Air pump '98 S70

[MrAl]

Hello there,

I have a 1998 v70 and mine does the same thing and always has since i got the car back some years ago. Is it normal? Well i cant say if it is normal for this make/model/year car in general, but i can say that it is normal for my particular car because i've always seen this behavior since i've had it with some variations as explained below.

It seems to be random though. Sometimes when i get to the first stop sign on my way out somewhere it comes on, sometimes not. Sometimes at a red light it comes on, sometimes not.

If i had to guess, and this is just a guess, it may be checking the system at random times under different conditions, and if it saw a problem at some point it might repeat the test under the same conditions. When i had trouble with my air pump i noticed it came on a lot more after i fixed the problem, but now it is much less.
Then again it could be that it comes on for some other reason because it detected something else that the air pump is used for.

[erikv11]

Thanks MrAl, that is helpful to know.

Can we agree it’s a common occurrence, without the judgemental “ normal” or “abnormal”?

Clearly not unheard of but not enough data to declare it common. ...

The data are there, that is the point of my posts. Dogmatism does not trump empiricism.

I doubt it is related to brown out as common as it is, I think it is part of the routine.

[abscate]

Source code of the ECM with the run conditions are the only way to firmly put the design intent question to bed. Ill bet there as many cars that don't run SAS after start as not; of course, a plethora of variables muddy the water as to why this happens.

Hey, I used a semi-colon!

[erikv11]

Or we could ask jimmy57!

[MrAl]

Thanks MrAl, that is helpful to know.

Can we agree it’s a common occurrence, without the judgemental “ normal” or “abnormal”?

Clearly not unheard of but not enough data to declare it common. ...

The data are there, that is the point of my posts. Dogmatism does not trump empiricism.

I doubt it is related to brown out as common as it is, I think it is part of the routine.

Hi,

That's an interesting point about the brownout, but since i had my new battery i dont see any difference that i can notice. I know there was a difference in battery voltage too with the old battery compared to the new one because i keep an analog meter connected at all times. When i turn the heater on i see the voltage dip and with the old battery it would dip really low but with the new battery it dips only slightly. But through it all the air pump seems to act the same.
I dont have any data on how much the battery voltage dip affects the computer though so all i can do is state my experience with it so far. i have had the new battery for a couple months now.

[RickHaleParker]

MadeInJapan's observations in the other post could be the results of several things.

1. It could be the ECM sending a spurious command.

2. As I stated earlier, it could be the +12V on the coil shorting to another +12V.
The source of this could be right there at the pump relay.
A. Sockets can develop intermittent shorts.
B. Relays can develop internal intermittent shorts.
There is a +12 for the switch pole at the relay.

3. Wiring looms can develop intermittent shorts anywhere along their length.

My '98 C70 SAS does not activate after the initial warm up.

[RickHaleParker]

I dont have any data on how much the battery voltage dip affects the computer

It may not be the voltage level, it could be the slew rate of the fall or rise.
Some digital events are triggered by the Signal edge.

[RickHaleParker]

I would start with tapping on the relay to see if the pump comes on.
Inspect the socket and looms for damage.

[crlande]

That is my game plan, mess with relay and look for vac leaks. Quite the informational topic. Detailed explanation of system function, electrical tech, past posts, philosophy, and punctuation excitement. All from some the heavy hitters on MVS.