad

[fleetline51]

Originally Posted by tasracer

Ok
1 Sit in car with car running
2 turn car off and remove key don't open door
3 like most German cars u should still be able to operate windows... Door sensor know u r still in car
4 windows should operate
5 open and close door
6 windows and/or other electrical should now not operate

If they do... Door switch is bad

Ok ...I will follow this procedure tomorrow.
Even if what you stated happens, how did you deduce this?

How do We know that what You posted here is Gospel?

Not a "Nay-Sayer"...Let's just say that ,"I'm From Missouri...Show Me!"

Best Regards,

Tony

[tasracer]

How do u think?

It happened to me!

Batt always dead... Car is driven infrequently

Shop found the bad switch

The switch doesn't drain batt
It just leaves the power on so other things can drain it... Like phone charging cord