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1996 850 Battery Drain Overnight - Yellow Wire Problem

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
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1997 - 2004 C70

PeteB
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by PeteB »

Thanks everyone, will check it out very soon.
PeteB
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by PeteB »

My son stopped by and we were in a rush so I just cut the wire but of course
the check engine light came on. I have to find my scanner to check out the code.
Going to pull the relay next and get a new one.
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abscate
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by abscate »

That will be an SAS code if you didn’t do the delete
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PeteB
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Joined: Tue May 27, 2014 5:50 pm
Year and Model: 1996 Volvo 850 Wagon
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by PeteB »

I did the diode thing a few years ago and it worked with the yellow wire intact but tomorrow I'll see what the code is.
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by PeteB »

OK, we worked on it today and the relay is under the driver's side front fender near the
radiator. It is a large package with 3 connectors. It is obvious from inspection that the connector
toward the rear of the car goes to the SAS fan motor. I reasoned that if the relay is stuck removing
the rear connector is as good as fixing the relay in a car where the SAS is not working.
We measured current to the yellow wire just to confirm the problem, it was high, today it seemed
to measure 2 amps with the ignition off. Pulled the rear plug and it dropped to zero!
We soldered back the yellow wire and started it but still had the check engine light.
Hooked up the scanner, sure enough it was a SAS code, cleared it and it remained cleared.

One lesson here is to simply remove that rear connector if you measure high current on the
yellow wire, or your battery dies overnight and you want to test out this theory.

Our car is missing the engine splash guard and the connectors were filled with water - they face
up and tend to cup water.

Thanks again everyone for the help!
PeteB
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by PeteB »

The car worked fine for over a year and then we got CEL with P0410 SAS code is back.
I clear the code and it comes right back after starting the car.
It seems that the ECU senses the motor being stuck, the diode fix works for that.
But it also seems to sense around the relay if things are working (probably drawing current).
Our car is missing the splash shield so the connections are very corroded, they are black
with tarnish. Cleaned them and it cleared the code but it came back the next day.

I'm going to replace the relay and connectors since I see one on ebay.
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RickHaleParker
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Re: 1996 850 Battery Drain Overnight - Yellow Wire Problem

Post by RickHaleParker »

PeteB wrote: Mon Jul 13, 2020 1:55 pm But it also seems to sense around the relay if things are working (probably drawing current).
P0410 does mean the current draw from the SAS relay is wrong. Could be too high (short) or too low (open). This test cannot detect a defective Air pump. ( If your scanner translation is correct ).

If it is detecting a open circuit such as a burnt out relay coil and you can figure out what the resistance of the relay coil is. A resistor in the relay socket will fool the ECM into thinking the relay is working.

The diode hack tricks the ECM into thinking the O2 sensor reacted to the air pump coming on. That test is a indirect way of checking if the air pump is working.
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