Did I Kill My Radio?

Did something really stupid. Started out by leaving key in ignition overnight after clearing some DTCs, drained battery to zilch. Hooked battery up to charge it and ran it through a cycle but still no juice. Went to recharge it and saw that I had reversed the poles. First time in my life. Now bear in mind that the key was not on during the charging and it had stopped (although cables still hooked up) before I tried to start the car. I.e., the ignition was not on while the charger was running. After correcting the cables and recharging, it started right up and all seemed normal. Except the radio is dead. I checked the fuses and they are OK and I pulled the head unit out to see if there was a fuse on the back but there isn't. So is this thing beyond help?

Bill, it must be me, but.. It's not clear to me what you did.. 1. Did you recharge the battery with the cables from the car to the battery still connected (correctly) but the charge cables reversed? or 2. Did you recharge the battery with the cables from the charger correctly connected, but the car cables to the battery disconnected? And then connect the cables to the car reversed? or 3. Did you recharge the battery with the cables from the charger reversed on the battery, and car cables to the battery disconnected? And then connect the cables to the car correctly? or 5. Something else? The fact that the ignition key wasn't one doesn't protect the radio. The radio has a constant power connection that is always on (if the fuse hasn't blown) to keep memory for time, radio stations, etc. I seem to recall a fuse on the back of at least some of the audio systems - what system does your Cayman have? I'll just comment - in general - it's best to fully disconnect the battery from the car to charge it, that avoids voltage spikes caused by the sparking when you hook up the charger to the battery. IF you are charging it with the cables to the car still connected to the battery, turn on all the lights and your rear-view window heater. These work as a load on the system damping out the spark caused high-voltage spikes from damaging delicate electronics.

Door No. 1. CD24 Do you know what wires to use to see if I have power to the unit?

Bose ? Non- Bose ? Burmeser? More details make it easier to look this stuff up.

Standard CD24. There are 3 wiring plugs on the back. There is a diagram on Pelican but that is not mine.

After going through about 20 different diagrams from various sources (none of them listed the CD24 but all were the same for this connector) - the radio only has power-on-all-times (aka "Terminal 30") power. It will be on a red wire, usually with a green stripe. One of the smaller connectors - about 12 pins - carries that and the ground (terminal 31) - which is brown/brown. Measure between the two, you should see battery voltage. If you do - it's time to get one of those new fangled "head units" with modern navigation and phone connectivity. If not - check the fuses again. BTW - any smart charger shouldn't have connected if you had the charger cable polarity switched. Old dumb chargers can, and with a dead enough battery actually reverse charge it.. but a modern charger? Surprise to me.. If you were jump starting it from another vehicle's battery - all bets are off. It would be a battle of the batteries (and charging system on the other vehicle.)

Very old, very dumb, clunky shop charger on wheels. This is the underside of plug block. Thanks, Don.

Bill, the two big fat wires are the power wires. The red with a stripe will be 12V+, and brown is always ground on German vehicles. You may be able to back-probe the connector. And the dead battery didn't stand a chance against an old standup battery charger. Those beasts were very poorly regulated, and probably capable of 60A or so. It was probably an impressive spark when the connection was made.

Oops, it is a CDR30! Actually made by Panasonic . When we test the large red/brown and brown we get anomalous readings. Jumps all over sometimes sets at .849.

Key on, key off? Plug in radio, plug out of radio? What you're seeing - the jumping is typical digital meter behavior when it sees no voltage, especially if it's auto-ranging. Sounds as if electricity is getting lost somewhere. From memory that will go to a 15A fuse.

You might take a look at: Cayman - Need CDR30 bluetooth 12-pin plug diagram please Also found: Those aren't my marks - but VBAT and GND are what you want to be measuring..

Just checked an old write-up someone sent me back in 2010 for the pin-outs of the quad-lock connector on a CDR30. I can't attribute it to the original author, but it helped me replace the CDR30 with a Pioneer Z110-BT head unit which is still functioning. Chamber 1 (speaker outputs): 1 HR + (purple) 2 VR + (gray) 3 VL + (white) 4 HL + (green) 5 HR - (purple / black) 6 VR - (gray / black) 7 VL - (white / black) 8 HL - (green / black) Chamber 2 (Electrical): 9 CAN low (blue / black) 10 Telephone mute (?) - Not required 11 CAN high (yellow / blue) 12 Ground (brown) 13 wake up (green) - not required 14 Antenna 12V (white) - to the antenna amplifier in the right A pillar 15 permanent + 12V (red / brown) 16 wake up (?) - Not required Chamber 3 (audio inputs - green): 1 -- 2 Aux L (pink) 3 -- 4 aux screen (black) 5 -- 6 -- 7 Aux R (green) 8 Aux mass (orange) 9 -- 10 -- 11 -- 12 -- Chamber 4 (ext. Amplifier - blue): 4 Car Amp 12V (red / white)

I'm pretty sure we were testing the right wires. Can a dealer check this thing out if I take it to them? If I buy a used one of the exact model no., is it plug and play or is there programming/codes that are needed too?

