castle911

New to the forum and quite impressed with the knowledge base, so I thought I'd float this one by before digging to deep into it myself.

I recently had my 91' 964 cabrio on consignment and decided to pick the car up due to the dealers inability to get one legit offer after 10 months (...and the car was price right). When I picked up the car they had it running in the back shop, which I'm assuming because they just jumped it. (BTW: the spoiler was in the up position) I turned it off and it started right back up.

On the long drive home I noticed the radio wasn't working, then noticed, the fan blower on the HVAC wasn't working too. After further examination, I discovered the spoiler is non-operable (doesn't go down/up automatically or manually). When I got home I did a quick check on all the fuses and the only one blown was the one for the power mirrors.

Also of note: The car has a good aftermarket battery that is now close to dead after one day of sitting (I know that could be related to the infamous power drain problem which I have had on this car when it sits for a week or more, but never a problem when it was driven daily). I went out and bought a Schumacher 60amp speed charger and the battery will not charge.

So my question is, is there a relay somewhere or something else that could cause all these things to be related and stop working all of sudden? Could this dealership have damaged my electrical system by jump starting attempts, etc. Or should I first replace the battery with a new fresh one and see if there is any change. I'm assuming there will be no change, since the battery did have a charge to start on the drive home and all of these symptoms occur while the car is running.

Any help is appreciated.

-Martin

'91 964 C2 Cabrio - triple black 84K great miles and a beauty (unfortunately for sale)

nekbet

Martin,
I have heard (or read in Adrian's book?) that jumping a really dead car can fry or injure the DME. I've also heard the DME relay sticking on and draining the battery.
If you disconnect the battery and take it to Autozone/etc, they will test it for free. That's the first thing I'd check.

Mike Green
1990 C4 Targa

Colin 90 C2

try wiggling the key. I am troubleshooting a similar problem. I traced it down to a sometimes bad ignition switch. I just ordered one today. I'm hoping that will fix all my problems.

Alan 91 C2

If the dealer let the car sit for a couple of months the battery will discharge totally. Very hard to save a battery treated that way.

Marc Shaw

Whe I got mine from the dealer, they had detailed it for me and had flattened the battery by having the radio while they washed it ( ).

They jumpered it and it restarted but needed a DME reset to run well - I went straight to the P-car mechanic (the car dealer was a Mercedes place) who "Hammered" the car and found/cleared about 14 faults in every system!

Runs like a champ ever since......except for the parts I've broken

Marc

castle911

Thanks all for the quick replies. I'm off to get the battery swapped out tomorrow (still underwarranty for a no questions asked exchange) so hopefully that will do the trick or shed more light on the situation. The DME thing sounds logical, but would it actually effect radio operation? If it were the DME it sounds like there are 2 components. One's the relay DME and the other is the big boy DME. I'm assuming the latter is very expensive to replace? I read in the posts that the DME relay is around $50, which is tolerable.

I'll post what happens after the new battery is in place.

Thanks again.

--Martin

puma1824

Try Sunset Imports or Pelican for the relay should be around $25

castle911

No improvements -- I replaced the battery yesterday with a brand new fully charged battery and I'm still having problems with:
Radio - no power to unit
Fan blower on HVAC - no change in fan speed, but the unit does seem to have power since the A/C button light goes on when pressed.
Rear Spoiler - inoperable both automatically and manually. It's currently in up position.

That's all I've discovered thus far, but otherwise the car runs great.

Any ideas on what this could be? Also, is there an easy way to test the DME brain?

--Martin

'91 964 C2 Cabrio - triple black 84K great miles and a beauty (unfortunately for sale)

GeoffS

Hi

I would check the fuse for the mirrors (again). My electric mirrors blow a fuse which also supplies the fans (but doesn't completely kill the HVAC control unit). In my case the rear wiper then doesn't work, and (I think) the wing fails to move.

One of these may be repeatedly blowing the fuse as you test.

