footwell heaters

[m110]

Originally Posted by 911M491

Thanks m110. What isn't clear to me with this mod is can i still use the engine blower?

I don't totally understand because the goal of the mod is to eliminate the engine blower and rely on the footwell blowers only.

[911M491]

That is the issue. My engine blower works and is providing heat. The fw blowers work with 12v. I discovered both reed switch and secondary relay were not working. I replaced the secondary relay with a radio Shack relay. So I'm looking for a work around the reed switch that won't run the fw blowers continuously even with the switch at 0.

[911M491]

Just to be clear. I don't want to eliminate my engine blower. I just want my fw blowers to work when I turn them on.

[aj88cab]

There are a couple items being discussed that possibly need clarification.

The original reed switch jumper mod was accomplished with a jumper wire across the reed switch circuit. This completed the control circuit for the FW relay coil and ran the FW blowers. The problem was that this control circuit power is always hot and independent of the levers or any switch. The result was that the FW blowers ran whenever the engine was on, even when the heater levers were down (OFF). The modified mod, uses the power from the engine blower circuit to operate the FW relay coil so the FW blowers only turn on when the engine blower is turned on. Some discussions have indicated that this is only applicable to "later" relays, but I am not sure that is correct. I believe the "always hot" reed switch control power is the same for all models.

The question of the FW blowers running on the "0" setting if the heater levers are up (ON) is not an issue, is it designed that way. There are a couple of reason for this I believe. One is that there is too much heat running through the system to not have the FW blower fan "moving air" when the heater levers are ON. And also, the FW fans are "in-line" and block the flow of hot air if they are not running. So the "0" & "1" setting are designed to run at the same (slow) speed whenever the heater levers are up (even just a little).

[911M491]

Thanks for the reply aj88cab.

After jumping the reed switch, my fw blowers ran all the time even with the levers down with three speeds 0/1, 2 and 3. I jumped the two solid wire ends before and after the coil.

Is it correct that this is the mod for eliminating the engine blower and only using the fw blowers? Is there a different mod that still uses the engine blower with the levers and the fw blowers that when the engine blower is on (levers up) the fw blower will run at what ever switch setting (0&1 slow, 2 mid and 3 high)? Is this the mod that jumps on the circuit side or another jump? Thanks for your help with this.

[911M491]

Here are a few photos of the radio shack relay.

[aj88cab]

Originally Posted by 911M491

After jumping the reed switch, my fw blowers ran all the time even with the levers down with three speeds 0/1, 2 and 3. I jumped the two solid wire ends before and after the coil.

That is the issue with just jumping across the reed switch. The FW blowers run continuously regardless of the position of the levers.

Originally Posted by 911M491

Is it correct that this is the mod for eliminating the engine blower and only using the fw blowers? Is there a different mod that still uses the engine blower with the levers and the fw blowers that when the engine blower is on (levers up) the fw blower will run at what ever switch setting (0&1 slow, 2 mid and 3 high)? Is this the mod that jumps on the circuit side or another jump? Thanks for your help with this.

This is the mod you need to do to NOT have the FW blowers run all the time. This would work to run the FW blowers whether you have the Engine blower or not, and the FW blowers would turn off when the levers are down.

http://forums.pelicanparts.com/porsche-911-technical-forum/388445-carrera-removing-engine-compartment-heater-blower-6.html#post7669605

You mentioned that your FW relay was bad and you replaced it, so I don't know how that will fit into the scheme. The picture of your relay replacement didn't post, but if you use Pin 5 to power the coil of the replacement relay I think it should work.

And just to complicate things If you are using replacement relays you might want to abandon the original control circuit board and just use the method described in the posts by scarceller earlier in the above thread...

[86 911 Targa]

From another member.

[crownarch]

The above fix posted by 86 911 Targa is the same fix I did on my 87' and it works perfect. I did not use the diode nor pin 10 wiring. If I pull up my levers the engine blower works and to activate the footwells I merely pull levers further up. Also, when I run my A/C I activate the engine blower which provides more air flow thru the engine lid grill and drops my engine temp when idling. I suggest doing this fix and then look for a used Heater relay which can be picked up for 70-100 bucks as a backup or should you decide to sell the car.

[911M491]

This is an awesome confirmation about the "Mod/Mod" Heater Controller (my modual is date stamped '87) for late model Carreras (87 -89) with manual heating systems . I'll look at the thread to id the exact aftermarket relays to replace the entire control modual pcb board. I think it is important to reiterate that this is for those who will use their original working engine blower or with a "Wavey mod" like mine and use their FW blowers. I don't know why my jpegs won't upload. Thanks for your help.