Carrera - Removing Engine Compartment Heater Blower

[scarceller]

Originally Posted by Jaskas

Yesyes!
Like this:

Very nice, a new simple controller that looks original. Even the concourse judges will be fooled!

Just be certain nothing can short out if bounced around inside the case.

Nice job

[Jaskas]

Yes, was a bit worried about short-circuits. I didn´t have any insulation shinking socks or similar in my hand just then, so i used electricians black tape... ( not shown in pics)

[scarceller]

Little off topic here,
but I'm also going to do similar thing to the Factory DME relay for the 84-89 cars. The DME relay is made up of 2 separate relays internally, one for the DME the other for the FuelPump. I plan to gut an old one I have and replace with 2 40Amp external relays. This will allow me to simply keep a few extra cheap spare relays in the Glove Box.

[Joe Bob]

Does anyone have a pic of the actual rear heater blower unit?

[scarceller]

Originally Posted by mikez

Does anyone have a pic of the actual rear heater blower unit?

This one is already SOLD but here is a picture of the blower and the inlet duct, the blower is in the rear engine bay left side:
FS - 84 Carrera rear heater blower

[Jaskas]

Originally Posted by mikez

Does anyone have a pic of the actual rear heater blower unit?

[Joe Bob]

Thanks...where does it mount?

I have a 3.6 in my SC, and planning on mounting footwell blowers. I'm using custom 993 HEs that need a cross over for both sides to work....., but I can't fit it in due to space under the longhood, body work on the back....cat and muffler are in the way.

[scarceller]

Originally Posted by mikez

Thanks...where does it mount?

I have a 3.6 in my SC, and planning on mounting footwell blowers. I'm using custom 993 HEs that need a cross over for both sides to work....., but I can't fit it in due to space under the longhood, body work on the back....cat and muffler are in the way.

Suggestion, if you are going to put in the front footwell blowers then DON'T bother installing the rear blower. I'd simply backdate the rear tin to the 74 style heater duct on the left side only and plumb that duct to the cross-over tube. So the cross-over tube gets it's input air from the left side behind the distributor, then the front blowers will pull air into the cabin. This idea will reduce pounds and clutter in the engine bay.

Or - you could simply let the cross-over tube draw air from the engine bay area and simply let the front blowers pull air into the cabin. Only danger with this is to be sure the cross-over tube is not drawing in exhaust. Bottom line is that the front blowers are more than enough to draw plenty of heat into the cabin you don't need any rear blower. My 84 car has no rear blower, engine tin backdated to 74 style and SSI heat exchangers then I simply run footwell blowers I have tons of heat even in 5deg F weather I have to turn the heat down.

[Jaskas]

Originally Posted by mikez

Thanks...where does it mount?

see pic no.3 above

[Talewinds]

I have the manual control heat ( dial control 0-3) in my 88'. I modified my OEM heater relay today in anticipation of removing the rear heater blower.
Now I have a problem, everything appears to work as prescribed, however, with the dial set to '0', the footwell blowers run at their slowest speed, even with the levers down. So, the footwell blowers never actually turn off with the key in the on position. It was a mild 60 degrees earlier today and while driving for a bit I was roasting in the car even with just the footwell blowers running at '0'.
This is a problem, others must have this issue going on that modified the relay also. I looked through all of these threads however and didn't see anything....

[scarceller]

Originally Posted by Talewinds

I have the manual control heat ( dial control 0-3) in my 88'. I modified my OEM heater relay today in anticipation of removing the rear heater blower.
Now I have a problem, everything appears to work as prescribed, however, with the dial set to '0', the footwell blowers run at their slowest speed, even with the levers down. So, the footwell blowers never actually turn off with the key in the on position. It was a mild 60 degrees earlier today and while driving for a bit I was roasting in the car even with just the footwell blowers running at '0'.
This is a problem, others must have this issue going on that modified the relay also. I looked through all of these threads however and didn't see anything....

First look at post 43 above.

Something is wrong in your car. Pos '0' on the rotary should always turn off the foot blowers are you certain they are running? I ask because even in pos '0' if the heat levers are up you get tons of heat because the engine fan pushes air through the exchangers (the pre-74 cars only used the main engine fan). Then also when you push down the red levers the 2 heater valves above the transmission close and only if these are closed can you really shut down the heat. Also if the red levers do not close the relay will not deactivate (Pin 9 and 11 are used for this). I suspect you may have a broken cable from the red levers to one or both valves or the valves are simply stuck open, I'd check this first.

Then I'd remove the controller and test for continuity between pin 9 & 11 when the levers are pulled up (key does not need to be in ignition for testing this), with them in up position the switch at the levers should close and pin 11 gets connected to pin 9 via the switch. When levers are down pin 9 should no longer be connected to 11, use a ohm meter or test light for testing. (See schematic on post #43) Basically when pin 9 gets shorted to pin 11 by the switch it activates the relay. If you use a test light: connect one side to power like at one of the rear fuses (find one with 12V even with key out) then connect other side to pin 9 in the harness, levers up light on, levers down light off.