The used one won't work either if no voltage is getting to it. I think you might want to resolve that before spending the money on a used one.

I talked to a service tech at the dealer and he said that the constant current was very small, like <1v, not 12v. So I tried testing it again w/ the key on, making sure I had good contact on the red/green and brown terminals, and still get the same scrambling display, that does not change when I turn the key off and on. Goes right to 12.25v on the battery. I don't know what else to do.

The service tech is talking out his azz, they often do that to sound expert even when they have no real knowledge of what they're talking about. Lots of mechanics have no idea what they're doing when it comes to electronics. They're good with mechanical things (why they're called "mechanics") but can be absolutely far at sea when it comes to electronics, and if they're not held by the hand troubleshooting with PIWIS they're lost. Service writers are even more limited - since typically they are not mechanics (or electricians or electrical engineers) - instead they're salesmen - advising you how to spend your money maximizing the service you pay the dealership to provide. "Terminal 30" is a DIN standard term that Porsche uses for constant voltage sources . It is not a single "terminal" - it's the designation for any unswitched power source. It isn't right from the battery (although sometimes mistakenly referred to as wired that way) - they ALL go through fuses - and my WAG is you haven't actually tested the fuse that protects this particular circuit (a Terminal 30 circuit.) It's probably labeled something as strange as "PCM2.1" in the fuse panel map. Row A Fuse no. Description Amperage Fuse 1 Power Window Left Door TRM30 30 A Fuse 2 Central Locking Left Door TRM30 15 A Fuse 3 Rear Control Unit TRM30, Rear Spoiler, Rear Lid Release, Two-Tone Horns 15 A Fuse 4 Power Window Right Door TRM30 30 A Fuse 5 Central Locking Right Door TRM30 15 A Fuse 6 Rear Control Unit TRM30, Left Tail Light, Brake Light 15 A Fuse 7 Rear Control Unit TRM30, Right Tail Light, Rear Fog Light 15 A Fuse 8 12V Sockets 7.5 A Fuse 9 Rear Window Heater 25 A Fuse 10 Cigarette Lighter 15 A Row B Fuse 1 Instrument Cluster TRM30, Weight Detection TRM30, Diagnostic Socket TRM30 15 A Fuse 2 Passenger Compartment Sensor 7.5 A Fuse 3 Seat Adjustment Control Unit TRM30, Memory Control Unit, Combination Steering Column Module TRM30, , Tyre Pressure Monitoring Control Unit TRM30, Alarm Siren, Sportchrono, Tilt Sensor 15 A Fuse 4 Headlight Washer system 25 A Fuse 5 Unused 7.5 A Fuse 6 Vehicle Electrical System Control Unit TRM30, Filler Flap Release 7.5 A Fuse 7 Unused A Fuse 8 Tiptronic Control Unit T30 7.5 A Fuse 9 Telephone TRM86S 7.5 A Fuse 10 Heating Klimatronic TRM30 25 A Row C Fuse no. Description Amperage Fuse 1 Unused 7.5 A Fuse 2 Diagnostic Socket TRM15, Klimatronic Control Unit TRM15, PASM Control Unit TRM15, Refrigerant Pressure Sensor TRM15, Clutch Switch, Electronics Box, Mobile Phone TRM15, Heated Spray Jets 7.5 A Fuse 3 Front End Control Unit TRM15, Light Switch TRM15 10 A Fuse 4 Brake Light Switch 10 A Fuse 5 Tiptronic Control Unit TRM15, Tiptronic Position Switch TRM15 15 A Fuse 6 Rear Window Wiper, Non-Dazzle Interior Mirror TRM15, Park Assist Control Unit TRM15 15 A Fuse 7 Combination Steering Column Module TRM15 7.5 A Fuse 8 PSM Control Unit, Sensor Cluster, Key Module TRM15 10 A Fuse 9 PASM Control Unit TRM30 15 A Fuse 10 PSM Control Unit 25 A Row D Fuse no. Description Amperage Fuse 1 Fuel Pump 25 A Fuse 2 Unused 25 A Fuse 3 DME Control Unit TRM30 7.5 A Fuse 4 Unused A Fuse 5 DME Control Unit TRM87, DMTL Valve, Secondary Air Pump Relay, Engine Compartment Fan Relay, Camshaft Adjuster, Camshaft Sensor, Intake Pipe Changeover Valve, Tank Vent Valve, Hot Film Mass Air flow Sensor, Air Conditioner Compressor