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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.

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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erikv11
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erikv11

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

Post by erikv11 » Fri May 20, 2016 12:04 pm

What if you just unplug the ECC unit? Easy to do, just pull the radio then pop out the ECC. Be careful, there are some sharp edges back there, wear gloves.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

Sommerfeldt
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Sommerfeldt

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

Post by Sommerfeldt » Fri May 20, 2016 4:02 pm

erikv11 wrote:What if you just unplug the ECC unit? Easy to do, just pull the radio then pop out the ECC. Be careful, there are some sharp edges back there, wear gloves.
+1 to that. Sounds like it's definitely your ECC gone rogue. And yeah, wear gloves - I always forget, and end up bleeding from a few knuckles every time I'm back there. :oops:

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

scot850
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Re: Cabin fan runs continuously but no heat or a/c?

Post by scot850 » Fri May 20, 2016 4:31 pm

If I recall there is a tab that needs to be pushed up/down? to release the 850 ECC unit. Gloves for this is a must!

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

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

Post by a73s » Mon May 23, 2016 10:12 pm

UPDATE 3
Well, bad news...go a new (junkyard) ECC and plugged that in...... and nothing. The climate control thing is still dead, no fan, nothing. Tried again to get a code from the diagnostic box in the engine and now when I plug in that probe it just glows solid red......? What could that mean?
I think I'll try to remove the blower motor and see if I can do anything with that.....
Any other suggestions are appreciated!
Thanks,

Alan.

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

Post by scot850 » Mon May 23, 2016 10:57 pm

As you have checked everything else, I'd pull the fan motor and see if there is a lot of movement on the shaft, and if the bearing turns easily.

If the bearings are failing the fan cage can move on the shaft and cause the bearings to lock up. As you accelerate and decelerate, the fan goes on and off.

Resistor pack is another possibility.

Finally, something most over look is to remove the 2 cabin sensors (one behind both grab handles above drivers and passenger seat, and clean them and the little fan motors up from all the junk they suck in over the years. Check if the fans spin up when you re-fit or the sensors are not registering the temperature.

It is strange the test system is not registering faults though.

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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erikv11
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erikv11

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

Post by erikv11 » Mon May 23, 2016 11:51 pm

Wait, in update 2 the fan was on all the time, now in update 3 the fan is never on? When did that change, what happened??

At any rate, inspecting the blower motor was suggested at the outset, it is always the first thing I do because they fail so often in these old cars, check it out for sure.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

a73s
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a73s

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

Post by a73s » Tue May 24, 2016 9:50 am

erikv11 wrote:Wait, in update 2 the fan was on all the time, now in update 3 the fan is never on? When did that change, what happened??

At any rate, inspecting the blower motor was suggested at the outset, it is always the first thing I do because they fail so often in these old cars, check it out for sure.
Erik,
The change just happened for no reason....had a day or so of fan going on and off erratically when it was set to OFF....and now it's completely stopped.
I think I'm going to try to remove the fan and look at that tonight....I was hoping because of the time involved in dismantling everything that the ECC would solve the problem.
Thanks again for your help.
Alan.

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

Post by a73s » Tue May 24, 2016 9:59 am

scot850 wrote: Finally, something most over look is to remove the 2 cabin sensors (one behind both grab handles above drivers and passenger seat, and clean them and the little fan motors up from all the junk they suck in over the years. Check if the fans spin up when you re-fit or the sensors are not registering the temperature.

It is strange the test system is not registering faults though.

Neil.
Neil,
Yes, the diagnostic box is acting strangely (although I have no real experience with this stuff so don't really know what "normal" is!)..first it gave nothing (no light coming on) and now it gives a solid red light, and doesn't respond to any changes when I push in the black button, or hold it down for a few seconds. It IS giving codes for other things in different ports so it doesn't seem to be broken...?

Also, are the 2 cabin sensors small holes in the side of the roof above the grab handles...Do I just pry the plastic piece off and blow out the inside?
Again, thanks for your help (and everyone who's offered advice)!
Alan.

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erikv11
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erikv11

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

Post by erikv11 » Tue May 24, 2016 11:19 am

a73s wrote:...had a day or so of fan going on and off erratically when it was set to OFF....and now it's completely stopped.
I think I'm going to try to remove the fan and look at that tonight....
You will want to check the fuse, maybe it just blew, or maybe the root problem got worse.

This really sounds like a short, like a wire for the fan is frayed and rubbing and shorting intermittently to ground. And I guess it either killed the blower motor, or the wire broke so no fan circuit at all now. So that suggests two tests: (1) can you still run the blower motor if you give it 12V (e.g. take it to the engine bay and use the battery)? If so, the motor is good and you can look elsewhere. If not then you probably have two issues now, including a dead blower motor. (2) Can you ID any bad wiring? When you pull the glove box (I know, it is a hassle ...), try to inspect the wiring that leads to/from the fan.

If, on the other hand, the root problem is somehow the blower motor resistor, you may again find the motor still works. E.g. the unit finally quit altogether (but I think you would expect the fan to work OK on high). I don't know if you can test those power stage/resistor units, worth searching. Alternatively get a junkyard resistor unit and pop it in, see what happens.

Here's a couple good threads:
http://volvospeed.com/vs_forum/topic/14 ... n-for-850/ (excellent post by "Bah")
http://volvoforums.com/forum/volvo-850- ... ere-43632/
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

scot850
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Joined: Mon Apr 05, 2010 2:46 pm
Year and Model: 2000 V70 R
Location: Calgary, Alberta, Canada
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Canada
scot850

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

Post by scot850 » Tue May 24, 2016 11:32 am

erik makes a lot of excellent points. PNP/junkyards are your friends here.

As to your question on the cabin temperature sensors, yes they are the small holes behind the grab handles.

If I recall you have to pull the plastic trim piece over the top of the door, remove the grab handle (I think there is a little flap hiding the screw(s) and then you can access the motor to remove it by making a gap between the headliner and the roof at the door surround.

Removing the motors gives you more access to get into it as you will be amazed at how much junk get sucked into them.

They do fail and/or when clogged up they are not sensing the ECC cannot compute what it needs to do an throws a hissy fit.

The fan is a good place to check as it is the usual suspect now that the youngest 850 is nearly 20 years old. Easy to change. The hardest part is removing the knee brace. There are only 3 nuts holding it in place although it looks like there should be 4. I think there is only 1 on the LH end. It takes some cursing to pull it down and out!

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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