No power to ECC

dogphife · Post by **dogphife** » 08 Oct 2017, 21:48

Hi everyone! I have a 1998 volvo v70 awd fully loaded with electronic climate control. About 6 months ago my ECC unit stopped working. No lights. No fan. Absolutely just no power. I looked long and hard for a solution. I obviously checked fuses and all of the normal stuff. Even disconnecting the battery ect. Then, I found deep in a forum thread where some guy talked about the door lock trick (I do not have a key fob since I bought the car). He explained it in detail how to do it. I had very strong doubts, but tried it anyway. And it worked the second time I tried! It took about 2 minutes of using his technique for it to work. So then the ECC (Hvac, hence air conditioning lights, fan, heater, everything...) worked perfectly for the last 6 months. Now my girlfriend told me the A/C isn't working. I checked it out and it is the exact some thing. No power. I can't find or remember exactly what the door lock trick was that worked the last time. Any help? So I tried to lock and unlock the doors from the inside with the key in position 2 5 times. nothing. I actually pulled the dashboard ECC out tonight, turned the key on and checked for power coming from the wiring harness on the back. Checked everyone of them and there is no power going to the unit. The fuses are all good. So, I'm thinking that somewhere between the fuse box and the ECC there is a module or something that all of the wires plug into. Where is that? How do I check it? How can I reset it if possible? Help! The door lock trick worked the last time when I had the exact same issue. I would expect it to work again. The HVAC (A/C, blower climate control ect worked perfectly all summer so I know it's good. Help! I have to have a heater for this winter!!!!!!! Thanks

Post by **abscate** » 09 Oct 2017, 06:32

How are you with a volt ohm meter? It's much faster to start diagnose with tests than by symptom.

Scour the web for a wiring diagram for model/year and market so we can point you to where to look for power.

I suspect a fuse or relay has taken out your climate system

dogphife · Post by **dogphife** » 09 Oct 2017, 16:17

I checked the fuses. Like I said, it happened 6+ months ago and I did a door lock trick and it came back on and lasted 6+ months. So it isn't blowing a fuse if I got it to work before. Also, I pulled the plugs out of the back of the ECC and tested them with a volt ohm meter with the key on. I tested every single one and none of them had power. I thought i explained myself? I'm asking where the middle man is. There is obviously something between the fuse box and the ECC. All of those wires in the back are not all going to the fuse box! Where is THAT thing located?

Post by **abscate** » 09 Oct 2017, 17:40

Your experience of 6 months ago may or not be related to present failure. The wiring diagram will answer the question of how power gets to ECC control unit, and tell you where to look. By legal agreement with Volvo we do not host them here, however they are public domain.

Post by **sleddriver** » 10 Oct 2017, 11:37

I've recently noticed in my 98, that the ignition switch occasionally gives me trouble after starting: No radio, dashlights, ECC...if I move the key just a bit, it all lights up. Might work for you....

dogphife · Post by **dogphife** » 11 Oct 2017, 21:15

Thanks guys! I will check it out and post if anything helps. Also, I still can't find the detailed instructions for the door lock trick.

98V70ECC · Post by **98V70ECC** » 22 Sep 2018, 12:41

dogphife wrote: ↑08 Oct 2017, 21:48 Hi everyone! I have a 1998 volvo v70 awd fully loaded with electronic climate control. About 6 months ago my ECC unit stopped working. No lights. No fan. Absolutely just no power. I looked long and hard for a solution. I obviously checked fuses and all of the normal stuff. Even disconnecting the battery ect. Then, I found deep in a forum thread where some guy talked about the door lock trick (I do not have a key fob since I bought the car). He explained it in detail how to do it. I had very strong doubts, but tried it anyway. And it worked the second time I tried! It took about 2 minutes of using his technique for it to work. So then the ECC (Hvac, hence air conditioning lights, fan, heater, everything...) worked perfectly for the last 6 months. Now my girlfriend told me the A/C isn't working. I checked it out and it is the exact some thing. No power. I can't find or remember exactly what the door lock trick was that worked the last time. Any help? So I tried to lock and unlock the doors from the inside with the key in position 2 5 times. nothing. I actually pulled the dashboard ECC out tonight, turned the key on and checked for power coming from the wiring harness on the back. Checked everyone of them and there is no power going to the unit. The fuses are all good. So, I'm thinking that somewhere between the fuse box and the ECC there is a module or something that all of the wires plug into. Where is that? How do I check it? How can I reset it if possible? Help! The door lock trick worked the last time when I had the exact same issue. I would expect it to work again. The HVAC (A/C, blower climate control ect worked perfectly all summer so I know it's good. Help! I have to have a heater for this winter!!!!!!! Thanks

I have the EXACT same problem! Did you ever have any luck?

RonMac · Post by **RonMac** » 29 Aug 2022, 22:21

I too now have EXACTLY the same problem on my S70 1998. Did anyone ever have any luck?
Interestingly, my ECC suddenly has absolutely no power after I washed the engine with a water hose (the day before) while the engine was running and heater fan operating. I wonder if water-entry (e.g. at the Air Cond.) somehow resets something in the ECU and switches off all power supply to ECC? (Although, this may be an association and not an effect)
The working Volvo Scan tool cannot read ECC fault codes (or even communicate with ECC) because the ECC it has no power.
This is a "catch 22" situation. This problem is very serious because the car now cannot be legally registered (for use on roads) without a demister fan.
BTW, I can email anyone original pdf wiring diagrams (ask me at [email protected]).

Post by **abscate** » 30 Aug 2022, 03:48

On the v70 power to the ECC control unit comes direct from the AC relay In the kidney fuse box. It’s pin c5 on my 1999, use the wiring diagram for the 98 to ID the pin and trace back from there.

RonMac · Post by **RonMac** » 05 Sep 2022, 00:57

Thanks abscate

After testing the socket, I found there IS power (12V) at the ECC after all! (Yes, it’s pin C5 on my S70 too.) So, the Fuse No. 35 and relay that feeds it must be providing power okay. But it’s very confusing since "nobody is home" at the ECC. I dismantled the ECC and it looks like new inside. No swollen caps, burnt tracks nor visibly dry solder joints. But,
• No Led lights
• No Blower fan,
• No Control flap movement
• No Temp-sensor fan
Okay. So, where to now.
Another possible clue is an unusual, brief squawk/screech from the engine when starting. (Air Cond Compressor or its belt maybe?) I will next check if the Compressor clutch is locked on. I wonder if I can isolate the power to the compressor to see if everything else comes back on line? If so, then there must be something else telling the climate (Heating cooling) system to stay dead even though its ECC has plenty of power.
It must be something simple to fix while difficult to diagnose.