Relay, Tiptronic Valve, Valve Lift Control 25 A Fuse 6 Oxygen Sensor/Heating ahead of Catalytic Converter, Oxygen Sensor/Heating behind of Catalytic Converter 25 A Fuse 7 Ignition Coils, Injection Valves 15 A Fuse 8 DME Control Unit TRM87 7.5 A Fuse 9 Electronics Box, Mobile Phone TRM30 , DVD Player TRM30 , PCM 2.1 TRM30 , Telephone TRM30 , CD Autochanger TRM30 10 A Fuse 10 ASK Amplifier TRM30, Bose Amplifier TRM30, Bose Subwoofer TRM30, Heating, Climatronic 25 A Row E Fuse no. Description Amperage E1 Seat Adjustment, Left, Seat Memory Motors Left 30 A E2 Seat Adjustment, Right, Seat Memory Motors Right 30 A E3 Unused 30 A E4 Unused A Take note of Row D, fuse #9. If it was me - I'd simply replace it. You can test to see if voltage is getting to the fuse panel on that circuit (from the battery) by removing the fuse, then probing the terminal inputs in the panel (you may want to use an unbent paper clip in the terminals to avoid damaging them.) Test between each terminal and ground. Key on OR off - doesn't matter. One terminal should have 12.6V on it. The other should have basically 0V. If both have no voltage on them - let us know - there could be a large upstream fuse (between the fuse box and battery) that protects multiple circuits.. more study of the wiring diagram would be needed to determine this. I already explained the behavior you're seeing on your digital meter is COMMON on an auto-ranging digital meter. It's noise and nothing but noise. It's not voltage OR current. It means nothing except there is no voltage getting to a point where one would expect to see voltage ALL THE TIME (ignition on or off..) The radio is turned on via a computer signal probably from the main "gateway" in the car (a hub for control circuits.) Current does not equal voltage. Current is measured in AMPS, voltage is measured in VOLTS. The mechanic telling you "constant current was very small, like <1V, not 12V" right away indicates he has no clue. I'd suggest taking it to a good independent garage which has a good reputation for electronics troubleshooting. How do you find one? Ask the PCA members in your area, there will usually be one (if you were in NJ - I use a shop owned by an electrical engineer.) Perhaps you might rethink selling the car in this condition. A reverse polarity connection can bring about unexpected and delayed failures so the new owner may not be really pleased if that happens. NOTE: There are subcategories of "Terminal 30" - I'd suggest viewing: https://en.wikipedia.org/wiki/DIN_72552 - which explains the DIN standard 72552 (used on all Euro cars).. If you're a video-type person - this video explains some of the terminal terminologies as used in a BMW - but the same type of terminals (voltage-sources) exist in your Porsche.

BTW - advice for anyone considering doing their own electronic troubleshooting: For tracing lost voltages - the digital auto-ranging meter really sort of sucks. A simple light probe is often much easier and quicker to use: $2.99* from Harbor Freight. I have one. It works just fine. (*=sometimes given away as a door-prize sort of thing..) I use this in preference to a digital voltmeter. It lights up when it sees voltage. It stays dark when it doesn't. It's binary. The only improvement I can think of would be a buzzer in it. Amazon has one: AWBLIN Automotive Buzzer Test Light, DC 6-24V Dual Color LED Bulb Auto Circuit Tester, Electric Tester Light Tool Probe for Car Vehicle Fuses and Battery Voltage: Amazon.com: Tools & Home Improvement AWBLIN Automotive Buzzer Test Light, DC 6-24V Dual Color LED Bulb Auto Circuit Tester, Electric Tester Light Tool Probe for Car Vehicle Fuses and Battery Voltage: Amazon.com: Tools & Home Improvement www.amazon.com Only issue - it's $14.

Don is knowledgeable and gives good advice - thanks, Don. I gave up and offered my buyer $500 credit and he accepted.