1994 850 w/blinking AC lights

hart2345 · Post by **hart2345** » 12 Apr 2012, 07:51

I know this information is here, but I have looked until my eyes are bleeding. If someone can provide links it will help much,

Fan does not run, lights flash. This is the auto AC unit
I have:

1. Checked motor and oiled bearings, still not sure it is not drawing too many Amps
2. Cleaned both D and P Temp sensors
3. replaced MOSFET on "resistor pack"
4. checked comp. air is very cold as the outside air coming from vents is cold when comp. is running

I need to know how to check codes and of coarse any suggestions

Does a 1994 come with the box under the hood to check codes? If so how to use.
Do I need a code checker?
Where do I find the meaning of the codes?
and do the codes really help the trouble shooting process?
I am an electronic tech are there schematics or Ohm checks for this unit.

Post by **jblackburn** » 12 Apr 2012, 08:32

Stop guessing!

The car will tell you what's up with it.

One of the advantages of having one of the older models is that you can read ALL codes from the underhood OBDI module.

Here's how:
https://www.matthewsvolvosite.com/read-codes-volvo-850

You want to pull and reset codes from port B2.

hart2345 · Post by **hart2345** » 12 Apr 2012, 12:05

jblackburn,

Thanks you very much. I got 418-no control signal to blower fan power stage, is there any diagram showing the path of this signal?

Post by **Ozark Lee** » 12 Apr 2012, 14:27

It is all in the factory service manual.

https://www.matthewsvolvosite.com/downlo ... vo_850.zip

See the file named AC Heater System Auto.PDF.

What part number did you use to change the MOSFET?

...Lee

hart2345 · Post by **hart2345** » 13 Apr 2012, 11:57

Ozark Lee

Thanks for the down load, I used a IRFP048 I had laying around.
Update, I replaced the power stage, now the fan runs for about 2-3 seconds and shuts down. I get a 419 code, I assume the motor is drawing too much current.

Any sugestion are welcome

Thanks everyone

Post by **Ben850** » 16 Apr 2012, 08:15

Chances are, if the ECC unit is the original, it burnt up. I found that to be the case on my '93. The earlier year ECC had a flaw and evidently they all go bad. If you have the original one, that will most likely be the case. I found a guy on ebay selling them with a guarantee for $100. I have'nt had a problem with it and the codes that showed up after I installed it turned out to be accurate. i.e. passengers side temperature sensor code 126 on the OBD I , B1. After replacing that sensor and resetting the codes, No more blinking lights, and all my fan speeds work again with no new codes.
Good luck.

hart2345 · Post by **hart2345** » 16 Apr 2012, 08:50

Thanks Everyone

This is driving me crazy and it is hot in southeast Texas.

Post by **Ozark Lee** » 16 Apr 2012, 13:16

You can easily check the ECC controller by popping it out of the dash and removing the cover. When they go bad there will be smoke marks on the inside of the cover and a big charred portion of the PC board near the electrolytic caps. I'm not sure of the compatibility of the MOSFET that you used. There was a good thread on Brickboard covering re-building the power stage and part of the writeup detailed how picky the control circuit was about the MOSFET.

http://www.brickboard.com/AWD/volvo/120 ... pdate.html

...Lee

hart2345 · Post by **hart2345** » 16 Apr 2012, 14:38

Thanks Lee

I have removed and checked the ECC controller and see no charred spots, I got a power stage from the salvage yard and now the fan runs for about 2 seconds(did not run at all before). I have order a new fan. The fan does not spin as easy as I think it should.

Post by **jblackburn** » 16 Apr 2012, 19:08

If it finds out the fan is drawing too much current it'll just cut it off before it destroys the resistor (at least theoretically). Sounds like you are taking the right course of action with replacement.