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Cabin fan runs continuously but no heat or a/c?

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.

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a73s
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Cabin fan runs continuously but no heat or a/c?

Post by a73s » Wed May 18, 2016 8:39 pm

Hi,
I have a Volvo 850T wagon.
Yesterday when I started the engine, the fan in the cabin came on at high speed and doesn't change when I adjust fan speed or temperature. The A/C light stays on when I switch between on and off, and there's no heating or cooling going on.
Is this an ECC problem? Could it be a fuse (or does the fact that the blower is working rule that out?
I don't really have much knowledge of diagnostics, so not sure I can really test it...?

Thanks for any information!

Alan.

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Re: Cabin fan runs continuously but no heat or a/c?

Post by a73s » Wed May 18, 2016 11:28 pm

UPDATE!

Just hopped in the car to do an errand and the fan doesn't work at all now...! Dead, but the lights on the temperature control dials are working....

I looked at the fuses and they are ok, although the #5 fuse area seemed a bit brown as if it had overheated at some point (but the fuse was ok.)

Thanks,
Alan.

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Re: Cabin fan runs continuously but no heat or a/c?

Post by Sommerfeldt » Thu May 19, 2016 4:34 am

Hey Alan.

See if your ECC has set any codes. My first guess would be that you either have a clogged cabin air filter, or it's soaked with water. If your fan isn't working at all, then either the ECC has sensed that there's something wrong and turned the whole thing off (are the tiny lights by your REC and AC switches flashing when you start the car?) or your blower motor is seized. Or both.

The blower motor itself isn't hard to get to. Pull your glove box out (be careful, it gets brittle around the screws), remove the clipped-on wiring harness for the blower etc. and unplug. Remove 4 screws and pull the whole assembly out. If the motor is seized, you can usually get it going by cleaning it and greasing w/ whilte litium grease. Robert DIY on YouTube ("rspi" here) has a couple of great videos on the subject.

Get your codes read and check your cabin air filter first, and then the other stuff after that.

- S
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Re: Cabin fan runs continuously but no heat or a/c?

Post by a73s » Thu May 19, 2016 7:56 am

Sommerfeldt,
Thanks, I'll look at the cabin filter and blower.....may have to take it somewhere to look at the codes.

When I turn on the ignition I DO get the lights at REC and AC flashing for a few seconds...what does that indicate?

Appreciate your help!!

Alan

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Re: Cabin fan runs continuously but no heat or a/c?

Post by abscate » Thu May 19, 2016 8:34 am

That is an indicator there are fault codes in the ECC that can guide you to the faulty parts. You need a decent code reader to access these or the Volvo Software package - see Fora
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Re: Cabin fan runs continuously but no heat or a/c?

Post by erikv11 » Thu May 19, 2016 8:47 am

I would probably get in there, pull the blower motor and see if it is dead or not (apply 12v to it externally). Just to have those data. Other thoughts
- blower motor resistor (but usually this makes the fan run high, else the ECC controls work)
- short to ground somewhere in the wiring (but usually this makes the fan run all the time, even with the key off)
- ECC seems a strong possibility. Can you get your hands on another working ECC? Quickly (briefly) swap yours into another car?
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Re: Cabin fan runs continuously but no heat or a/c?

Post by Sommerfeldt » Thu May 19, 2016 9:50 am

I see that you've got a '95 850 - if you've got the code reader boxes in in the engine compartment, use those to pull your ECC's fault codes and see what it's got to say for itself. In my experience, the ECC's codes are very specific, and will usually tell you all you need to know.

Like erikv11 says, get in there and pull that blower motor - chances are that it needs a little TLC (and grease) in any case. But read your codes out first, so you don't do double work.

- S
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Re: Cabin fan runs continuously but no heat or a/c?

Post by a73s » Thu May 19, 2016 12:11 pm

Thanks for all the replies, really appreciate it!
Sommerfeldt wrote:I see that you've got a '95 850 - if you've got the code reader boxes in in the engine compartment, use those to pull your ECC's fault codes and see what it's got to say for itself. In my experience, the ECC's codes are very specific, and will usually tell you all you need to know.

Like erikv11 says, get in there and pull that blower motor - chances are that it needs a little TLC (and grease) in any case. But read your codes out first, so you don't do double work.

- S
I do have the two code boxes in the engine, and I understand that B1 is the climate control one.... I plugged into that, pressed the button for a second, and nothing happened. I checked that the whole thing was working by plugging into other sockets and I got 1-1-1 from those. Any ideas why would I get nothing at all from the climate control one?


This time (when I went out just now to do the codes) when I turned on the ignition the fan came on, even though it's set to off on the switch. Seems to be blowing well, no squealing etc...? Could it just be the ECC unit?
Thanks again for any suggestions!

Alan

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Re: Cabin fan runs continuously but no heat or a/c?

Post by Sommerfeldt » Thu May 19, 2016 12:17 pm

Hmm... if the two lamps flash on the ECC, that means there are codes stored. The blower shouldn't be running if it's set to Off - are you sure it's not in Auto, instead of Off? It it's indeed Off, then something's definitely amiss.

If there are no codes, you should still get the 1-1-1 from the ECC.

At this point, I would probably check the connections to your diagnostic thingamajigs in the engine compartment, and try cleaning the sockets out of they're dirty. While you do that, disconnect your battery's negative, and leave for 20 minutes. Push the brake pedal once. That should reset some stuff.

- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.

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Re: Cabin fan runs continuously but no heat or a/c?

Post by a73s » Fri May 20, 2016 11:08 am

UPDATE 2
Well, now, even though the ECC unit is set to OFF ('O')...it cycles on and off every 3 or 4 seconds and the fan blows for a second, as soon as I start up the engine, and keeps going (on and off, on and off) the whole time I'm driving. Also it seems to me, that the a/c motor is coming on and off, on and off, at the same time.
I've ordered a used ECC but it won't arrive for a day or two, but now I'm concerned that I may damage the a/c because it seems to be cycling on and off constantly...should I be concerned about that? Any way to disable it for a few days?
I still wasn't able to get any codes to read out from the climate control code reader in the engine (the B1 socket), even though I DO get codes from other sockets in the code reader. I didn't have time to try taking the battery cable off yet but may try that tonight...

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