98 S70 ECC only works when hot or after 30 min

[TexasT5]

Good advice, thank you. Have seen posts elsewhere that some 98's could be queried with flash codes; thought that might be too good to be true.

Sounds like I will start with step two in my list above.

[misha]

I'll confirm that tommorow when i check my vol-fcr in s,v70 menu.
But i'm 100% sure that ECC on s,v70 is fully obdII.

[misha]

Yes...ECC is fully OBDII on s,v70('97 & '98).
****'97 EU is '98 U.S.

[TexasT5]

Thank You Misha, Appreciate not wasting any time on fabricating a LED code reader.

Update: I have learned 2 things.

1. Old electronic diagnostic equipment fails. Who would have guessed that my 25 year old Craftsman Multimeter and my 45 year old 12 volt circuit tester would both simultaneously self destruct.? Makes things a bit more difficult but new tools on the way.

2. I studied the wiring diagram in my British version of the Haynes manual. Don't know how I ended up with a British version but that's Ebay for you. It shows power coming from the ignition switch to the Overload Relay X supply. When the relay is energized, it sends 12 V via a yellow/violet wire to the central fuse box and activates fuse 31. Fuse 31 then sends power to the Electronic Climate Control. This same yellow / violet wire also energizes fuse 36 which then sends power to the rear cigar lighter (cigarette lighter for us Americans). So......without any tools.....when I started the car at ambient temp of 66 deg F this morning, the ECC did not come on (as expected) but there was power to both front and rear cigar lighters (tested by plugging my phone charger into each and phone signalled it was receiving charge). So according to my diagram, that would indicate there is power coming from the ignition switch and the relay and my problem is downstream from there.

Next step will be to examine fuse 31 for power on both sides of the fuse with the key on. Fuse 5 appears to send power direct from battery to the ECC and is not switched so that one will also bear diagnosis and inspection.

Will let you know.

[clinton775]

@Texas T5

Ive been having this exact same issue with my '98 v70r. Please keep us informed of what you find! Thank you

[TexasT5]

Update: but not solved.

Got a new circuit tester that has a built in voltmeter via Amazon. Kind of cooler than the old incandescent bulb I've had so many years.

So when I tested yesterday morning, at a cool 71 deg F, and the key on but engine not started; fuse 31 and fuse 5 had battery voltage on both sides but ECC had no power (as expected). Unfortunately, that battery voltage was only 12.1 v at rest and 11.5 v with accessories on. It starts the car fine and reads, 13.4 V with engine running. Doesn't go dead even it sits for a week or more.

Now this ECC problem has been going on for a couple years while my boys drove it, so I assume it was happening even when this battery was good but it throws a variable into my diagnosis.

This morning I hooked up the charger, charged the battery fully, and then started it with the jump start feature engaged trying to ensure it was receiving normal voltage when started. It did not make a difference. It still had no power to ECC on startup, it came on 20 min into my drive, and when I was done with work and the dash registered 100 deg F; it worked fine.

So.....Next I will swap out the battery because, well, it is bad. I imagine I am on the verge of a stranding. I also think to fully trust everything I am testing it should be done at normal voltage. Maybe there will be some benefit of resetting the system as the battery is removed also? ( have done that before after I swapped ECC, twice).

I am suspecting there is a short somewhere between fuse box and plug in the back of ECC, ECC is bad, or maybe the original ECC was bad and I have the wrong junkyard replacement ECC. If good battery fixes this I will be ecstatic.

[misha]

Fully charged battery reads 12.7v.
You will need 14.2-14.4v at battery terminals with engine idling without consumers ON.
WITH consumers ON(headlights,heater blower 1-3 speed and radio) 13.9-14.0v.

Anything below 13.5v with consumers ON is not enough to keep the battery fully charged.

11.9v is discharged battery!
12.2v is 50% of charge.

Battery replacent...i'm pretty sure...will not solve ECC problem,but it will need replacement anyway.
Your B+ cable is probably going out along with fusebox cable going from positive battery terminal.
ECC is probably bad...since they simply go bad....but not in the way you experience it...at least it's not known to us.

Not having the power for a while means it just not getting power,and it's being powered through ignition switch and positive cable which goes from battery terminal to fusebox.

If you have an old laptop with serial DB9 connection and if you can source a VAG-COM KKL cable,i'll be happy to send you a VOL-FCR via email to try to read the codes from your ECC.
But....if there is no power it will not communicate with scan tool,and when it starts working...it works normally.

Power supply for ECC must be checked and it must be powered when key is in pos.I.

ECC can be reset with key in pos.I,where it normally is powered up,with pulling the fuse for ECC for a few minutes and put it back in...repeat few times if necessasary.

If there are faults stored...AC and REC lights will flash everytime you start the car,or when you turn the blower on via slider switch when key is in pos.I.
If they are not flashing...there are no stored codes in ECC.

[TexasT5]

Thanks again Misha,

Sent you a PM with the email. I think running codes is a smart thing to do and really am thankful for your offer. Hope I can still track down a cable via ebay, amazon, or others. I see amazon has VAG-Com KKL cables with a USB interface, but not the serial.
I've seen mixed results on various forms with these cables working or not. Any input from anyone as most of these posts are 5 years old?

I do have a old laptop with windows XP I keep for just these kind of situations when the new computers won't recognize something.

[misha]

Email sent!

[TexasT5]

Just a quick update as have not dedicated much time to this as the darn thing does work when I need it the most, as in afternoons in Texas.

I changed the battery and it made absolutely no difference. I believe this will come as no surprise to anyone.

Got a new multimeter for Father's Day and look forward to interrogating some circuits next time I have a free morning.

Still haven't found a serial port cable. Think I will just order a usb cable and hope I can make it work.

Thanks again to all who have helped.