AC fan speed control

[Larry]

I have a '99 RX300, 201K miles. The other day, when the AC reached the set
temperature level, the fan speed reduced, as it is supposed to do. I wanted
a little more air, so I reached over and turned up the fan speed control.
Not the temperature control on the left, but the speed control on the right
side. Well, it went to full speed and stayed there. No matter what I do, it
will not reduce speed from full blast fan. This has been going on for a
couple of weeks now. I have disconnected the battery overnight to drain the
electric system, reconnected it the next morning, and still the same
thing... full speed fan. Any ideas?????

Larry
In the back yard, under the oak.

[Ray O]

Post by Larry
I have a '99 RX300, 201K miles. The other day, when the AC reached the set
temperature level, the fan speed reduced, as it is supposed to do. I wanted
a little more air, so I reached over and turned up the fan speed control.
Not the temperature control on the left, but the speed control on the right
side. Well, it went to full speed and stayed there. No matter what I do, it
will not reduce speed from full blast fan. This has been going on for a
couple of weeks now. I have disconnected the battery overnight to drain the
electric system, reconnected it the next morning, and still the same
thing... full speed fan. Any ideas?????
Larry
In the back yard, under the oak.

Does your climate control show the fan speed, and if so, does it show a low
fan speed even though the fan is running on high? If that is the case,
check the resistors by the blower cage. One or more may be bad.

[Larry]

"..... does it show a low
fan speed even though the fan is running on high?..... "

Yes it does. The climate control shows the fan speed dropping down (fewer,
shorter bars) but the fan still continues to run on high speed. Where can I
find some detailed information about components and schematics? My Haynes
manuel has the standard " Installation Is The Reverse Of Removal"
directions, with no details at all.

Larry
In the back yard, under the oak.

[Ray O]

Post by Larry
"..... does it show a low
fan speed even though the fan is running on high?..... "
Yes it does. The climate control shows the fan speed dropping down (fewer,
shorter bars) but the fan still continues to run on high speed. Where can I
find some detailed information about components and schematics? My Haynes
manuel has the standard " Installation Is The Reverse Of Removal"
directions, with no details at all.
Larry
In the back yard, under the oak.

If the climate control shows the fan speed dropping but the fan continues to
run on high, then I would check the blower resistors. The only place I am
aware of with detailed information is the factory service manual, but
diagnosis should not be too difficult with a volt/ohm meter. The resistor
pack or frame is usually located in the air flow from the blower so that the
air cools the resistors. The resistors turn the electricity into heat and
the air from the blower gets rid of the heat. The reduced current going to
the blower motor reduces the motor speed. If the resistors don't resist,
then full power goes to the blower motor.

The blower motor is usually located under the passenger side of the
dashboard, and removing the shroud around the blower should provide access
to the resistor pack.

[Jay Somerset]

On Mon, 4 Jun 2007 11:15:51 -0500, "Ray O"

Post by Ray O

Post by Larry
"..... does it show a low
fan speed even though the fan is running on high?..... "
Yes it does. The climate control shows the fan speed dropping down (fewer,
shorter bars) but the fan still continues to run on high speed. Where can I
find some detailed information about components and schematics? My Haynes
manuel has the standard " Installation Is The Reverse Of Removal"
directions, with no details at all.
Larry
In the back yard, under the oak.

If the climate control shows the fan speed dropping but the fan continues to
run on high, then I would check the blower resistors. The only place I am
aware of with detailed information is the factory service manual, but
diagnosis should not be too difficult with a volt/ohm meter. The resistor
pack or frame is usually located in the air flow from the blower so that the
air cools the resistors. The resistors turn the electricity into heat and
the air from the blower gets rid of the heat. The reduced current going to
the blower motor reduces the motor speed. If the resistors don't resist,
then full power goes to the blower motor.
The blower motor is usually located under the passenger side of the
dashboard, and removing the shroud around the blower should provide access
to the resistor pack.

All of the resistors would have to be shorted out to have this effect.
Somewhat unlikely. Resisters tend to go "open" (infinite resistance)
rather than "short" (zero resistance). Don't forget, if resistors are
used to slow the motor in the manner suggested, then they must be in
series with it. Me, I'm not convinced that this is the actual design,
and that the fault is a bit less obvious.

---
Jay (remove dashes for legal email address)

[Larry Rogers]

Jay
I tend to agree with your observation about the design of the circuit,
HOWEVER..... checking the resistor pack appears to be a rather easy
approach. Of course, after I have spent a couple of hours standing on my
head upside down in the passenger foot well, I may change my mind.