Richard Curtis

Can we assume that when you replaced the battery you cleaned all the connections, including all grounds (or earths for our British friends)? On other German cars I've owned, I've experienced an amazing number of electrical problems due to faulty grounds/earths. Might also be helpful to have the Hammer applied to look for codes.

castle911

GOOD NEWS and MORE BAD....

The Good...Ok thanks to Geoff Shepard who helped me knock out the fan blower issue. It was the fuse again (mirror fuse number 35 I think) and once replaced it seems to be holding and working fine.

Now the BAD... The radio still has no power and the spoiler is still inoperable AND now something NEW.

I decided to go through the fuse and relay bus and checked all the connections, cleaning it out buy pulling and checking each fuse and relay. I also pulled the fuse bus completely out of the house and examined the wires and nothing looked burned up or suspect. Once complete I reconnected the battery and started the car. It started and ran fine, but NOT one gauge was working o the dash: TACH, SPEEDOMETER, OIL GAUGES, FUEL, TEMP, STATUS LIGHTS, etc. were dead. What have I done!?

I've also checked all the grounds and ensured the connections to the battery are clean and tight. All is good in this area.

Any help on any of the above is greatly appreciated. Especially help in getting the radio and spoiler back to normal. I'm assuming the gauge thing is reversible once I understand what I did in the process of qualifying fuse and relay connections.

Answer me this... does the DME have anything to do with the radio and spoiler. If so, is there an easy way to test the DME? I've read so much about of the DME in the forums that it seems like all roads lead to it.

Thanks,

Martin

'91 964 C2 Cabrio - triple black 84K great miles and a beauty (unfortunately for sale)

Colin 90 C2

I just replaced my ignition switch and all my electrical maladies are gone.
My idle is rock steady now and everthing is working as it should.

Before the replacement,I intermittently lost idle, engine blower, hvac fans, headlights, radio and battery drain..

I don't see how the ignition switch could go bad but iI will be doing an autopsy this week.

Roland Shaak

So i popped back on the site cuz I am chasing gremlins (not AMC) SINCE i parked it on a Sunday went to start it two days later - no go (first time (SINCE i changed the DME/FP enable relay) to a 993 part (highly recommended) as preventive caution if you currently run the 964 P/N- I have found many things so I will try to lay them on you somewhat organized. The beast I speak of is 93 RSA that was originally purchased and outfitted to teach a dude to race PCA upper classes. Chipped, cup chassis, half cage two OMPS (well I did take the whiner’s shell out a while back), geared by Johnson and toad hall for Road America and torque courses, RS euro clutch and flywheel, woods light pressure springs, v=blah blah-driven daily for 1 mile beer runs going to Redmond for many years to work (60RT some in freeway miles some in back road miles) and many DE events and it keeps on ticking.

Fans not working, over running for (days), flappers not opening or closing try the CCU first. As an EE I can truly say that the Hella engineers must’a been drinking good stuff or a bean counter was whacking them it sucks from an engineering standpoint.

The power amplifiers used to operate the high current draw stuff like flappers and motors are OVERSTRESSED (IE under rated) and crap out or burn PCB also…PLAUQED by cold solder points my biz pard in Austin has a SMD lab so he took it and microscopically looked at each solder joint (he is a Chrysler man) and stated flipping noise about the multitude of cold joints (in the lingo that mean cracked joints caused by many things but can be an absolute PIA to deal with as a user or as a technician –here is a deadly site
http://www.porschehvac.bergvill.com/ your new best friend.
Remove the noise/aero panel under the engine it can cause many things like burned valves in my case from class F events it can hold heat in freeway or traffic slowdown issue…blah blah
All fuses, relays get deoxit D and deoixt gold…(we used the predecessor at A&M in Hollywood I the 70’s called it tweak then) it kills. Super gamers slather their memory chip contacts with it (I do on my servers)…

http://www.caig.com/ killer stuff, I use it on chips, etc. for electronics
but for the 964 I use 100% deoxit D to clean all the contacts and sockets and fuses (after verifying that they are all the correct amperage rating – then use the correct second coat sometimes Gold sometimes D depends I use all strengths

