Help! Does anyone understand the footwell blower circuit? - Page 3

einreb · 01-05-2006, 05:32 PM

Quote:

Originally posted by Mysterytrain
Great news...I didn't want my theory on how the rear blower controlled the footwell blowers to be total fantasy. So, it appears that backdating the heat on a carrera is now a simple proceedure that can be accomplished one of two ways. You can open the Control module and jumper around the reed switch or you can modify the module socket connections by removing the green/red wires from terminals 5 and 6. Then remove and relocate the black wire from terminal 4 to the 5 or 6 terminal.

It works!!!!!!

i removed and taped 5 and 6 and relocated 4 to the 6 spot.

this is the holy grail of 911 tech crap. seriously, wayne might as well lock up the tech section.

Nice job and thanks for figuring this out.

-Bernie

Rot 911 · 01-05-2006, 05:33 PM

Quote:

Originally posted by efhughes3
So, the idea here is to jumper the connections of the reed switch on the back side of the board? Is that the reed switch there in the center, the part with the silver coil wrapped around it like a spring?

That's the idea, but before I do it I want to get confirmation from Ron.

efhughes3 · efhughes3's Garage

Nice Bernie!

Rot 911 · 01-05-2006, 05:58 PM

I'm hoping to try out jumping the reed switch first. That seems easiest to do. If that doesn't work then I will go with Bernie's solution.

einreb · 06:01 PM

Quote:

Originally posted by Kurt V
I'm hoping to try out jumping the reed switch first. That seems easiest to do. If that doesn't work then I will go with Bernie's solution.

I agree that may be the easiest solution if you care to pry apart the control box. I tend to take the path of most resistance (no pun intended

).

The only minor thing to note is that my 5 and 6 wires were yellow with a red line and dealing with that pin connector was a biatch. the numbers for the pins are clearly marked. i.e. pay attention to the pin numbers and not the wire colors. 4 was black. I did a bit of 'pin connector wiring' when I did my 3.6 swap and didn't enjoy it then either.

Funny thing, those footwell blowers are my wife's favorite thing about that car. Plenty o' heat! I also discovered I killed my battery since I let it sit too long without running it this winter. dayum. I had to jump it to test it out, but i think i ran it down way too far and its not holding a charge. Oh, well... its great to cross another 'to do' off the porsche list!

-bernie

efhughes3 · efhughes3's Garage

Without footwells, my system is semi-useless. I'm really looking forward to a solution.

Rot 911 · 01-05-2006, 06:04 PM

Quote:

Originally posted by einreb
I agree that may be the easiest solution if you care to pry apart the control box.

I opened the control box tonight. Box is aluminum and lifting up the edge and sliding out the internals took all of about 2 minutes.

ianc · 01-05-2006, 06:07 PM

You guys are fabulous! I've seen this issue discussed a million times, and now FINALLY someone's figured it out! Fantastic! Excellent work Ron!

Now, if I could just get my engine running properly, I could devote some time to this... ;(

ianc

dfink · 01-05-2006, 06:12 PM

Just a reiteration of an earlier note. I also previously tried to jumper the reed switch to no avail. But this was because of some other issue with the controller. Same symtom footwell blowers no worky. This fix is only if everything else was working before the change to or elimination of the rear blower. If your footwell blowers just don't work the jumper solution won't do the trick. In my case a different controller solved problem even with a Dayton motor. Just something to keep in mind if the jumper doesn't work for someone.

Rot 911 · 01-05-2006, 06:18 PM

My blowers work when I jump the blower relay in the engine compartment. Removed the engine blower.

aj88cab · aj88cab's Garage

Quote:

Originally posted by einreb
It works!!!!!!

i removed and taped 5 and 6 and relocated 4 to the 6 spot.

this is the holy grail of 911 tech crap. seriously, wayne might as well lock up the tech section.

Nice job and thanks for figuring this out.

-Bernie

Just a quick reminder that might get lost in all the excitement. The modification to the wires in the connector only works with backdated systems with the engine blower removed. If the engine blower is still in the system this mod will have the engine blower and the footwell blowers on the same fuse. Not good.

If you still have an engine blower you must do the internal jumper at the reed switch. The end result of this jumper is that the footwell blowers will run even if the engine blower is toast.

Andrew

efhughes3 · efhughes3's Garage

I think most here are trying to keep the footwells working with the backdate setup, I know I am.