Another test: with the relay installed and the key in 'RUN' you can test pin 4, which is the power feed to the front footwell blowers and rotary switch, it should not have 12V with the levers down and should read 12V with them up.

Hope this helps.

[Talewinds]

Indeed pins 9 and 11 have continuity when the red levers are up, and no continuity when the levers are down. Last week I went through and adjusted my heater dampers under the car so they both function correctly.
Pin 4, however, has 12v on it regardless of whether the red levers are up or down.
But things are starting to become clear on this issue now. Scarceller, the picture you posted way back at the beginning of this thread of the circuit tracings on the back of your heater controller, they differ somewhat from mine, although at first glance all of the solder connections look to be in the same place. On my circuit tracings, one end of the reed switch goes DIRECTLY to one end of FW blower relay coil. I could be completely mistaken so early in my meddling but it appears that if the reed switch is "made" or shorted as in the case of the jumper, the FW blower relay coil is going to energize regardless of the red lever position.
I'm going to do some more testing but on the particular type of heater controller board I (and some others) have that the reed switch and corresponding jumper can be abandoned and another jumper can be installed, one that makes a connection on the board between the red lever switch input directly to the FW blower relay coil.
Hopefully some pics will follow illustrating the differences in the circuit tracings on the backs of the controller boards.

[scarceller]

Originally Posted by Talewinds

Indeed pins 9 and 11 have continuity when the red levers are up, and no continuity when the levers are down. Last week I went through and adjusted my heater dampers under the car so they both function correctly.
Pin 4, however, has 12v on it regardless of whether the red levers are up or down.
But things are starting to become clear on this issue now. Scarceller, the picture you posted way back at the beginning of this thread of the circuit tracings on the back of your heater controller, they differ somewhat from mine, although at first glance all of the solder connections look to be in the same place. On my circuit tracings, one end of the reed switch goes DIRECTLY to one end of FW blower relay coil. I could be completely mistaken so early in my meddling but it appears that if the reed switch is "made" or shorted as in the case of the jumper, the FW blower relay coil is going to energize regardless of the red lever position.
I'm going to do some more testing but on the particular type of heater controller board I (and some others) have that the reed switch and corresponding jumper can be abandoned and another jumper can be installed, one that makes a connection on the board between the red lever switch input directly to the FW blower relay coil.
Hopefully some pics will follow illustrating the differences in the circuit tracings on the backs of the controller boards.

The end goal is for pin 4 to have 12v with levers up and 0v with them down. But even if pin 4 has 12V all the time if you move the rotary switch to '0' the front blowers should not get power, maybe something else is different. What year is the car? My car is a 84 and it has only 3 front blower speeds 1=lo 2=med 3=hi 0=off. Could it be that the later cars somehow had 4 speeds?

[Talewinds]

Yes. After searching and reading so many of these threads/posts there seems to be a trend, however slight. On your 84' and seemingly many other cars, setting '0' on the dial is "off", but I've noticed others that state that both settings '0' and '1' are low speed, or maybe just a slight speed difference. This appears consistent with some later cars and I'm betting those later cars (like my 88') also have the minute differences in the control board circuitry.
Why this minor factory change I can't hypothesize, nor do I want to. What I do want to realize is how to modify the heater controller in the engine compartment to allow the red levers to control the on/off of the footwell blowers, and I believe this is probable, and possibly simple.
Scarceller, you mentioned pins 9 and 11, when they make continuity by lifting the red levers, what passes through those contacts when the car is running? A simple 12v that goes to power the rear engine blower motor relay? Or some other convoluted electronics in that controller board?

[scarceller]

Originally Posted by Talewinds

Yes. After searching and reading so many of these threads/posts there seems to be a trend, however slight. On your 84' and seemingly many other cars, setting '0' on the dial is "off", but I've noticed others that state that both settings '0' and '1' are low speed, or maybe just a slight speed difference. This appears consistent with some later cars and I'm betting those later cars (like my 88') also have the minute differences in the control board circuitry.
Why this minor factory change I can't hypothesize, nor do I want to. What I do want to realize is how to modify the heater controller in the engine compartment to allow the red levers to control the on/off of the footwell blowers, and I believe this is probable, and possibly simple.
Scarceller, you mentioned pins 9 and 11, when they make continuity by lifting the red levers, what passes through those contacts when the car is running? A simple 12v that goes to power the rear engine blower motor relay? Or some other convoluted electronics in that controller board?

I was afraid you would ask about pin 9 and 11! Here goes.

Pin 11 is powered from the starter circuit and it's very wild setup the factory came up with. Pin 11 goes to the power side of the starter, they did this so that if the starter is cranking then pin 11 gets 12v and this in turn turns off the heat relay, the idea was to not have all the blowers possibly on while cranking. So when not cranking the starter coils are a very lo-resistance most likely a few ohms this in effect grounds pin 11 when not cranking but it's grounded actually through the starter windings! In any case the idea is that pin 11 has 12v while cranking and 0v (GND) if not cranking. Then if you pull up the levers pin 11 shorts to pin 9 and thus grounds pin 9 (so long as not cranking). Took me a while to figure this puppy out.

