Power Stage Part Numbers Topic is solved

Post by **RickHaleParker** » 08 Dec 2021, 11:00

Navy wrote: ↑08 Dec 2021, 10:07 Not sure if I did something wrong or maybe I should use the ground on the car body???
I have attached a picture which hopefully you can see the two IC's. I think there is something called a Zenner diode down in there too.

Leave the controller disconnected and ground the motor to the chassis ( Body ). You could add the switch and resistance to the ground side. The controller is on the ground side of the motor. The Motor (+) goes straight to a always on fuse.

I figured there might be ICs on the other side. Would of been nice to see the markings.

Zener ... one n. Named after the inventor Clarence Melvin Zener.

Zener diodes are often used to clip voltage spikes like the spikes for a electric motor. Spike them with high enough voltage or often enough and you can send them into permanent breakdown. Another application for a Zener diode is a simple voltage regulator.

Navy · Post by **Navy** » 09 Dec 2021, 10:51

Once again thank you replying.
Also, the infomation on how to connect the blower is a real life saver. I wish I has known this last week.

Would of been nice to see the markings.

Ok,ok with all the help and heat you have afforded me it's the least I can do. Now where's my soldering iron? ah ha!!!
Thanks again....just waiting on delivery
Regards
Andre

Navy · Post by **Navy** » 12 Dec 2021, 10:01

Hello again,
Just following up on the latest developments.
The resistor I ordered arrived yesterday and I fitted it. I switched the ignition on and the blower started spinning for about 2 seconds and then the ECC started flashing the lights and the motor stopped. Everytime I switched ignition off and on the exact same thing happens. Blower runs for 2 seconds and then stops when the lights flash. I increased the blower speed selector to max but it made no difference, the blower runs for 2 seconds probably around 30% power. I decreased the blower speed selector to around 10% and again no difference speed is still approx 30%.
I then removed the blower and double checked it works on the bench and it spins at full speed.
I re oiled the bearings and re installed then wiped the dtc codes.
Ignition on gave the same results no difference.
DTC code is 124 and 419.
Wiped again the codes and got the same two back 124 and 419.
Really not sure where to go from here.
I have disconnected the resistor.
Any suggestions would be really welcome
Regards
Andre

Post by **RickHaleParker** » 12 Dec 2021, 10:39

Check the wiring harness for open circuits, bad connector contacts and shorts to12V.
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1-2-4 Driver's side passenger compartment temperature sensor. Open-circuit or short-circuit to supply

Condition
If signal from passenger compartment temperature sensor is missing or shorted to 12 V, the control unit records the fault and stores the DTC.

Possible source
Open circuit in passenger compartment temperature sensor or wire, or short in wire to 12 V.

Fault symptoms
Fault warning to driver. LEDs by A/C and REC buttons flash for 20 sec.
The control unit substitutes the faulty signal with an estimated value based on the desired temperatures from both temperature switches and the sensor signal from the side which is working. If the sensor signal is faulty on both the driver's and passenger side, the control unit uses the temperature value from that side's temperature switch only.

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4-1-9 Power stage. Faulty diagnostic signal

Condition
If the diagnostic signal from the passenger compartment fan power stage is missing or faulty, the control unit records the fault and stores the DTC.

Possible source
Open circuit in wire across control unit and passenger compartment fan power stage or internal fault in passenger compartment fan power stage.

Fault symptoms
Fault warning to driver. LEDs by A/C and REC buttons flash for 20 sec. Control unit shuts off passenger compartment fan.

Post by **RickHaleParker** » 12 Dec 2021, 10:55

The K1423 is a N-Channel Silicon MOSFET. I have not found out what the AT 346 IC is.

Navy · Post by **Navy** » 12 Dec 2021, 11:14

Many thanks Rick for replying,
Yes, I am totally fed up now as I guess I am back to square one. Faulty resistor or faulty wiring between ecc and resistor. Yes, what are the odds of purchasing a dodgy resistor?
Not sure if I should leave the resistor connected, I have pulled it just in case.
Regards
Andre

Post by **RickHaleParker** » 12 Dec 2021, 11:52

The car is 27 years old. You can expect wiring issues. Disconnect the Power stage and pull the ECC. Probe the harness for shorts and opens. Both of the DTCs can be caused by a short to the 12V. I would be looking for that first.

What condition are the connectors in? They should be shiny. If they are dark it most likely tarnish which is an insulator and will open a circuit. Corrosion will open a circuit. Green stuff is corrosion and it can go down under the insulation where you cannot see it eat a wire in two.

If you just want to keep throwing parts at it, get another wiring harness out of a 1994 - 1997 850 and swap them .. you might get lucky and pick a a harness that is good.

Navy · Post by **Navy** » 13 Dec 2021, 10:50

Thanks Rick, Ok, I shall do as you say and check the wires for shorts and opens. I will also check the connectors and probably take a couple of photos.
I really don't want to change the wiring harness as I am sure the juice is not worth the squeeze.
I will keep you posted.
Thanks again for all your help.
Regards
Andre

Navy · Post by **Navy** » 13 Dec 2021, 12:21

Hello again, I wanted keep eveyone in the loop should I hopefully find the solution. I found this link
http://www.volvotips.com/index.php/850- ... ce-manual/ and plan to follow the testing procedure for the ECC. I will start easily with Rick's suggestion of disconnecting the powerstage and checking the wiring harness first.
Hopefully it will yield some answers.
Kind regards
Andre

Navy · Post by **Navy** » 17 Dec 2021, 10:59

Good evening, I finally had some time to carry the tests as per the Link above.
1. There is good ground circuits following test dtc 121
2. Ecc Pin 6 and 27 have 0 volts (wire may be shorted to ground or open circuit)
3. Checked violet/white wire from resistor to Ecc pin 27 and there is no short to ground or open circuit.
4.Checked voltage between pin 6 and 5 dmm reads 10.98 volts. Suppose to be battery voltage but at least it's not 0 volts.
5. Checked continuity between grey/red wire at resistor and Ecc pin 5 and It reads I have continuity.

I am unsure why it says to use a ohmmeter to test for continuity instead of the audible diode setting. I though the ohmmeter will just check for resistance. Doesn't matter.
Anyway, as I have continuity it suggests replacing the blower resistor. So, I guess I purchased either a faulty resistor or one that is not for my car even though they look the same the pcb is different.
Maybe I should replace the mosfet from my old resistor?
Regards
Andre.

Power Stage Part Numbers Topic is solved

Re: Power Stage Part Numbers