Another suggestion I have received is that the control head in the console
has developed a problem. The switch has gone bad or relay is out. But I'm
not sure how to get the trim off around the gear shift lever. Haynes manual
not a big help. And none of the local parts houses have (or even know what
I'm talking about) a nylon-type pry bar for the trim. I don't want to scrap
that stuff trying to get it off. Any ideas on that? What do you use? And
just where are the clips located? I don't want to be jacking it up at the
corner when the clip is in the middle. Done that before in the old Mercedes
and cracked the trim. Bummer.

And even if I do get it out, what am I looking at? Back to the problem of
locating diagrams and flow charts. Yea, the resistor pack seems to be the
easiest to check tonight.

Larry
In the back yard, under the oak.

[Ray O]

Post by Larry Rogers
Jay
I tend to agree with your observation about the design of the circuit,
HOWEVER..... checking the resistor pack appears to be a rather easy
approach. Of course, after I have spent a couple of hours standing on my
head upside down in the passenger foot well, I may change my mind.
Another suggestion I have received is that the control head in the console
has developed a problem. The switch has gone bad or relay is out. But I'm
not sure how to get the trim off around the gear shift lever. Haynes
manual not a big help. And none of the local parts houses have (or even
know what I'm talking about) a nylon-type pry bar for the trim. I don't
want to scrap that stuff trying to get it off. Any ideas on that? What do
you use? And just where are the clips located? I don't want to be jacking
it up at the corner when the clip is in the middle. Done that before in
the old Mercedes and cracked the trim. Bummer.
And even if I do get it out, what am I looking at? Back to the problem of
locating diagrams and flow charts. Yea, the resistor pack seems to be the
easiest to check tonight.
Larry
In the back yard, under the oak.

Here are some instructions on removing the trim around the shifter:
http://www.pro-fit-intl.com/Adobe/LX-70-99.pdf

[Larry]

Ray
Thanks for the link. Looks like their phone holder works well. Loved
their directions on the trim.

Larry
In the back yard, under the oak.

[Ray O]

Post by Larry
Ray
Thanks for the link. Looks like their phone holder works well. Loved
their directions on the trim.
Larry
In the back yard, under the oak.

You're welcome!
Good luck with the project!

[Nick C Topolos]

Post by Larry
I have a '99 RX300, 201K miles. The other day, when the AC reached the set
temperature level, the fan speed reduced, as it is supposed to do. I wanted
a little more air, so I reached over and turned up the fan speed control.
Not the temperature control on the left, but the speed control on the right
side. Well, it went to full speed and stayed there. No matter what I do, it
will not reduce speed from full blast fan. This has been going on for a
couple of weeks now. I have disconnected the battery overnight to drain the
electric system, reconnected it the next morning, and still the same
thing... full speed fan. Any ideas?????
Larry
In the back yard, under the oak.

Larry, My manual shows 10 clips around the console. The instructions
keep repeating to tape the end of a screwdriver to remove.
Unfortunately, I didn't purchase the electric/electronics manual.
Nick

[Larry]

Nick
Does it specify gray duck tape or black duck tape?

Larry
In the back yard, under the oak.

[Richard J Kinch]

Post by Larry
Well, it went to full speed and stayed there.

If there's a full-speed fan relay to cut out all the resistors, then it
could be stuck on. Not sure if your car uses this, but it is the typical
wiring.

[Jay Somerset]

On Fri, 08 Jun 2007 18:12:44 -0500, Richard J Kinch

Post by Richard J Kinch

Post by Larry
Well, it went to full speed and stayed there.

If there's a full-speed fan relay to cut out all the resistors, then it
could be stuck on. Not sure if your car uses this, but it is the typical
wiring.

I agree -- if this is the design, it is the most logical fault point.
---
Jay (remove dashes for legal email address)

[Larry Rogers]

Update.... Thanks very, very much for the diagrams, whoever you are!
They helped more than you know. The saga continues. On Thursday, the fan
that had been running full blast, suddenly quit! Nothing! No air, no fan,
Nothing! And it's about a hundred degrees at lunch time. Now the priority
goes way up to get this fixed. Full speed AC fan in Florida in the summer
time is not that big a disadvantage. But no AC at all!!?! Now that's a
problem.
Anyway, what I have found so far... the Blower Motor Control Relay gives
a bad readout. Power In OK, Power Out OK, Ground In OK, Ground Out NG (No
Good). By jumping the contacts, fan runs full speed again. So the fan motor
is OK. The speed dial and the temperature dial still have no effect on the
fan speed, but I think that may be due to the bad reading from the Control
Relay. So I checked the parts source for a new one and the closest is in
Miami and cost $230. Bummer!! This thing is smaller than a pack of cards!. I
opened it up and no apparent cans were popped (capacitors). So whatever is
bad is probably on the circuit board. And I can't get into it that far
(tamper proof design). So now I'm on the hunt for a junked / wrecked RX300
to obtain parts from.

Larry
In the back yard, under the oak.

