1998 S70 T5 Another HVAC Problem, flashing ECC lights, No fan (read codes?)

98S70T5 · Post by **98S70T5** » 19 Dec 2019, 10:43

Searched around and didn't see this asked yet so here goes.

My 98 S70 has the automatic dual zone climate control. It works better than any auto control in a vehicle I have ever owned. This has only happened twice but today and a few weeks ago after the car is re started (driven to get fuel or lunch etc). As I recall it was also very cold last time it happened (very low teens here today).

When the car is started some of the lights on the on off/recirculate buttons will flash a few times then there is no blower via auto or manual controls.

Stop and restart the car has fixed it both times. Anyone experienced similar ? I am assuming the brain that controls it is starting to get a little funky.

Thanks,

Klausc · Post by **Klausc** » 19 Dec 2019, 18:27

The blinking lights of death! They signal an error condition within the ECC system. For the 1998 cars, it usually means that the cabin temp sensor has too many dust bunnies blocking the micro fan. The temp sensor is just to the left of the ECC unit and and has a tiny grill opening. Get a vacuum cleaner with a nozzle and try sucking some of the dirt out of it.

Removal of the temp sensor is difficult. Pull out the radio, then pull out the ECC, put the radio back, reach around to the back of the sensor, find the plastic tabs that hold it to the grill, and gently pull. Then clean with a toothpick, gently. Replacement is also difficult, as there is no visibility.

If you elect not to clean, no harm. Just do the temps, vents, and blower speed manually.

98S70T5 · Post by **98S70T5** » 20 Dec 2019, 06:11

It has no manual control when it flashes the error. I will clean that sensor but that doesn't sound like my issue if a sensor malfunction means you still have manual control on the HVAC.

Post by **abscate** » 20 Dec 2019, 06:13

If it resets on a restart it does sound like the ECC control unit, which are cheap from junkyards.

The flashing lights are a sign that an error code is stored, which is a faster path to finding the fault then firing the parts cannon.

98S70T5 · Post by **98S70T5** » 20 Dec 2019, 07:29

Got it, so will the EEC codes read out on a normal OBDII reader? I haven't had to trouble shoot a Volvo auto control HVAC before.

Thanks,

Post by **abscate** » 20 Dec 2019, 07:31

You will need a 'higher end' reader, not just a basic OBD scanner - think 50-100 USD range, not $20.

I think there is a way to get the ECC control unit to flash the codes too; this has been posted here in the P80 Forum

98S70T5 · Post by **98S70T5** » 20 Dec 2019, 11:28

Got it thanks. The ABS was out but magically fixed itself so I need a higher end reader anyhow.

Thanks for the info!

Post by **gmh** » 21 Dec 2019, 12:27

Here's the link to the how to build a flash code reader thread:
viewtopic.php?t=60660
Very useful for reading ECC codes.

Here is my homemade version using the obd1 port salvaged from my 94 850 and an obdII splitter:

: flash code reader.jpg (152.25 KiB) Viewed 2787 times

Post by **jreed** » 22 Dec 2019, 06:23

Once you get the code reader built and working, here is a list of the meanings of the codes:
viewtopic.php?f=1&t=50443&start=20#p380729

98S70T5 · Post by **98S70T5** » 23 Dec 2019, 05:46

Thanks for the info! I have found how it generally only acts up while in AUTO mode on a hot restart (think stopping to get gas). All of the prior offenses it would work properly after a shut down and re start again but this weekend it wouldn't come back unless you had the blower selector in off or manual modes. Then swap back to auto and all was well. I will try and get some codes and see what her major malfunction is.