Then if really in a jiggy mood do all your grounds wit 0000 steel wool or 3Mgreen scrubs soaked with deoxit D 100% (the studs, and the wire terminals- killer improvement in lights etc

Consider new headlight bulbs and or HID assemblies

Move the ABS computer ASAP mine filled with water over the years and gradually rotted neto circuity (5K4 part list mine replacement 500 and clean)…I chose to go to the service manual and put the cup part there on the right inner fender per the SM Carrera RS in white specs in the body manual
Buy the service manuals and Bentley and a few other dedicated books (helpful in many ways)

225’s in front instead of 205 tires

Adjustable downlinks or new suspension is really fun….


The ECU dated my great great grandmother, bulf fired Injectors and other things that scream…piggyback a MoTec M84 cat in Portland has the harness and tuning OR if you are like me….no SMOG laws get a M84 or better and dial in your car with no more dreaded twin distributor failures and sequential injection, individual tuning..blah blah

If going to MoTec or other systems or just using a electromotive ignition unit- go distributor less

The twin distributor has a master and slave set of entities…if the coupling and drive belt fails (it will) nasty stuff can happen, burned valves, holed pistons I ALWYS have the belt changed at service.

MSD 6AL or better twin CDI multispark units; I was a Raytheon missile guy for a while in El Paso they apparently split Raytheon and used modified radar modulator circuitry to create the multi spark..i was there late 70’s and watched demo’s…SO I have used them on every car I have had with tremendous success, and people I recommended them to same same. SAAB, Porsche, VW’s, Mercedes and Jag all benefited
BUT I haven’t on this one because I am going distributor less like I have in the past…no more Achilles heel.

Battery Switch with a fused bypass for Keep alive) CUZ most 964’s seem to have an un-locatable current drain. Perhaps someone can enlighten my dumb self..i pulled all fuses relays and still had a nasty current flow –someday

I have driven mine year round been caught in snow events as in caught…and the car just kept on ticking then I moved from the main to an PNW island and parked it a year….wrong thin g to do by the salt air…so the gremlins have come aboard so…I may do a complete rebuild of it like I have in the past.

No start can also be door light switches (easy to clean and treat) and immobilizer under the pass. Seat (PIA) that thing is affected by damn near everything plus a gas sample from your seat….PIA squared.

Sunroof? Go buy two/four of the (plastic I believe ramps that push the wind deflector down as the sunroof closes here in the PNW (where the sun shines rare)..i have broken three in about 70K miles the sunroof won’t close without you or someone pushing down the defector during g the sudden mountain rain.

Lots of miles on the odometer? Change the ignition switch re-key door locks

Instruments I took my car to Hollywood for a 5 day music bacchanal around the 4th July so it parked in the sun….all of the black is falling from the face of my gauges – I hear it happens

Distributor updates AND rear plastic-OK do the air mod to keep ozone levels down in the distributor to preserve the deadly belt that breaks…HOWEVER be aware;

That the air also dehumidifies all the rear light housing including the center…if the seals fail the mod was worthless no pressure back up the air freely flows out My plastic all of it separated in massive ways
I have new ones to install once I mod the engine and ignition and paint the car (track and road miles have diminished its glow)
Go give the hose a blow job and see if your assemblies are leaking air…for a while I was able to seal mine with silicon in a nice unsightly way…but it got BAAAAD the separation that is

ROD BOLTS…careful…mine have been redone and my RPM limit raised and no problems in 70K+_ miles

If I think of anything else I have encounter I’ll pop back in –thanks for the help I scanned a few pages I think I may have fixed my car

The DME fuse was blown and F34 loose (F.P. fuse I believe) -rollo