[mcbrue]

Have just finished an extensive consult with tha boyz in tha bak. An
them has come up wif two alternaters - er - coupla different wayz ta
go here. One - ya kin do whut you is supposed ta do in the florida
summer an stay under thet oak and not move much or two, ya culd just
go down to tha kudzu store an have them ole boys fix it fer ya -
shouldn't be no more than a couple thousand. Seems to me they charge
more than the MB boys do to fix each problem, just have fewer of them,
so their total take is about the same or a bit higher.

mcbrue under the bridge in the trailer down by the river

[GIga]

So, you're not only a clueless, obnoxious, a**hole, but you're a racist too.
How appropriate is that!

Post by mcbrue
Have just finished an extensive consult with tha boyz in tha bak. An
them has come up wif two alternaters - er - coupla different wayz ta
go here. One - ya kin do whut you is supposed ta do in the florida
summer an stay under thet oak and not move much or two, ya culd just
go down to tha kudzu store an have them ole boys fix it fer ya -
shouldn't be no more than a couple thousand. Seems to me they charge
more than the MB boys do to fix each problem, just have fewer of them,
so their total take is about the same or a bit higher.
mcbrue under the bridge in the trailer down by the river

[mcbrue]

Post by GIga
So, you're not only a clueless, obnoxious, a**hole, but you're a racist too.
How appropriate is that!

Post by mcbrue
Have just finished an extensive consult with tha boyz in tha bak. An
them has come up wif two alternaters - er - coupla different wayz ta
go here. One - ya kin do whut you is supposed ta do in the florida
summer an stay under thet oak and not move much or two, ya culd just
go down to tha kudzu store an have them ole boys fix it fer ya -
shouldn't be no more than a couple thousand. Seems to me they charge
more than the MB boys do to fix each problem, just have fewer of them,
so their total take is about the same or a bit higher.
mcbrue under the bridge in the trailer down by the river- Hide quoted text -

- Show quoted text -

So Glga, what is racist in the above? Sorry, but I don't understand
your racist accusation here. Perhaps you think Floridians are a
particular race and I am prejudiced against them? Or is it the
reference to the Kudzu store - no, plants just don't equate to human
status. Oh well ... guess I will wander off and see if I can find some
cows to eat some kudzu - not that I have anyting against cows, as a
matter of fact some of my best friends are cows.

[Larry]

McBrue
I think you miss the point. GI Georgia might be right! Maybe kudzu did
come over onboard the Amistad. I never thought about that before!! If that's
true, that would make them cows about as racist as the LAPD, abusing kudzu
like that. Why, I might even have to suspend my experiments with kudzu.
Since corn is in such short supply, what with ethonol demand, it's been hard
finding enough ingredients to keep the "refinery" going. Have been
experimenting with ground-up kudzu to make "green tea." Now I'm gona haf to
stop, all because GIga pointed out that abusing kudzu is racist. Boy, I'm
glad he did that. Keeps me out of a lot of trouble.

Larry
In the back yard, under the oak.

[GIga]

<grin>

Well done Mr. Larry

Post by Larry
McBrue
I think you miss the point. GI Georgia might be right! Maybe kudzu did
come over onboard the Amistad. I never thought about that before!! If that's
true, that would make them cows about as racist as the LAPD, abusing kudzu
like that. Why, I might even have to suspend my experiments with kudzu.
Since corn is in such short supply, what with ethonol demand, it's been hard
finding enough ingredients to keep the "refinery" going. Have been
experimenting with ground-up kudzu to make "green tea." Now I'm gona haf to
stop, all because GIga pointed out that abusing kudzu is racist. Boy, I'm
glad he did that. Keeps me out of a lot of trouble.
Larry
In the back yard, under the oak.

[Richard J Kinch]

Post by Larry Rogers
So I checked the parts source for a new one and the closest is in
Miami and cost $230.

This is some module that contains a relay, or just the relay itself?

I would think could use any relay of equal or higher current rating from
the auto parts store, and patch that in, if that is the failed component.

Typically these days such a relay is just a big fuse-shaped thing in the
fuse block, on "ordinary" cars.

[Larry]

Richard
Nope! This is not your typical relay. This baby takes in both positive
voltage and ground input, reads it, and outputs the appropriate amperage to
the fan motor to control the speed. At least that's what I think is
happening. At any rate, there are five or six capacitors mounted on top of a
circuit board and another board underneath (that I can't get to without
destroying the entire unit) and a heat sink on the back side. So it appears
that this thing is regulating amperage to the motor to control speed.
Sad part is, I'm not sure this is the only problem. The fan went to high
speed and stayed there. It ran like that for about a week, then quit running
altogether. When it stopped running, I tore out the kick panels and started
looking for problems. But what if I replace this thing only to find out that
something else was giving it a bad input? Control dial on the dash stuck in
the open position and causing this unit to blow?
At any rate, I am searching the junk yards for an organ donor. A buddy
of mine spotted a wreck in a backyard yesterday on his way to work. Am
trying to contact that victim to see if they will part with the remains.

