Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > Porsche 911 Technical Forum

Closed Thread
 
LinkBack Thread Tools Rating: Thread Rating: 1 votes, 1.00 average.
Author
Thread Post New Thread    Closed Thread
Registered User
 
Join Date: May 2002
Location: St Louis
Posts: 4,209
Footwell blower thread closed?

Remember this thread? "Help! Does anyone understand the footwell blower circuit?"

It is closed.

I wanted to ask if anyone saw a reason that Porsche made the footwell blowers only come on with the engine compartment blower operating.

The way the original circuit worked was the output current from the relay that goes to the main blower was sensed with several turns of wire creating a magnetic field around a reed switch that when a certain field strength was reached turned on the relay that powers the footwell blowers. The proposed mod (jumper across the reed switch) turns on the footwell blowers whenever the main blower is has 12 volts applied, a subtle but distinct difference. Is there any reason the footwell blowers shouldn't run without positive pressure in the ducts?

My footwell blowers don't work and reading the thread got me troubleshooting. Everything works except the controller. should I try to repair the reed switch or just jumper it?
Old 01-23-2006, 10:03 AM
  Pelican Parts Technical Article Directory    #1 (permalink)
Used Up User
 
imcarthur's Avatar
 
Join Date: Jun 2003
Location: Toronto
Posts: 8,292
Garage
Rick

The thread was closed after Loren (of Lorenb vs Steve W fame) got offensive.

I think Mysterytrain's response on Pg 5 gives an answer:

"This isn't correct. They are two isolated fused circuits. The switched power that turns on the rear blower is also directed to the reed switch. It sits at the switch waiting for the rear blower to draw enough current to create a magnetic field that is strong enough to close the reed switch. Once the reed switch closes the current then flows thru the relay solenoid [only the solenoid, not the FW blowers] then to ground. Thats it. A very minimal additional current draw. A second 12 volt power feed comes into the controller on pin 3 and waits for the relay contacts to close [Yes, thats a normally open switch] when the contact closes that current flows out of terminal 4 and goes to the footwell blower speed switch. As for the speed switch, Positions 1 and 2 [ sometimes zero] send power to the dropping resistors to vary the blower speeds. Position 3 sends power directly to the solenoid of an AUX relay that then directs 12 volts from a 3rd power source to the footwell blowers for high speed operation. The reason for this is that appling the full 12 volts to the footwell blowers direct from the speed switch will burn up the contacts { yes, just like the headlight dimmer switch} So the relay is added to handle the high current.

I haven't dug into the logic circuit that controls the rear blower operation when the car is stationary. But it appears very likely that the rear blower could come on anytime these two conditions are met:
(1) the temperature sensor gets too hot
(2) the car is stationary.

Actually, I lot of modern cars have this feature."

I will be doing the mod in the spring. My problem sounds like your's - everything works except the footwells - which work when wired directly. The mod will solve it, without disturbing anything as per the thread.

Maybe Mysterytrain will chime in if he sees this thread . . .

Ian
__________________
'87 Carrera Cab

----- “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.” A. Einstein -----
Old 01-23-2006, 10:25 AM
  Pelican Parts Technical Article Directory    #2 (permalink)
Registered User
 
911Atlanta's Avatar
 
Join Date: Oct 2004
Location: Atlanta, GA
Posts: 75
Dude - save yourself a lot of time / anguish and bite the bullet on a new controller. I just did, and it was worth it to not have to F-around trying to find a work around for weeks. Either way, good luck !
__________________
Dan

'87 911 Carrera - Cabriolet
Old 01-23-2006, 12:12 PM
  Pelican Parts Technical Article Directory    #3 (permalink)
Registered User
 
Join Date: Mar 2004
Location: New Jersey
Posts: 1,861
wow the thread is closed because of a fight..sounds like another night of playing music in a jersey bar!

