Carrera - Removing Engine Compartment Heater Blower

[sus911]

I have the exact same issue, however since my backdate I have never been able to get the footwell blowers to work through the relay.
Have a look here:
https://rennlist.com/forums/911-forum/1280140-automatic-heating-control-not-functioning-2.html

I'm yet to find the time to follow the advice given.

[eflight]

Bumping an old thread.

Anyone have a fix for a bad footwell blower relay, the small relay in the box? Is there a small relay I could wire in that would perform the function even if not an exact part replacement?

[GH85Carrera]

Originally Posted by eflight

Bumping an old thread.

Anyone have a fix for a bad footwell blower relay, the small relay in the box? Is there a small relay I could wire in that would perform the function even if not an exact part replacement?

This is one option.

[eflight]

Originally Posted by GH85Carrera

This is one option.

I saw that. But it requires you to gut the control box to get the bottom connector plate. I was wondering if anyone had just removed the old bad small relay and replaced it with something else.

I've been digging to try and figure out what the specs of that relay would be. Looks like it would be a 12V SPST relay. It looks like they used a SPDT relay, but tie the 2 poles together to get twice the rting from the relay. Some small mini relay looks like it would work. Not sure what amp ratting it would need though.

[wazzz]

Originally Posted by eflight

I saw that. But it requires you to gut the control box to get the bottom connector plate. I was wondering if anyone had just removed the old bad small relay and replaced it with something else.

I've been digging to try and figure out what the specs of that relay would be. Looks like it would be a 12V SPDT relay. Some small mini relay looks like it would work. Not sure what amp ratting it would need though.

Look for Durakool automotive pcb relay. Small enoufh to fit in place of the old relay and toufh enough to drive both footwells. SPST or SPDT will do the trick since you only need a simple switch. You'll have to carefully unsolder the bad relay and adapt wiring with short pieces of wire and heat shrink.

The ref. of the relay I bought is DG20-7011-35-1012. I bought 4 units. They are cheap. A couple of dollars each. You can find them anywhere like Mouser etc.

[scarceller]

In my personal car I removed that stock controller completely. I then also cut off the entire harness connector and I then wired the harness wires correctly to 2 modern day 40Amp relay plugs. Then the 2 modern day relays plug into the new relay plugs I put on the harness. The key here is to do this cleanly and professionally. Sure it changes the harness from stock to now using easily available 40 amp box relays.

Originally Posted by wazzz

Look for Durakool automotive pcb relay. Small enoufh to fit in place of the old relay and toufh enough to drive both footwells. SPST or SPDT will do the trick since you only need a simple switch. You'll have to carefully unsolder the bad relay and adapt wiring with short pieces of wire and heat shrink.

The ref. of the relay I bought is DG20-7011-35-1012. I bought 4 units. They are cheap. A couple of dollars each. You can find them anywhere like Mouser etc.

[scarceller]

Here's what I did to replace the heat controller. Super clean and simple. I only use one relay because I don't have the rear blower but the socket is in place and ready for the 2nd relay if I ever decide to use the rear blower again.

[wazzz]

Nice setup. Do you still have the ability to control the footwells with the reed switch and the overheat function ?

[eflight]

Originally Posted by wazzz

The ref. of the relay I bought is DG20-7011-35-1012. I bought 4 units. They are cheap. A couple of dollars each. You can find them anywhere like Mouser etc.

Thanks, I'll order a couple of those and see if I can fix what I have.
Should not be too hard to remove the old one and wire in a new one.

[wazzz]

Not easy to remove the old relay without damage to the PCB. I suggest you cut whatever you can of the old relay with pliers then unsolder each pin separately. This way you preserve PCB traces.
I wish I had done this with mine.

[scarceller]

No reed switch is required, look at my schematic at Pin #6 that's wired to the engine temp sensor. If that sensor activates and closes because of extreme heat engine condition it will auto activate the rear blower. My solution handles this if you implement all components as shown in the schematic.

Enjoy.

Originally Posted by wazzz

Nice setup. Do you still have the ability to control the footwells with the reed switch and the overheat function ?

[eflight]

Got the small replacement relay for the footwell blower fix.

Removed the old relay.

The hardest part of this replacement is because the new relay pinouts are different than the old one. So I had to put some pigtails on the new one to get the correct wires connected to the correct spots.

Got the relay put in and soldered up.

Now the footwell blowers work.

One other thing I did at this time was replace the old fuse panel with the new one from Adapt motorsport. I noticed the LED lights were not working, but when I touched the car and the bracket at the same time , they would light up but dim. I realized there was a ground issue.

I took a look at that bracket that holds the heater control box and the fuse panel and realized that the bracket does not have any ground line to it. It floats on rubber isolation pads for the mounting bolts and the engine wire harnesses that attaches to it uses a plastic bracket. There is no ground at all, at least mine does not have any.

And since the bracket is not grounded this means that that aluminum box around the heater control electronics is not acting as a shield. I wonder if that could be the source of all the problems people are running into.

I ran a temporary ground wire from the bracket to chassis and the LEDs on the fuse panel lit up.

So I need to run a ground line to that bracket next.

[wazzz]

Good to see the Durakool relays are working for this application. You were much faster than me. I bought mine about a year ago and they are still in their box.
May be you could secure the relay with some hot glue. That would prevent it from vibrating and moving inside the box.

As for the grounded shielding, it cannot do any harm and you can probably keep it if it helps with the fuse leds.

[scarceller]

UPDATE! Another easy solution to get the footwell blowers to run without the rear blower.

Simply take pin 4 wire and wire it to pin 5 or 6, this will power the front blowers from the rear blower output.

Pin 4 is the output for footwell blowers.
Pin 5&6 power the rear blower.

You can easily do this mod by opening the harness connector.
Remove pins 5&6 (rear blower) and tape those 2 pins off and leave them safely tucked away in the connector.
Then remove pin 4 and move it to pin 5.

In the end you have no spade in pin 4 or 6 and you rewired 4 to pin 5.

Done! You should now have heat via footwell blowers.

Study the wiring diagram provided in Post #2 of this thread.

[wazzz]

Not sure to understand. I guess you mean to do that mod inside the connector with 12 female pins, right?
But how does the main blower get power if you tape and tuck away pins 5 and 6 in the connector? As I understand it, footwells will now get power but main engine compartment blower will no longer be powered.

[pmax]

Originally Posted by eflight

...

How much current goes thru those traces ?

[wazzz]

Originally Posted by pmax

How much current goes thru those traces ?

Maybe 5 amps. They carry current for footwell blowers, but only for low and medium speeds. High speed goes through a different relay in the front luggage compartment.
This pic shows the first generation of the heater relay unit.
Second generation had wider traces for the footwell circuit, as can be seen in the following pic.

[Nick Triesch]

Or just leave the rear heater blower alone. Mine came apart but I put it back together with jb weld. Heater works great.

[LukasM]

Originally Posted by wazzz

Not sure to understand. I guess you mean to do that mod inside the connector with 12 female pins, right?
But how does the main blower get power if you tape and tuck away pins 5 and 6 in the connector? As I understand it, footwells will now get power but main engine compartment blower will no longer be powered.

This is what this whole thread is about, isn't it? How to get the front blowers working if you have backdated the heat, because of weight, cleaner looks or because the old blower stopped working and is expensive to replace.