Also, pin 9 DOES NOT simply pick the relays! It goes through some other electronic chips that I never figured out that then pick the relays. Most important is that pin 9 goes ground to activate the controller and goes open circuit to deactivate.

You may also want to look at post #36 as it shows another alternative that simply can replace the heat controller with a very simple relay. Someone has also posted #56 to show how they simply de-gutted the stock controller and placed simple relays inside the tin following my wiring in Post #36. This is yet another nice solution. In my car I totally removed the controller altered the harness and simply use 2 simple relays. But I like Post #56 approach better as it keeps the harness 100% stock only the controller is altered.

[Talewinds]

Uuggggh, and I was afraid that would be the case, not as simple as it all really should be, but thanks for the clarification on 9 and 11 anyway. I'm going to keep banging my head against the wall on this...
There's got to be something straightforward in that controller circuitry that goes to 12v straight up, no monkey business when the red levers are pulled up. If I can isolate that, then i reroute that to the coil side of the footwell relay and presto.
Ya, I know, I'm probably just talking through what a dozen other guys have hypothesized about in the past and then just came to the conclusion that the tin had to be gutted and replaced w/ relays... I'll probably reach that conclusion too.

[scarceller]

Originally Posted by Talewinds

Uuggggh, and I was afraid that would be the case, not as simple as it all really should be, but thanks for the clarification on 9 and 11 anyway. I'm going to keep banging my head against the wall on this...
There's got to be something straightforward in that controller circuitry that goes to 12v straight up, no monkey business when the red levers are pulled up. If I can isolate that, then i reroute that to the coil side of the footwell relay and presto.
Ya, I know, I'm probably just talking through what a dozen other guys have hypothesized about in the past and then just came to the conclusion that the tin had to be gutted and replaced w/ relays... I'll probably reach that conclusion too.

You are NOT running the rear blower right? If this is the case you could maybe reroute the rear blower relay output to pin 4 to the front blowers. Sort of disable the front blower relay (small one) from picking and then simply jumper the output for the rear pin 5&6 over to pin 4. This is of course if pin 5 & 6 lose power with levers down. Idea is to have the larger relay (rear blower) take the place of the smaller one. But if you go through all this trouble I'd just can the electronics in the case and replace with one simple relay like shown in earlier post.

[Talewinds]

Originally Posted by scarceller

You are NOT running the rear blower right? If this is the case you could maybe reroute the rear blower relay output to pin 4 to the front blowers. Sort of disable the front blower relay (small one) from picking and then simply jumper the output for the rear pin 5&6 over to pin 4. This is of course if pin 5 & 6 lose power with levers down. Idea is to have the larger relay (rear blower) take the place of the smaller one. But if you go through all this trouble I'd just can the electronics in the case and replace with one simple relay like shown in earlier post.

Ahhh, getting warmer.
I've got to head off to skool now.
Let me mull this over some more during class and then I'll mess w/ the relay some more when I get home...

[Mysterytrain]

My 2 cents on this issue. Sometime in the mid 80's those factory engineers decided that '0' or 'Off' shouldn't really be off. I think the logic was an effort to save the bearings in the footwell blowers and/or prevent the squirrel cage from melting. It is my understanding that micro switch under the red levers the red levers should act as the master on/off switch for the circuit.
On an SC the red levers trigger a relay and that in turn powers up the engine compartment blower. Carrera's uses the same type of circuit in the engine compartment control box. I don't remember which relay is the 'master', but that one could be stuck in the closed position. You should be able to test it with the cover off and having someone lift the levers.

[scarceller]

Originally Posted by Mysterytrain

My 2 cents on this issue. Sometime in the mid 80's those factory engineers decided that '0' or 'Off' shouldn't really be off. I think the logic was an effort to save the bearings in the footwell blowers and/or prevent the squirrel cage from melting. It is my understanding that micro switch under the red levers the red levers should act as the master on/off switch for the circuit.
On an SC the red levers trigger a relay and that in turn powers up the engine compartment blower. Carrera's uses the same type of circuit in the engine compartment control box. I don't remember which relay is the 'master', but that one could be stuck in the closed position. You should be able to test it with the cover off and having someone lift the levers.

Ron, the larger relay in the controller is the master and it feeds the Rear Blower then all current (AMPs) to the rear blower are passing through the reed switch and only if enough current is drawn by the Rear Blower does the reed switch close. Once closed it powers the coil on the smaller relay which feeds the front blowers via the rotary switch. That's how my controller works, but Talewinds seems to imply that the reed switch in his controller is somehow wired differently but I can't imagine what else they would use the reed switch for? In my controller the idea is very simple: do not allow power to the front blowers unless the rear blower is installed and running (thus drawing current).

It could be that Talewinds simply has a bad controller.

Talewinds what is the part number on your controller?
My controller part # is 911.618.153.00