Rick, the main thrust of the mod was to solve a problem that carrera owners had when they altered the heating system..ie. removed the rear blower or substituted a Grainger motor for the OEM motor on the rear blower. When the rear blower was gone then the footwells would not work. Jumpering out the reed switch allows you to restore operation to the footwell blowers. I've looked at the circuit and I have to admit that I don't understand the logic in the reed switch. I only reason I can see, and I think its lame, is that it monitors the operation of the rear blower. If that rear blower fails then the system fails. With all the noise from the engine and fully operational footwell blowers the rear blower you might never know the rear blower failed and since its tied to the overtemp sensor that feature would never work. So now a new question..was the rear blower effective in helping cool the engine and was there a real heat issue when the car was standing still?
As to troubleshooting your footwell blowers..you might want to check the inline fuses if they are installed on your car. Then I would apply 12 volts to each of the blowers to test them to see if they work. After that, its time to dig into the circuits from the old thread and narrow down what is working and what is not.

wow, they really closed that thread! Thanks for the pictures Ian!
__________________
Peace, Ron
www.ronorlando.net
78SC Targa 3.2 SS, 964 cams, CIS, SSI's,Dansk
Own a gun and you can rob a bank , own a bank and you can rob the world.
Old 01-23-2006, 12:51 PM
  Pelican Parts Technical Article Directory    #4 (permalink)
Used Up User
 
imcarthur's Avatar
 
Join Date: Jun 2003
Location: Toronto
Posts: 8,292
Garage
Hi Ron

I hoped you'd jump in - since I was quoting you . . .

I was subscribed to the thread & saw the exchange on the weekend(?). Loren's meds wore off again & he dumped on wavey for his non-technical contributions to the thread. I guess the mods deleted those bits & closed the thread.

I archived the mod on my Rennlist site here - Controller Mod

Ian
__________________
'87 Carrera Cab

----- “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.” A. Einstein -----
Old 01-23-2006, 01:18 PM
  Pelican Parts Technical Article Directory    #5 (permalink)
Registered User
 
ianc's Avatar
 
Join Date: Dec 2004
Location: Novato, CA
Posts: 3,062
Wonder why it was closed? Seems like chopping a couple posts would have done the trick...

ianc

P.S. - No prob on the pics Ron, let me know if you need more.
__________________
BMW 135i. Nice. Fast. But no 911...

"I will tell you there is a big difference between driving money and driving blood, sweat and tears." - PorscheGuy79
Old 01-23-2006, 01:23 PM
  Pelican Parts Technical Article Directory    #6 (permalink)
Registered User
 
Join Date: May 2002
Location: St Louis
Posts: 4,209
Quote:
Originally posted by imcarthur
I archived the mod on my Rennlist site here - Controller Mod

Ian
That's pretty cool!
Old 01-23-2006, 02:03 PM
  Pelican Parts Technical Article Directory    #7 (permalink)
Registered User
 
aj88cab's Avatar
 
Join Date: Nov 2003
Location: Marietta, GA (Atlanta)
Posts: 792
Garage
Quote:
Originally posted by Mysterytrain
wow the thread is closed because of a fight..sounds like another night of playing music in a jersey bar!
LOL! I've been in few of them Jersey Bars back in the day! I visit family in Brigantine every summer. If your playing I might come look you up.

If you posted or subscribed to the old thread I think you can still access it thru your User CP. Offending posts have been deleted.

Now as for my footwell blowers, they still do not work correctly. Dan's advice above is my only (smart) option left.

However, I got rather intimate with the control circuit last weekend and discovered a few more things. The power for the control unit enters at pin 12. That power comes from the ignition switch and is on when the ignition switch is in the "RUN" position, but not in the "Accessory" position. This is the same source of power that operates the FW blower relay (that which runs THRU the reed switch contacts). The diagram Ian posted does not appear to be correct since it shows this power tapping off of the engine blower circuit. The source of this power (from the ignition switch) is indicated on the wiring diagram in the Bentley Manual. I also confimed the path by visually tracing it on the control unit. As a final test I removed both rear fuses and the front FW fuse plus the front relay and then jumpered the relay with the ignition in the run position and the FW Blowers relay closes. This seems to indicate that jumpering the reed switch would cause the footwell blowers to run any time the engine is running, even with the rotay switch in the "0" position since that position is not really OFF. I really hope I am wrong about this but........

This is the corrected diagram (w/o the jumper shown)




Andrew
__________________
'88 Carrera Cab 3.2 Diamond Blue Metallic - ERP Polybronze Bushings, ERP Monoballs, SW Chip, Bilstein Sports, 930S Steering Wheel, DAS Rollbar, Sparco 5pt Harness, Hunsaker Sport Seats, Dansk Pre-Muffler, MK 1in-1out Exhaust, Magnecor KV8.5 Wires
'86 944NA, Sunroof Delete, Track Rat, Full Cage
'72 914 1.7 Guards Red / '02 Audi S4 Light Silver Metallic
Old 01-23-2006, 02:17 PM
  Pelican Parts Technical Article Directory    #8 (permalink)
Registered User
 