Larry
In the back yard, under the oak.

[Richard J Kinch]

Post by Larry
At any rate, I am searching the junk yards for an organ donor.

In the meantime, I would consider just hot-wiring the fan so it ran at full
speed, so at least you have something in the heat.

[Larry]

Yep!! Got them wires twisted together and dangling down to the floorboard.
Another thing I had been meaning to do was to change the AC cabin filter as
part of the routine maintenance. When I got into this problem, the filter
was easily accessible, so I pulled it out. That thing had never been
changed!! It's a wonder any air at all got through. Now, on high speed, it
will blast you back into the seat.

Larry
In the back yard, under the oak.

[mcbrue]

Hey Larry! Do you mean the stealership guys haven't been changning or
cleaning the cabin air filter? I thought they were supposed to do that
as part of the $150 oil change. Maybe I will check up on those guys -
hard to do though, cause they all eat Kudzu and write in those funny
little characters. (Really I like Kudzu - some of my best friends eat
it and like it also. As a matter of fact, I have been trying to get
the Petunia Club downtown to start planting it in the flower beds, but
they are so uptight about some things!)

mcbrue under the bridge in the trailer down by the river

[Larry]

Yea, they must have been ripping the doctor lady that used to own this
thing. She gave me stacks of receipts showing how good she maintained the
car, always had it serviced on time, rotated the tires, filled the
windshield washer fluid.... you know.. all the important stuff. When I got
it from her, I had to do the minor stuff like change the radideator hoses
and fanner belts and batteries and braking pads and fuel filters (that got
rid of that weird hesitation she complained about) and some other
unimportant stuff that the dealer guys just couldn't be bother with (or
maybe couldn't find). But that's OK... I'm happy. It starts when I turn the
key and gets me back home everytime (at least so far) and the girls tell me
how pretty it is and the boys all wish they had one. Life is good.

Larry
In the back yard, under the oak.

[Larry]

It's Fixed!!!! The junk yard coughed up a good part today and the AC
now functions as advertised!! The Blower Motor Control Relay was bad.
Plugged in the replacement about half an hour ago and it works perfectly.
Just an observation.... when I changed the cabin air filter (the one
located behind the glove box) it was clogged!!!! I can't begin to tell you
how badly it was stopped up. But now with the new filter, the volume of air
flowing out of the vents is tremendous. I can't help but wonder if the
restricted air flow somehow caused the Relay to over heat and malfunction
(short, open, whatever)?? A five dollar air filter cost me $120 for a used
Control and hours of sweating, not to mention the cussing.
And, Yea, how come the service guys didn't do the routine replacement
when the good doctor lady owned it and took it to them all the time? Huh?
How come?

Larry
In the back yard, coolly under the oak.

[Richard J Kinch]

Post by Larry
I can't help but wonder if the
restricted air flow somehow caused the Relay to over heat and malfunction
(short, open, whatever)??

No, unless the air was somehow cooling the relay.

Restricting airflow through a fan makes it draw *less* current, because it
is doing less work.

[Xplant]

I don't agree-- just because the air moving through the filter is resrticted
doesn't mean the fan isn't 'trying as hard'. I say the fan would be at max
power despite the amount of air movement through the filter.

Post by Richard J Kinch

Post by Larry
I can't help but wonder if the
restricted air flow somehow caused the Relay to over heat and malfunction
(short, open, whatever)??

No, unless the air was somehow cooling the relay.
Restricting airflow through a fan makes it draw *less* current, because it
is doing less work.

[Richard J Kinch]

Post by Xplant
I don't agree-- just because the air moving through the filter is
resrticted doesn't mean the fan isn't 'trying as hard'. I say the fan
would be at max power despite the amount of air movement through the
filter.

Your intuition is incorrect.

Put a meter on the fan and try it if you don't believe me.

[Jay Somerset]

On Fri, 15 Jun 2007 17:34:21 -0500, Richard J Kinch

Post by Richard J Kinch

Post by Xplant
I don't agree-- just because the air moving through the filter is
resrticted doesn't mean the fan isn't 'trying as hard'. I say the fan
would be at max power despite the amount of air movement through the
filter.

Your intuition is incorrect.
Put a meter on the fan and try it if you don't believe me.

Richard is right, Xplant. If ther airflow is blocked, then the fan
will speed up, and draw less current. It has to do real work to push
air. If ther air can't be pushed, then all the fan motor has to do is
spin the fan against its own internal friction. Less opposing force
means less power drawn.

If you don't believe this, take a vacuum cleaner with a hose, start it
up, and plug the hose with your hand. Listen to the motor speed up.