Auto/EEC type. Blower quit working. I was getting the amber flashing lights on the recirculation air and a/c off light. I blew out the dash sensor and that seems to have quit now, but didn't fix the blower not working.
I pulled the motor and it runs great when directly powered with 12V. When I put an ohm meter to the motor connections I found it generally gets 7ish volts and if I slide the blower control to full on it sometimes gets 11.9 volts, but it's intermittent. Seems like it may be a problem with the sliding control switch. Bottom line is that the blower fan seems ok, so I think it's got to be something upstream.
Can the blower fan resistor cause this symptom, or would it more likely be the sliding control switch itself? Or other things to check???
Any help would be appreciated.

 

Usually the resister would cause the fan to only operate in the full on mode. Not sure though, hopefully someone with experience will chime in and help.

 

Think you meant ECC (electronic climate control) or as you say, the "auto" HVAC option.

ECC doesn't have blower resistor pack per se (that's the manual CC) but it does have a "Heater Fan Power Module" up under the rt side of the I/P. That's most likely the issue, but I would do voltage drop tests across it to verify; it supplies the ground portion of the circuit. The pwr module is controlled by the ECC module so it's still possible the ECC module is the issue too.

I'm looking at a '95 850 schematic but should be same or similar on '98 S/V70.

 

I am having the same issue with my fan...namely, it doesn't come on at all. I measured 7 volts. Is that the correct voltage? Is there a way to get direct battery power and ground to test the fan? I also pulled the unit to the left of the fan, the unit with aluminum fins and circuitry...I thought that was the resistor. Any comment helpful and appreciated. I am piggybacking on this post because it seems like the responses may benefit both of us. It would be great to know the outcome of the above recommendations.

 

First off, do you have the ECC or MCC? What MY (model year)?

And where did you measure this 7V? Across the fan motor? At what fan setting? Etc., etc....

 

Thanks for the questions. I have a 1998 S70 Turbo T5. It is ECC according to the owners manual. It has automatic temperature control. THe fan works out of car. On the fan connector in car I now have measured 12v across Yel/Purple connector and 0 on blue.

The resistor unit had no voltage on two wire connector (blue,black) regardless of fan slider position. The 4 pin connector has 12v on Yel/purple and Red/gray connectors. White/Purple and Brown/yellow are zero. No change in voltages with slider position. How does one check the slider? Is it fair to assume the resistor unit is bad?

All measurements made at connector disconnected from fan and resistor circuitry. Should I reconnect everything and try to get new readings?

Thanks for the help.

 

Yep; that's ECC. You need to hook everything up before cking the voltages. And when you say "Red/gray" do you mean gray wire with a red tracer (line) on it? If so, that referred to as gray/red. etc.

BTW: does your ECC have any codes set? You would get blinking lights when you first key ON.

According to schematic I am looking at there are two connectors on the Heater Fan Power Module (aka "resistor circuitry"). All voltages are referenced to ground unless stated otherwise.

Connector 1: has two wires; blk and blue. The blk wire is ground for the system; verify it has 0 ohms resistance to chassis ground. The blu wire feeds the ground side of the blower motor. This blu pin is what you want to measure with everything hooked and key ON; it should go from 12v with fan control off, to 0v with fan control full on. I suspect that latter test will fail; maybe that's where you got the 7V?

Connector 2: has four wires; ylw/brn, violet/wht, gray/red, and red. Yours may be slightly different; let me know if it is. Red is pwr from battery; hot at all times. The other 3 go to the ECC module. Ylw/brn goes to pin B12 of ECC; violet/wht goes to pin A27; gray/red goes to A5 pin.

B12 is a pwm signal from ECC to the Pwr Module; this signal's duty cycle should vary as you move the slider control. Unfortunately that means you'll need a scope to look at it.

A27 is a diagnostic signal back to the ECC; it should read 3v; if it doesn't, there's a problem with the Fan Pwr Module.

A5 supplies pwr (12v) to the Fan Pwr Module.

 

RE: Measuring the pwm signal on pin B12 (or ylw/brn wire on the 4 pin connector): You should be able to approximate the pwm (pulse width modulated) signal duty cycle with a voltmeter since it is a 12v signal. So at 0% duty cycle the voltmeter would read near 0v, 6v would indicate 50% duty cycle, 100% duty cycle would show about 12v, etc.

So the voltage on this ylw/brn pin should vary with the slider control movement. If it does, but the voltage on the blu wire on the 2 pin connector doesn't vary too, then the Heater Fan Power Module is bad.

If the voltage on ylw/brn pin does not change with slider control movement, then you may have a bad ECC, or wiring problem, or maybe a trouble code being set is interrupting this function.

BTW: I would strongly consider getting any HVAC parts like these from the junkyard if you can; new ones from the dealer would be quite expensive I would think.

Please let us know what you find... good luck.

 

Thank you gdog for your detailed instructions. So I went out to the car, put all the components back so I could measure voltages. Turned the key and everything worked. I never got to check voltages since it is, for now, working. I had tested the fan outside the vehicle to be sure it worked. Whether it was stuck (bearing/bushing??) and then became free during the r/r, I have no clue. I guess I will find out in the next week or two if the "fix" is temporary or if I need to run through the voltage checks. If I have to go back in, I will post to this thread what I find.

Thanks again for help with this, the instructions and terminology. Really appreciate it.
jaime