Join Date: Mar 2004
Location: New Jersey
Posts: 1,861
One of the odd things about the drawing that we have been working from is the Over temp circuit. If the drawing is correct, then when the car is standing still with the engine running and hot, the rear blower should come on..and the footwell blowers also will begin to run if any of the speed switch settings have been selected and '0' isn't really an off setting?? That doesn't seem correct and I think it was something I was questioning on the original thread. I went back and looked at the controller pictures...more questions. We don't know much about the origin of the controller flow chart drawing..but we do know its very crude. There a couple of transistors inside the controller...more logic switches? That power going to the FW relay could also be controlled by one of those guys and dependant on the state of things in the IC. We need a real schematic of the controller or a donor for one of us to draw out. I think we also need to pull information on what year cars the mod works on and the actually wiring of those cars. Example: I picked up a 3 speed heater console, mint old stock...with a 6 pin connector on the end of the harness. All the pin outs look right except for pins 4 and 6..which also got me thinking. Is the drawing of the 3 speed switch correct or was my connector miswired???
__________________
Peace, Ron
www.ronorlando.net
78SC Targa 3.2 SS, 964 cams, CIS, SSI's,Dansk
Own a gun and you can rob a bank , own a bank and you can rob the world.
Old 01-23-2006, 06:43 PM
  Pelican Parts Technical Article Directory    #9 (permalink)
Registered User
 
Join Date: Mar 2004
Location: New Jersey
Posts: 1,861
opps, Ian thats great that you posted the mod!!
__________________
Peace, Ron
www.ronorlando.net
78SC Targa 3.2 SS, 964 cams, CIS, SSI's,Dansk
Own a gun and you can rob a bank , own a bank and you can rob the world.
Old 01-23-2006, 06:47 PM
  Pelican Parts Technical Article Directory    #10 (permalink)
Detached Member
 
Hugh R's Avatar
 
Join Date: May 2003
Location: southern California
Posts: 23,528
Hey Ian:

I just wanted to say Hi. I had such a nice evening with you guys last summer when I was there. I'm currently in Shreveport, Louisiana on another film.
__________________
Hugh
Old 01-23-2006, 08:24 PM
  Pelican Parts Technical Article Directory    #11 (permalink)
Registered User
 
randywebb's Avatar
 
Join Date: Nov 2004
Location: Greater Metropolitan Nimrod, Oregun
Posts: 10,043
Has anyone actually met Loren in person??
__________________
"A man with his priorities so far out of whack doesn't deserve such a fine automobile."

- Ferris Bueller's Day Off
Old 01-23-2006, 08:32 PM
  Pelican Parts Technical Article Directory    #12 (permalink)
Used Up User
 
imcarthur's Avatar
 
Join Date: Jun 2003
Location: Toronto
Posts: 8,292
Garage
Here is the original thread btw Help! Does anyone understand the footwell blower circuit?

Ron - Yes, I archived it in my Autoheat Trouble Shooting pages that I've been gradually building for a year. But I have to wait 'til spring to try the mod myself.

Hugh - Shreveport - one of the few places in the east I haven't been. Is this where Disney moved the New Orlean's shoot you were starting?

Randy - If anybody does meet him, you might want to take a stick & poke him first - to see if you get the good Loren or the bad Loren . . . his attack on Wavey was unprovoked & uncalled for. He must have searched for a previously posted thread & just let loose.

Ian
__________________
'87 Carrera Cab

----- “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.” A. Einstein -----
Old 01-24-2006, 03:12 AM
  Pelican Parts Technical Article Directory    #13 (permalink)
Registered User
 
Join Date: Feb 2004
Location: louisiana
Posts: 1,481
88 is right, at least for mine. FW's blow at very slow speed whenever the engine is running with the jumper. Use to they only came on at that very slow speed when the flaps were pulled up and switch was at zero. If my heater boxes were perfect this might not matter, but i stll get a little heat comming out with everything off and closed.
Old 01-24-2006, 03:23 AM
  Pelican Parts Technical Article Directory    #14 (permalink)
Registered User
 
ianc's Avatar
 
Join Date: Dec 2004
Location: Novato, CA
Posts: 3,062
Quote:
Use to they only came on at that very slow speed when the flaps were pulled up and switch was at zero. If my heater boxes were perfect this might not matter, but i stll get a little heat comming out with everything off and closed.
Mine only come on with the levers pulled up (as I believe according to the diagram they should). This makes me think your levers are not going down all the way, and flapper boxes not shutting completely; particularly if you're still getting heat in the car when it should be off,

ianc
__________________
BMW 135i. Nice. Fast. But no 911...

