HVAC Problem

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DebbiQ
Posts: 28
Joined: Wed Apr 06, 2005 4:09 pm
Car: 1992 Q45

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I have a 1992 Q with about 125,000 miles and the heating system is malfunctioning. When I start the car the fan blows on high through the defroster vents and there is no display. I can turn the system on and the display will light up and the heat and cool functions seem to work normally, however, the blower is operating at probably the third speed no matter what position it is set for. We did the trouble diagnostic procedure from the manual which indicated a bad sunload sensor. We swapped a presumed good one from a parts car and did not notice any change. It appears the next thing to do is to go to the auto amp harness and run the checks in the manual but we may be getting in over our heads. Do you guys have any thoughts on the matter?


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elwesso
Posts: 34280
Joined: Sun Feb 23, 2003 4:52 pm
Car: 94 Infiniti Q45t 5 spd
2007 BMW M Coupe
2007 Infiniti G35 S 6MT
Location: Indiana
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Behind the glove box there is a resistor thing that often fails, its called the blower amplifier or something like that, and it detects the fan speed..... When it happens the fan is always on full blast....

Part is about $60 new, i have a used one that works (and others do as well, post up a "want to buy" thread in the INFINITI SHOPPING MALL

The sunload sensor will throw a code if its not in the sun!!!

Welcome to NICO!

DebbiQ
Posts: 28
Joined: Wed Apr 06, 2005 4:09 pm
Car: 1992 Q45

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Thanks Wes.I've read about a darlington transistor and fan relay. Can you clarify a little? Still I'm confused by the fact that the fan is on (and blowing thru defroster vents) when the system is supposed to be off. We've got a parts car here, so wouldn't mind doing some parts swapping for diagnosis.

Thx, Debbi

maxnix
Posts: 22628
Joined: Mon Jul 22, 2002 8:11 pm
Car: 1995 Infiniti Q45
1995 Infiniti Q45t
2000 Infiniti Q45

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There is a thread on this with pictures. From your description, I am wondering if your display is out also.

DebbiQ
Posts: 28
Joined: Wed Apr 06, 2005 4:09 pm
Car: 1992 Q45

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The display works when we turn the system on but the fan runs even when the system is off and no display. I have done several searches before even posting and have not seen the thread with pictures. Can you direct me to it?

maxnix
Posts: 22628
Joined: Mon Jul 22, 2002 8:11 pm
Car: 1995 Infiniti Q45
1995 Infiniti Q45t
2000 Infiniti Q45

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elwesso
Posts: 34280
Joined: Sun Feb 23, 2003 4:52 pm
Car: 94 Infiniti Q45t 5 spd
2007 BMW M Coupe
2007 Infiniti G35 S 6MT
Location: Indiana
Contact:

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DebbiQ wrote:Thanks Wes.I've read about a darlington transistor and fan relay. Can you clarify a little? Still I'm confused by the fact that the fan is on (and blowing thru defroster vents) when the system is supposed to be off. We've got a parts car here, so wouldn't mind doing some parts swapping for diagnosis.

Thx, Debbi
The reason is when everything is turned off, it directs some air (as your moving) through the defrost so that the windshield wont fog as easy...

Check those threads that Brian posted and give it a try, and let us know how it wokrs for you!

DebbiQ
Posts: 28
Joined: Wed Apr 06, 2005 4:09 pm
Car: 1992 Q45

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Thanks alot guys. Was indeed a bad fan control amplifier.Debbi

Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

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A bad [failed] fan speed controller is caused by a bad worn out fan motor.The motor will usually take out a new controller if the fan motor is not changed soon!

maxnix
Posts: 22628
Joined: Mon Jul 22, 2002 8:11 pm
Car: 1995 Infiniti Q45
1995 Infiniti Q45t
2000 Infiniti Q45

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And I recall they are about $200 form Joe, and a lot of labor.

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elwesso
Posts: 34280
Joined: Sun Feb 23, 2003 4:52 pm
Car: 94 Infiniti Q45t 5 spd
2007 BMW M Coupe
2007 Infiniti G35 S 6MT
Location: Indiana
Contact:

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The fan motor is easy to do... Took me about 15 mins.....

cjshaw
Posts: 1
Joined: Sat Oct 11, 2008 7:13 am
Car: infiniti q45

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elwesso:Came across a post for fan motor problem you helped solve on a Q in 2005, motor was running full blast and would not shut down. My problem is a fan motor that suddenly won't run, display shows ok but no fan at any speed. Our 1993 Q with about 195,000 has been virtually trouble free! Any suggestions?J&C

Q45tech
Moderator
Posts: 14365
Joined: Tue Apr 30, 2002 3:19 am
Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl

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My first fan motor lasted 10 years and 190k, pulled a used one from a 95Q, it lasted 4 years, pulled another used one and that one is starting to make noise.

The motors and their brushes have a finite life.


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