Rot 911 · 01-06-2006, 05:31 AM

bump

Mysterytrain · 01-06-2006, 06:04 AM

Hey great news..this has been an issue for a long time here.
Andrew, thats not true about the all blowers being on the same fuse after the mod. What is happening with the mod is you are removing the reed switch ( the permissive element ie: rear blower works, then footwells work) from the circuit. The rear blower is fused from fuse 1 on the rear panel and the footwells from fuse 2. The OEM wiring has the rear blower and the footwell relay solenoid on the same circuit and this doesn't change with the use of the jumper.

brcorp · brcorp's Garage

Great thread! How about a picture of a modded controller.

Mysterytrain · 01-06-2006, 06:29 AM

Kurt..great pictures! Here is a follow up on the circuit boards and two possible ways to modify the circuit. One from the back and one from the front. Again, I don't have the unit in front of me so let me know if the jumper placement is correct in the first picture. I sat here counting solder pads..I think its correct. As always with soldering don't overheat the pads and don't flow solder onto the pads near by. The mod shown in second picture might be easier for some people because it just connects the reed switch pigtails together. Its not as sexy as the first but you are less likely to over heat the pad and have the switch come loose. It appears that the factory didn't attempt a 90 degree bend and poke the ends of the reed switch thru the holes in the pads. Once we get all this sorted out I'll cut and paste it into another document to make it more of a how to..good work team!!

Mod one:

Alternate version of mod:

Rot 911 · 01-06-2006, 06:40 AM

Ron I plan on going with wire connecting the two ends of the reed switch together as you show in the second photo. I will do it tonight and post the results tomorrow. Your knowledge and the posting of the diagrams by the others in this thread might make for an easy solution to keeping the footwell blowers!

ianc · 10:06 PM

Here's a question though. I have read in a few places that in the later models, the factory changed the circuit so that position '0' on the rotary switch makes the footwells run all the time, albeit very slowly. It seems to me that with this mod (removing the dependency on the main blower), if your blowers run at '0', they will always be running now, even in summer?

Anybody done it and seen this yet?

ianc

Edited later to say: This post was made by someone who just didn't quite get it yet.

rick-l · 01-06-2006, 09:40 AM

Did anyone "reverse engineer" (draw a schematic of) the control module? It is simple to do it with these old thru hole parts PCBs (as opposed to SMT with blind and buried vias etc).

I'm curious. Anyone got a dead one they can sell me (for postage cost)?

aj88cab · aj88cab's Garage

Quote:

Originally posted by Mysterytrain
Hey great news..this has been an issue for a long time here.
Andrew, thats not true about the all blowers being on the same fuse after the mod. What is happening with the mod is you are removing the reed switch ( the permissive element ie: rear blower works, then footwells work) from the circuit. The rear blower is fused from fuse 1 on the rear panel and the footwells from fuse 2. The OEM wiring has the rear blower and the footwell relay solenoid on the same circuit and this doesn't change with the use of the jumper.

Ron,

I think we agree on the the reed switch by-pass. Not a problem other than losing the "permissive" feature you mentioned.

The point that I was trying to make (and didn't do a good job of) was that the reed switch jumper is the only mod that will work with a engine blower still installed.

As for the engine blower and footwell blower being on the same fuse, yep, I was confused on that one. Don't know what I was thinking, I didn't sleep in a Holiday Inn last night

Quote:

Originally posted by Ianc

Here's a question though. I have read in a few places that in the later models, the factory changed the circuit so that position '0' on the rotary switch makes the footwells run all the time, albeit very slowly. It seems to me that with this mod (removing the dependency on the main blower), if your blowers run at '0', they will always be running now, even in summer?

Anybody done it and seen this yet?

ianc

Ianc

The "0" and "1" setting on the rotary switch are the same speed. I think this was the case for all Carreras but I don't have experience with the earlier Carerras. I believe this was done because if the footwell blowers are actually OFF the fan cage partially blocks the path of the heated air. The engineers decided they should run even when "OFF". Having said that my car will get mighty hot without the FW blowers working so I don't know how much air it blocks.

With the reed switch jumper the FW blowers will only run when the heater levers are up, just as they do normally. As Ron noted above all you are doing with this mod is by-passing the feature that won't let the footwell blowers run unless the engine blower is running.

Andrew