Hello
I have exactly the same issue with my '96 850T as New2Volvo2 below...

I had to replace the fan in my '93 a few years back but in that case there were obvious
fan noises and intermittent working of different features of the AC and heat. (ECC)
But in this case... everything works fine when it is working... i.e. all fan stages, direction of heat to floor windshield and car itself... fan works from low to high, thermostat works ... everything is normal.
No nasty noises or anything... except the blinking lights of death (recycle and AC)

And then the next time I get in the car there is nothing... no fan or heat until the car warms up and is moving forward then fan-less heat is distributed wherever the dials are set at.
If stuck in traffic I freeze... going along a highway is ok if not TOO cold outside.

The only question I have is that if it is the blower... then why intermittent? How does it work just fine and then nothing? Is it possible that this is an electrical issue or some thermostat, relay or switch not functioning?
IE a blower moter resistor or some such unit?

Before I take out the blower this weekend (in the cold) I would just like to eliminate any other possibilities.

Your experience is welcomed. Thanks guys.

Usually sliding the blower switch to full blast will bypass the resistor. Because the blower is only a few years old, be prepared to replace the resistor. Of course, check the blower connections for a loose wire.

Make your own code reader! I used a 12V line tester which has a little bulb, three large paper clips, spare 18 gauge wire. Instead of a switch, I just touched the wires between #3 and #5 which makes the light glow. Just like the old OBD under the hood. Read all of the codes and write them down before erasing them. I had 16 codes on my 1996 and they were all valid errors.

http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=50443#p251189

If you don't use an LED, the battery will run down lighting up the 12V tester bulb.
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Keeping it running is better than buying new

Thanks Klaus...
I'm a little confused... not unusual mind you.
"Usually sliding the blower switch to full blast will bypass the resistor." When I do this I get nothing... as a matter of fact I have not gotten even a whisper out of the unit in weeks.
I have been moving and super busy... now it's just too cold and widows are fogging etc etc.. need to deal with this.

The fan that I replaced was in a different car so have no idea how old this one is.
But as I said before.... everything was working albeit intermittently ... but when it worked, it ALL worked.
Now there is nothing.... no matter what the settings are at... I have tried them all believe me.
I do get the flashing lights of death as I mentioned on AC and RECY switches

I was just trying to find out if this sounds like a fan motor issue OR a resistor issue?
Is there any easy way to check ?
I have a code reader but the only code I get is for the breather system.

If you were me, where would you start? ... any suggestions are appreciated. Thanks.

Are you running the climate control on manual mode or automatic???

When the resistor fail on the 93/ 850, the fan did not work at any speed.

I got it to work manually by installing a jumper wire with a on/off switch at the hardness. This brings the blower full speed.

The resistor controls the amount of ground that blower receives and does what controls the speed.

I always had problems with the automatic mode and just run it manually.

If you need a resistor, I have one that you can try.

Ok Guys... thanks for the replies...
Here's the plan...
1) I will check for loose wiring at the blower and make sure there is nothing obviously unattached or loose there. And if not...
2) I will build the basic OBD reader as suggested by KlausC... seems like a good thing to have anyway as I get only one reading on my fancy OBD reader and it has nothing to do with the ECC.
If the codes show that I have a blower motor issue... what codes can I expect that would indicate replacement as the best solution?
Also... what codes can I expect if I have a resistor issue? Replacement?

Is the resistor a fairly simple thing to replace? If not, and as they are not cheap, then the suggestion from you hf63 sounds good but can you give me a simple diagram or "how to" explanation... i.e... where is this harness you are talking about? Wire colours etc. Step by step would be appreciated.
If replacement is a consideration and you have a spare (my car is a 96 850 T) what would you need in return for the part? I live in Canada... and it's getting cold!
Are they relatively easy to get from the recycler instead?

Thanks again guys... I appreciate you sharing your knowledge.
Will keep you posted.

With the test probe in #6, you will be able to erase all codes, don't do that! Just go through all of the codes until you get the first one back again, write them all down.

Here are some:

1-5-1 Blower fan switch control signal missing
1-5-2 Blower fan switch control signal short circuit
4-1-1 Blower fan: overcurrent or seized fan
4-1-8 Power unit has no control signal
4-1-9 Power unit giving faulty diagnostic signal

The last 2 are for the rehostat/resister

If you are not familiar with the OBDI code reader, the button is pushed once and the OBD responds by flashing a sequence of 3 numbers for each code found. Pushing the button again after the first code, will produce the next code. Only push the button for a second, no need to hold it down any longer.

If the response is 1-1-1, then no codes are found.

The key must be in posII, so don't forget to turn the ignition off when done reading.

