My 88 S4 Auto is at Eurowerks right now getting the TB&WP replaced and they are doing a PPI also. They called me to inform me that the car is drawing .5amps from the battery when the car is off (more than 15 times factory spec). They can trouble shoot it, but that can cost several hunderd dollars just to identify the problem and then more to fix it.

I want to see if I can fix this myself and save a few bucks, but my repair skills are pretty rusty. Worse case scenario, I can allways take it back to them if I can't fix it, but that may ultimately cost more since it would be a "new" job as opposed to a "while you're at it" job.

Do I tell them to go ahead and fix it or is this something that is "simple" that I can try to do myself? Thanks in advance.

 

Maybe simple, maybe not. Lot's of info on this issue here. They should unhook the battery and when you get it back, you start hunting. In the meanwhile, search for "battery drain", it will give you something to read.

 

As Jim B says relay, relay, relay. Pull one at a time and see what happens.

 

Do all your courtesy lights work? (3 position lights in door, roof, trunk) How about the red lights in the door jambs? Mine were corroded and drawing about that amperage.
Noticed in your intro post, your jump point has no cover (<$10) to keep water from dripping on the the hot post, 14 pin connector and passenger coil. I learned from others here that a short bit of hose cut lengthwise and put on the fender seam will also guide water away from the coil areas.
There are some great electrical maintenance threads you should search out here.

 

Thanks all.

All the lights work EXCEPT the courtesy lights. That's what I was leaning towards also - perhaps a bad switch that thinks the doors are always open (?). I will seach the forum for related issues and start trouble shooting

 

If the courtesy lights don't work as designed, the chances are very good that the red lights in the rear edges of the doors are always on.

Getting the lights working correctly is a good first step.

 

While searching this issue, it seems that the best way to check the red lights is to close the door with the windows down and take a peek in where the window goes down (?).

The car is still at EuroWeks, but when I had it I noticed the following...the interior lights on the door work manually, but not automatically, the other 3 roof lights do not work either manually or automatically. In your guys' experience does this sound like it's all part of the same issue or could it be 2 separate issues?

How do I check the door (pin) switches? I read here that I should not pull them out since there is a ground wire that could get ripped out...do they unscrew?

Also, I received the PPI report back that had a few items, I will post a new thread about that. Once again, this newbie needs your help...please.

 

No - better to leave the door open and tape/hold the switch into the closed position.

Quite likely the same issue - debug this first
They unscrew - just hold the center pin still while you unscrew the body - will stop the wire from getting ripped off

Alan

 

Hi Sanjay,

I dont know if this helps.

When I bought my car, '88 928 S4, this past summer, the mechanic who has been servicing the car for the past 5+ years did the TB/WP change for me before I drove it home.

During that work, he showed me a small relay that he had installed on the car, back in the battery box. His explaination to me was that the ECU was drawing power even when the car was off. The purpose of the relay was to disconnect the ECU when the car was off and stop it from draining the battery. Before that the PO had lost a few batteries due to this drain from the ECU.

The PO only put about ~500 miles a year on the car. The relay works fine and unlike the PO, I drive the car daily and the battery charge is fine. I do think it was interesting that a $5 relay would save the battery ($100).

I hope this helps.

VTY,
Joe

 

Joe - I think this is actually a poor band aid for a problem that should be fixed properly... your ECU now has to adapt every time you drive the car... you probanly get lower gas mileage as a result.

Some cars would drive/idle poorly before adaptation was completed...

