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Volvo 850 ECC Testing/faulty?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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jreed
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jreed

Re: Volvo 850 ECC Testing/faulty?

Post by jreed » Sat Mar 07, 2020 6:17 am

I haven't experienced this problem, so I don't have any direct knowledge of how to fix it.

Based on the ECC service manual (available here http://www.volvotips.com/index.php/850- ... ce-manual/ ), since you're getting about 1V between pins 6 and 27, it sounds like you may want go to the diagnostic steps for DTC 4-1-8, set the fan to maximum speed and measure between pins 6 and 42 to see what voltage you're getting. These tests look like they are designed to identify shorts and opens in the wiring.


DTC 4-1-8 NO CONTROL SIGNAL TO ECC POWER STAGE

1) Ensure ignition is off. Connect test unit to ECC control module. Check ground circuits. See DTC 1-2-1, OUTSIDE TEMP. SENSOR CIRCUIT SHORTED TO GROUND. If ground circuits are okay, go to next step.
2) Turn ignition on. Place fan control lever to maximum speed. Connect voltmeter between test unit pins No. 6 and 42. If 6-8 volts are present, go to next step. If voltmeter indicates zero volts, wiring is shorted to ground. If voltmeter indicates 12 volts, wiring
is shorted to voltage. Repair wiring as necessary.
volvo 850 ECC airco climate power stage connectors pins
3) Ensure ignition is off. Disconnect power stage 4-pin connector. See Figs. 14 and 15. Connect an ohmmeter between test unit pin No. 42 and power stage connector terminal 1A. Ohmmeter should indicate continuity. If no continuity is present, check wiring for an open circuit.
1997 855 GLT (Light Pressure Turbo) still going strong. Previous: 1986 240 GL rusted out in '06, 1985 Saab 900T rusted out in '95, 1975 Saab 99 rusted out in '95, 1973 Saab 99 rusted out in '94

Navy
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Re: Volvo 850 ECC Testing/faulty?

Post by Navy » Sat Mar 07, 2020 12:29 pm

Many thanks for replying Jreed.
I agree with you and have just printed all the electrical wiring diagrams for the ecc (with wire colours) and plan to re check the pins. I need to be 100% sure of the voltage readings I'm getting.
I will keep everyone posted.
Thanks again Jreed.
André

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jreed
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jreed

Re: Volvo 850 ECC Testing/faulty?

Post by jreed » Sat Mar 07, 2020 1:37 pm

You're welcome and good luck! Tracking down errors in the ECC system can be laborious. It does seem like a good idea to check the wiring and grounds before testing the components.
For what it's worth, the only part of the system that I've had to replace due to failure was the blower motor. It didn't really fail, but it started to squeak and when I measured its current draw, it was higher than the new motor that I bought to replace it. I tried oiling it a couple of different times, which would quiet it down for a while, but it required repeat treatment. I finally decided to get a new blower motor.
If it's of interest, you can read more about the saga here:
viewtopic.php?t=19322&start=100#p244540
1997 855 GLT (Light Pressure Turbo) still going strong. Previous: 1986 240 GL rusted out in '06, 1985 Saab 900T rusted out in '95, 1975 Saab 99 rusted out in '95, 1973 Saab 99 rusted out in '94

Navy
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Navy

Re: Volvo 850 ECC Testing/faulty?

Post by Navy » Sun Mar 08, 2020 1:37 pm

Thanks again jreed.
While checking the voltages again I noticed a slight play on A connector at the rear of the ECC. After some investigating I think one or more solder joints were loose. I decided to resolder all the pins on A connector and now have a steady voltage reading. I followed the tests for DTC 419 in the ECC service manual and all voltages at pin 6 and 27 and pin 5 and 6 are correct now. The voltages at the 4 pin connector (power stage) are as they should be as well as so I assume wiring is good too.
So, I guess the fault may be either blower motor or more likely power stage. I opened up the power stage and the pcb looks clean no obvious issues. I know very little about mosfets and wondered what voltages I can expect at G D S. I understand this supplies ground to the blower fan but unsure exactly how. Is there a way to test this in situ? If anyone has info on this I would be most grateful or perhaps changed the mosfet with success.
jreed. seems like a good idea for me to check the current draw on my motor too.
Many thanks for eveyones help.
Andre

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jreed
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jreed

Re: Volvo 850 ECC Testing/faulty?

Post by jreed » Sun Mar 08, 2020 2:49 pm

I am far from an expert on MOSFETs and transistor device characterization, but I have played around with measuring the signals on the ECC power stages from Volvo 850's... If it's of use, the write up is here:
viewtopic.php?t=82990
1997 855 GLT (Light Pressure Turbo) still going strong. Previous: 1986 240 GL rusted out in '06, 1985 Saab 900T rusted out in '95, 1975 Saab 99 rusted out in '95, 1973 Saab 99 rusted out in '94

Navy
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Re: Volvo 850 ECC Testing/faulty?

Post by Navy » Mon Mar 09, 2020 6:06 am

Jreed. what a fantastic write up and photos too. I was hoping there was a way to roughly test the mosfet either while connected to the car or removed on the bench with a simple dmm. Otherwise my last option is to replace all the electrolytic capacitors and I suppose I could also replace the mosfet while I'm there too as it's 26 years old.
By the time I get this sorted summer will be here.
Thanks again jreed and well done for documenting the mosfet tests your carried out. Very interesting.
André

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Re: Volvo 850 ECC Testing/faulty?

Post by Navy » Mon Mar 09, 2020 2:11 pm

Good evening. I was just about to start removing the electrolytic capacitors when I noticed something. It appears to me that D4 is somewhat burnt and was hoping for some opinions as if this may be the source of my problems/headache.
Many thanks
Andre
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jreed
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jreed

Re: Volvo 850 ECC Testing/faulty?

Post by jreed » Tue Mar 10, 2020 5:33 am

Yes, D4 and the surface of the board around it do look unusual -- from the pictures it looks like they have overheated and left burn marks. Is it possible to do a diode test on it and see if it still rectifies and what the forward voltage is?
1997 855 GLT (Light Pressure Turbo) still going strong. Previous: 1986 240 GL rusted out in '06, 1985 Saab 900T rusted out in '95, 1975 Saab 99 rusted out in '95, 1973 Saab 99 rusted out in '94

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abscate
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abscate

Re: Volvo 850 ECC Testing/faulty?

Post by abscate » Tue Mar 10, 2020 6:57 am

If we can source and ECC for your from a breakers here (cheap) Im traveling back to UK in May and can post internally.

Do you have a part number on this?

Ill be in Newcastle (Go Magpies) area. Also Bristol and Birmingham areas (my roots)
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Re: Volvo 850 ECC Testing/faulty?

Post by scot850 » Tue Mar 10, 2020 10:24 am

It may not be the diode. If you look at the capacitor above it there looks like it may have leaked to the other side too. Try cleaning the diode with Q-tips and rubbing alcohol (if you can buy any these days due to coronivirus) or IPA (same as rubbing alcohol but higher purity).

You may find that this cleans the component up.

Coming from the way back time of circuit board manufacture, some manufacturers of commercial pcb's were not to careful on cleaning the boards after manufacture leaving fluxes on the surfaces.

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

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