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Yes, you could get a used resistor and hope it works. I know that a 1998 S/V70 has the same one, not sure about 1999 and 2000. There are 2 kinds, one for MCC which is much cheaper but will not work for your car, and one for ECC systems.

The resistor is to the left of the blower, mounted with a T25, directly into the ventilation air stream - think of firewall. Here is a wordy video that shows both resistors, but importantly, where they are. Do check the blower wires for cracks or chafing.

https://www.youtube.com/watch?v=yxSn3vQl0hc

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Keeping it running is better than buying new

Thanks to you both... I will build the code reader and go from there.
I'll let you know how it goes.
Thanks again for your excellent guidance.

Hi Again,



I built a tester and the codes I got from my ECC are these:

124 Driver’s side interior temperature sensor open circuit or shorted to 12 volts
126 Passenger’s side interior temperature sensor open circuit or shorted to 12 volts
417 Passenger’s side interior temperature inlet fan seized
418 No control signal to blower fan power stage

Before I get in there... should I get blower or rheostat... or both?
I will be getting used if possible.
What would you do?

Thanks

So my long sad COLD saga continues... here's the update.

Cleared all codes with home made code reader... thank you Klaus.
Picked up a used resistor from yard and switched it out... got nothing but an added code of 419...
so now have 124. 126, 417, 418 AND 419.
Went back to bone yard and tried another resistor pack which looked almost brand new ... switched it out and got nothing from the fan at any setting. Read codes again and got the 124, 126 and 419.

Frustrating as it was I decided to see if I could get a fan working so got an older fan cage for testing from the guy, tested it at battery and it worked ok... plugged the power line from the resistor into it and the fan worked!!! .... for about 1.5 seconds and then stopped. Turned power on and off and it worked each time but
shut down right away. Then he sourced a newer fan that was working very smoothly at battery test and I tried that.... got nothing again... not even a whisper.
So either I have tried 3 BUM resistors including mine... or it's something else. And yes I have checked the fuses and even swapped them out with others to make absolutely sure it is not fuse related.

I have made arrangements to go back even though it's a cold ride... he is going to fire up one of his parts cars with an ECC and make sure the system is working... and then remove the resistor pack from that car and I'll try that. If anyone has any other way of testing these resistors or can suggest any other relay or switch that may be causing this issue I would really appreciate your input. Thanks for all your help.

Hello to all contributors and 850 owners,

I have been away for a few weeks but owe you all a conclusion to this long exasperating tale. First of all you should know that I have had SUCCESS. As I said before I had swapped out a couple of resistors from the boneyard and tried a couple fans and then swapped out the climate control box... no combination worked. Codes, particularly the 419 code stayed the same.
Back to the boneyard and I asked the owner (nice guy) to find an 850 where the ECC system is working and then I would try to replace the parts one by one... started with the climate control box as mentioned above and no difference...tried that with the (new) system fan... no difference. Then I tried swapping out the resistor ... this was the 4th or 5th one I had tried and everything started up. Hooray... swapped back my own climate control box.. all good... swapped out my own fan ... all good. Conclusion is: as codes, Klaus and others had indicated that it must be the resistor.
But here is the rub... this is where you need to pay attention. I checked the numbers on the back of this particular resistor and they were identical to the original... none of the others matched. It just so happens that this unit came out of another '96 and it worked. The mechanic, who works on nothing but Volvos said that he heard some time ago (and now remembered) that you need to find a resistor with matching numbers. He wasn't sure but thought that may have been a particular quirkiness of the '96 year only but was not sure. Let me tell you that they all look and assemble exactly the same. Now I'm not saying that I know for sure but if ANY of you run into this same issue, and I have heard of people returning resistors, even new or rebuilt ones because they didn't work... START with one that has the same part number as the original. It just may save you a whole lot of grief. Thanks to all contributors and particularly Klaus for insights and code reader build plans etc. I still have 124 and 126 so ECC Auto setting is a little sketchy... but I have HEAT. Thanks to all..

It is time to try another climate control box.

Time to erase the codes, replace the resistor/power stage, and vacuum out the passenger side temp sensor with a crevice nozzle.
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Keeping it running is better than buying new

The part that I bridge was at the hardness where the resistor plugs in. It only has 2 prong plug and I install a jumper wire with the switch. The resistor is next to the blower motor. Shoot me an E-mail @ humbertoflores63@hotmail.com and I can sent you a picture of the jumper. Yes, the resistor is not cheap, and I 2 from cars that I dismantle.

Read this to get the ECC codes:

http://www.matthewsvolvosite.com/forums/viewtopic.php?t=60660

While it is nice, all you really need are a few wires and a bulb (12V 3W, or led bulb). BTW, it is pin #5 and #6 (ECC), not pin #3.

An earlier explanation:

http://www.volvoforums.org.uk/showthread.php?t=46943

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Keeping it running is better than buying new