Volvo 850 ECC Testing/faulty?

Navy · Post by **Navy** » 05 Mar 2020, 12:13

Hello, I know this topic has been well documented but I need some advice/help?
My 1994 Volvo 850 has served me well but sadly 2 months ago the blower failed. The problem started a year earlier where it would sometimes work then only after a restart. DTC 419
So, I wanted to make sure the ECC was sending the correct voltages to the power stage before purchasing another power stage. I am following the ECC service manual and where it says DTC 419 I need to check the voltages between pins 6 and 27...I believe pin 6 is ground.
With the ignition on and the fan speed selector at full (as suggested) I have a reading of 1.5 volts. With the selector moved to (0) off it still shows 1.5 volts then after 3 seconds and what sounds like a stepper motor operating it reads 2.03 volts.
I am unsure if the ECC is faulty or am I missing something. The ECC service manual says if pin 27 reads 1 volt then move on to the next step DTC 418 no signal to power stage.
I was tempted to replace all the capacitors in the ECC but thought I'll check this forum first as someone may have walked this path before.
I know blower motors and power stages should be replaced as a pair but here in London parts are very expensive including second hand parts and it's been cold recently so desperate to save a pound or two.
It's worth mentioning if I ground the blower motor it works.
Many thanks everyone for any guidance.
Andre

Post by **misha** » 05 Mar 2020, 12:42

Remove the blower and lube it with some oil....get a syringe with a small needle and straw from wd-40.You will need that extension to get access to both bearings.
Put few drops too under the cover directly on bearing...under the plastic cover.
After you remove the cover,check brushes.

If they are ok....it should work after lubrication.

Navy · Post by **Navy** » 05 Mar 2020, 13:03

Thanks for replying.
I have already removed the blower motor and cleaned and lubed the bearings with clock oil. The brushes looked ok and the commutator seemed in good condition. I connected the blower to 12vdc and it runs nicely (in my opinion). However, I still get the flashing rec/ac lights on re-assembly.
When I ground/earth the blower in situ it runs fine so I assume no earth from the power stage which in turn may not be getting a signal from the ECC but this is only a guess
Many thanks
Andre.

Post by **scot850** » 05 Mar 2020, 13:11

I am normally 100% with misha on issues, and his suggestion may well work. Blower motors and resistors as you have read are an age related issue with these cars. When the bearing dries out the motors can become intermittent in operation and will overload the blower resistors. Lubing the motor as misha suggested is a good practice anyway.

Motor bearings are also wear prone in a lateral motion. The present themselves with the motor slowing down or speeding up depending on the car is braking or accelerating. If this is the case then the motors days are numbered and replacing it should save the blower resistors being taken out if repaired. In this condition lubing may help for a while but the days are numbered.

I have only once replaced the blower resistor pack and the motor was good.

ECC units do also fail and from what you are saying it sounds that this may be the case in this instance. Try the lube process first and see if it helps and if not then the ECC may be your issue. Also check the 2 cabin sensors hidden behind the grab handles above the front doors. These should be a service item every 10? years or so. They are easily remove once the plastic inner door trim above the door is removed and the grab handle. Clean them with IPA/rubbing alcohol on a few cotton buds to remove all the crap and then you can test them with a 9V battery or re-install and see if they spin up.

If you are still having issues then an ECC unit swap or repair may be the only way forward. If I recall there may be an ECC unit change around 1995 but maybe someone can confirm that. I have an 850 ECC in the garage, but I believe it is later, maybe from a 97, but shipping costs would make it un-realistic. Scrap yards are the way to go but not sure if there are any left in the UK. There may be specialist electrical repair shops that may be able to repair these, or a specialist breaker who guarantees their used parts.

Good Luck,

Neil.

Navy · Post by **Navy** » 05 Mar 2020, 13:37

Many thanks Neil.
I am totally intrigued....I had no idea that the cabin sensors were service items. Ok, I shall check and clean as per your suggestion.
Yes, most breakers in London have been taken over by property developers (makes sense) Only a handful of specialist second hand parts dealers do exist but the are way too far from London for it to make economical sense.
Fingers crossed I make some headway tomorrow.
I have also tried lubing the bearings on the blower motor but it has made no difference as I still have the flashing lights on the ECC.
I will tackle the cabin sensors tomorrow and get back to you.
Thanks again Neil
Andre

Post by **misha** » 05 Mar 2020, 13:40

Does it blow after lubrication even with ac/rec lights are flashing?

Did you reset ECC unit by pulling the fuse for it for a few minutes?

Trying it directly with 12v when it's removed from the car will always work....but not in the car.

That comes from 2 cases....
-1st...blower motor pulls more power than ECC is programmed to and ECC cuts the power to protect itself(possible reasons are that dust is blocking bearings or bearings itself are worn out).
-2nd...power stage is failing.

Cabin sensors will NOT prevent the blower from running.

Navy · Post by **Navy** » 06 Mar 2020, 04:54

Hello, I was just about to pull the cabin sensors and thought I'll check the forum again.

Misha, thanks for replying. In answer to your questions....
With the blower cleaned and lubricated and fitted back into position ignition on it will not work.
With a ground jumper wire connected to the blower plug (blue wire) it works with no key in the ignition.
With the ground jumper wire and ignition on the ECC flashing lights ac/rec the blower works.
With the ground jumper wire and ignition on the ECC ac/rec not flashing the blower works.

I have disconnected the ECC from the 3 green plugs at the rear (makes me feel safer) when I am not using the car and only reconnect it when I am using the car. May I assume this will be the same as pulling the fuse?

I am still wondering why there is only 1.5v at pin 27 (middle plug rear of ECC) when It should be 3v. Cabin sensors perhaps as Neil suggested?
Thanks again
André

Post by **scot850** » 06 Mar 2020, 12:23

Misha and I agree on most things and his knowledge in some areas is way ahead of mine, and I am less familiar with the 850 systems.

Having said that, if the cabin temp sensors cannot sense or have limited capability to do that when their fans are not drawing the air over the temp probes, then the system does not know what temp the car is in and it throws a fault code. I had this happen with a 93 850 we had I had heat only on one side as the sensor was not working. In frustration I pulled both sensors to do a swap over and for the driver's side one was not working. Cleaning it restored the operation to that side.

In your case this may not make a difference, but worth doing anyway to give better temp control when it is working.

Neil.

Navy · Post by **Navy** » 06 Mar 2020, 13:02

Thanks Neil.

I did have time to pull the sensors and was amazed at the dust within. I cleaned both the drivers and passengers side and with the ignition on I can confirm the tiny blades spinning on both sides.
Still no blower but at least that was a job that needed doing so was well worth the effort. Thanks!

André

Post by **misha** » 06 Mar 2020, 16:55

That would leave two possibilities...power stage or ECC itself.