"I will tell you there is a big difference between driving money and driving blood, sweat and tears." - PorscheGuy79
Old 01-24-2006, 08:04 AM
  Pelican Parts Technical Article Directory    #15 (permalink)
Registered User
 
Join Date: May 2002
Location: St Louis
Posts: 4,209
Is this thing the right size?

http://www.newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/partDetail.jsp;jsessionid=PPVEJWL3VP5IKCXDUY0SFGAK 2OTCGIV1?SKU=01C1811&N=0
Old 01-24-2006, 08:34 AM
  Pelican Parts Technical Article Directory    #16 (permalink)
Registered User
 
Join Date: Mar 2004
Location: New Jersey
Posts: 1,861
It was late last night when I revisited this thread. This morning I have some different thoughts. If the actually wiring is as AJ states then the the reed switch circuit makes a little more sense because it is totally independant of the rear blower circuit for its power but here is still a nagging question that goes back to overtemp and speedometer connections. If the two conditions are met..engine is over the temperature set point and the car is not moving then the overtemp switch and speedo connections are now controlling the rear blower if the heater is not already on... the rear blower should come on, but only the rear blower not the footwells. In the drawing above[ the original and the AJ's] that is not the case..whenever the rear blower draws enough current it closes the reed switch and power is directed to the speed selector switch. I'm thinking the logic circuit is also tied to the second relay.
I printed out the image of the back of the controller PC board and tried to highlight the traces from the reed switch ends. Although it does appear that AJ is correct in that the 12 volt feed comes from pin 12..it is not a clean shot to the switch. Most notable is the transistor at the top of the reed switch. We really need to sit down and draw the damn thing out so that we can see what is going on.
Another question for Jerry and AJ. Since we all agree that the blowers are controlled by two circuits..the basic heater circuit and secondly, the speedometer and the overtemp switch are you guys sure that those connections are still good and that the overtemp switch is good? I know AJ has swapped out his old controller for a new one. That should rule out the controller. But if the logic on the controller continues to think the engine is hot (bad sensor) then it will always be powering up the first relay..and with the jumper in place the footwell blowers
__________________
Peace, Ron
www.ronorlando.net
78SC Targa 3.2 SS, 964 cams, CIS, SSI's,Dansk
Own a gun and you can rob a bank , own a bank and you can rob the world.
Old 01-24-2006, 12:26 PM
  Pelican Parts Technical Article Directory    #17 (permalink)
Registered User
 
randywebb's Avatar
 
Join Date: Nov 2004
Location: Greater Metropolitan Nimrod, Oregun
Posts: 10,043
Yes, I realize it was unprovoked. I'm just curious what's wrong with him. It's the behavioral ecologist in me...
__________________
"A man with his priorities so far out of whack doesn't deserve such a fine automobile."

- Ferris Bueller's Day Off
Old 01-24-2006, 06:03 PM
  Pelican Parts Technical Article Directory    #18 (permalink)
 
Now available:  101 Projects for Your Porsche Boxster!
Used Up User
 
imcarthur's Avatar
 
Join Date: Jun 2003
Location: Toronto
Posts: 8,292
Garage
Hmmm. It seems Loren's rampage continues. He sent me a personal VERY offensive email tonight. Not worth repeating here but I will forward to Wayne. Sigh . . .

Ian
__________________
'87 Carrera Cab

----- “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.” A. Einstein -----
Old 01-24-2006, 07:22 PM
  Pelican Parts Technical Article Directory    #19 (permalink)
Registered User
 
ianc's Avatar
 
Join Date: Dec 2004
Location: Novato, CA
Posts: 3,062
Quote:
Yes, I realize it was unprovoked. I'm just curious what's wrong with him.
Who cares? At least he's gone. He ruined my thread with his antisocial behavior.

Quote:
He sent me a personal VERY offensive email tonight.
Ha! Sorry about that Ian; I strongly suspect he meant to send it to me instead (the other Ian). At least you're on another continent...

ianc
__________________
BMW 135i. Nice. Fast. But no 911...

"I will tell you there is a big difference between driving money and driving blood, sweat and tears." - PorscheGuy79
Old 01-24-2006, 07:33 PM
  Pelican Parts Technical Article Directory    #20 (permalink)
Closed Thread

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 10:34 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2016 Pelican Parts - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.