When car is first cranked, the RECIRCULATE and ON buttons flash for about 1 minute then stop flashing. All is normal from this point forward. The AC systems work fine. This flashing started a few weeks ago. Any comments on what the flashing means? Thanks Jim

The 20 blinks indicates an error in the ECC. Most likely is the cabin temp sensor is dirty and the miniature fan cannot turn. The sensor is located in the row of switches to the right of the steering column, it has a small grill opening.

You could try using a shop vac to suck dirt out of the grill. Or go the complicated route of pulling out the radio, pulling out the ECC unit, then reaching behind and taking out the sensor to give it a through cleaning. Just be very careful that you do not damage or bend the copper tube.

You could make your own code reader to retrieve the codes and clear them, but once the error is resolved the blinking lights will stay off.
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Keeping it running is better than buying new

Thanks for the info. I'll try cleaning the sensor. What is involved in making a code reader? I have a reader but dosen't read volvo codes.

https://www.matthewsvolvosite.com/forums/viewtopic.php?f=37&t=60660

The above link shows a diagram on the first page. All you need are 3 wires, 3 paper clips, and an LED or 12V light bulb. Instead of port #3, use port #6 for the ECC.

This will work just like the old fashioned OBD I system, a series of blinking lights (3 times) to correspond to the 3 number code.

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Keeping it running is better than buying new

Thanks for the Link. Looks simple enough. I have a dumb question (not knowing what's behind the small grill. Will compressed air work as well as a vacuum?

I would not use compressed air, it might be too strong for the little fan.
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Keeping it running is better than buying new

I'm going to build the simple code reader and try reading the ECC code from the ODB11 plug (pin 6) before I try any repair. What I have read talks to the 850 series but I assume it's the same for a 2000 S70. Please correct me if I am wrong..

I know it works on a 1998.
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Keeping it running is better than buying new

i'm going to try it on a 2000 S70. Will post the results. Thanks Jim

The pin outs (ODBII) for a 2000 S70 appear to be different from the early 850 series. Looks like only 5 pins are wired for contact. Any comments? TKS Jim

http://pinoutguide.com/CarElectronics/volvo_obd_connector_pinout.shtm/

There does not seem to be any differences between 1996 - 2000

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Keeping it running is better than buying new

I did a copy and paste, got the message "page requested not found" Any suggestions?

http://pinoutguide.com/CarElectronics/volvo_obd_connector_pinout.shtml

There was no '/' on the end?

I went to google and searched for pinout guide Volvo
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Keeping it running is better than buying new