Hardly a recommended solution in my book

Alan

 

I'd start with the following:

• disconnect ground strap
• hook up ammeter (multimeter in current mode or whatever; an autoranging DVM with at least a 10 A maximum current flow helps to prevent any "overcurrent incidents") between ground strap and grounding point
• make sure not to exceed the maximum current of your ammeter while testing (e.g., if you're using a 1 A range, it's probably not a real good idea to hit the starter... )
• get a feel for normal behavior (i.e., note that there's a significant current flow with interior lights turn on, etc.)
• either disconnect the pin switch for the right-side door, keep it pressed, or remove the fuse for interior lights so you can work around the central electric panel with the right-side door open without turning on the interior lights (of course, if the problem turns out to be in the interior lights circuit, you won't want to have the fuse pulled while inspecting that circuit)
• pull and replace fuses one at a time, checking current flow each time; if you find the magic one that eliminates the drain, now you've isolated the problem circuit and you can concentrate on that one

IIRC, 30 to 40 mA is the normal current flow with stuff working normally.

Some of the usual culprits of parasitic drains have already been mentioned in previous posts. Aftermarket stuff (audio equipment, accessories, etc.) deserves careful attention.

 

This might help also.

https://rennlist.com/forums/928-foru...ir-w-pics.html

When I do these, I unscrew the door switches and cut the wires at the switch connection, disassemble the switch by uncrimping the attachement to the plastic pin, and clean it thoroughly with a dremel wire brush. The reason for this extra trouble is that the contact area within the switchis a recessed taper and its hard to clean right without disassembly.

On the car body, I use a small dremel wire brush, careful not to damage the wire that is still running through that hole. Or you can tie a string to the wire, pull the wire backwards, and let the string hang in the opening while you clean the threaded hole.

Hardest part is uncrimping the remaining wire from the switch (best done in a vice), heat it to remove solder and clean it, then resoldering the wire to the switch while crouching in the doorway of the car.

It is definitely doable --- I've done 8 of them now and they work perfectly.

 

Here is a tool from that may help you find your drain. It was brought up in a thread about a year ago.

http://www.thetoolwarehouse.net/p-11...ties-304b.aspx

 

As you have found, each of the lights in your car effectively has a three-way switch - OFF/ON/AUTO. The first rick is to determine which position is ON and which is AUTO if one of the door switches or the hatch switch is faulty or if there is a short to ground in the brown/white wires.

My first effort would be on the most common cause - the hatch switch. Remove the tool cover and pull the floor carpet back enough to find the switch at the bottom of the hatch lock receptacle. Disconnect the brown/white wire. (Brown is solid ground, brown with a color stripe is a switched ground.)

Your next challenge is that the interior light has a delay built into the system, so that when the doors are closed the lights stay on for a few seconds. Alan's suggestion of taping the switches will at least reduce the complication that this causes in testing. Just be aware that it take some good tape to hold the switches down for an extended time.

Assuming that you have taped the switches down, and several minutes have elapsed, it is easy to see if the red lights are off or on - check both of them. If they are now off, you might have been luck enough to find the problem quickly. Try your interior lights - you should now have two OFF positions and one ON position. Remember the ON switch position. Untape a door switch and see if you now have a second ON position - if so, this is the AUTO position.

Retape that door switch and test the other one in the same way. If it works, congratulations!

If the red lights are still on with the hatch switch disconnected, tape the passenger's door switch. As Alan recommended, hold the pin as you unscrew the switch. You should be able to carefully pull the switch and attached wire out just far enough to check it. Clean the contact area and check the switch operation. If you don't find the problem, check the other switch.

If neither of the three switches seem to be the problem, carefully remove each of the lights and inspect the wiring. You need to study the connections until you understand them. You will have one always-connected power wire (usually red, but green on one light unit)on one end, and one or more brown solid ground wires, and one or more brown/white switched ground wires on the other end. When the switch connects the end of the bulb to the brown wire, the light burns. When the switch connects the end of the bulb to the brown/white wire, the light burns when a door or the hatch is open so the brown/white wire is grounded (and a little longer when the relay grounds it). Look for mixed-up connections or short circuits to ground (pretty rare).

Be very careful with the light over the rear-view mirror - it is very easy for the power wire to short-circuit to the roof metal.

Have fun - at least these aren't nasty and greasy!

 

Thanks all! I may get the car back this evening and I'll start with the switches.

Alan, thanks for the tip on checking the door lights...I guess that was too obvious that I didn't even think about that.