Carrera - Removing Engine Compartment Heater Blower

[aj88cab]

Originally Posted by shadowjack1

Yes I do get 12 v (11.85 v now) I'm thinking that the relay is faulty and not sending enough voltage to run the motor. If I had a bad ground, the plug at the fan would not see 12v.

Not necessarily, it's an amperage thing. If the ground is not solid you can get the voltage reading, but it may not provide enough current to run the motor. On the other hand it could be the same issue (corroded contact) at the relay too. The easiest (only) way to check the relay is to switch it out with a known good one to see. With the fan installed you can check the power circuit without the relay by pulling the relay and jumping with a wire between pins 7/8 (power from fuse) and pins 5/6 (to blower).

Relay schematic -The red line is just a correction to the diagram, not the suggested jumper location.

[redridge]

Excellent thread as I'm thinking of backdating my heat system.

To answer someone's question.... How does the rear blower cool down an engine? Well, when I was pulling out the blower and it's piping... The piping is actually part of the engine shroud. When the blower turns on via a temp hi switch, it helps the engine fan pull the heat out of the engine shroud ( since the piping is part of the shroud) and diverts it via heat exchanger.

[redridge]

Another point.... The coil around the reed switch (glass tube). Someone also asked in another thread... Why is it there? It is a feedback circuit that tells the footwell blowers that the rear blower is running and pulling enough air (proper current draw). The amount of coil around the switch is the amount needed to create a magnetic field to close the switch at normal blower load.

To my next point, the footwell blowers are designed to work with the rear blowers.... Without the rear blowers you will be over working the footwell blowers since they are pulling the air without the aid of the rear blowers.

Has anyone fried their footwell blower doing the rear blower delete? Thanks for the feedback...

[tazzieman]

Originally Posted by redridge

Excellent thread as I'm thinking of backdating my heat system.

To answer someone's question.... How does the rear blower cool down an engine? Well, when I was pulling out the blower and it's piping... The piping is actually part of the engine shroud. When the blower turns on via a temp hi switch, it helps the engine fan pull the heat out of the engine shroud ( since the piping is part of the shroud) and diverts it via heat exchanger.

So I have an SC , when it's cold outside my engine stays cool , but when I turn on the blower I get some free engine heat...OK for the cabin/screen.
On a really hot day though when the engine temp is creeping up , I don't want the engine blower on to cool my engine! Hmm.

I can't believe the system was that badly engineered, and maybe the system is designed to work as a whole. Or perhaps it was a case of trying to keep all possible customers happy.

Though I like the idea of the delete , like others I wonder about the overall effect. I suppose I should just pull it all out and see how if the simplified system works satisfactorily (on cold days).

[aj88cab]

Originally Posted by redridge

Another point.... The coil around the reed switch (glass tube). Someone also asked in another thread... Why is it there? It is a feedback circuit that tells the footwell blowers that the rear blower is running and pulling enough air (proper current draw). The amount of coil around the switch is the amount needed to create a magnetic field to close the switch at normal blower load.

To my next point, the footwell blowers are designed to work with the rear blowers.... Without the rear blowers you will be over working the footwell blowers since they are pulling the air without the aid of the rear blowers.

Has anyone fried their footwell blower doing the rear blower delete? Thanks for the feedback...

You are correct....The reed switch is there so the FW blowers only run if the engine blower is running.

The FW blowers would not really be overworked as the the engine cooling fan produces plenty of pressure to force air thru the heat exchangers without the rear blower fan. The FW blowers fry for many reasons, but this is not one You do have to be careful with how you accomplish the rear blower delete, so that the FW blowers do not run all the time, as is the case with some of the control relay jumper configurations discussed.

[aj88cab]

Originally Posted by tazzieman

So I have an SC , when it's cold outside my engine stays cool , but when I turn on the blower I get some free engine heat...OK for the cabin/screen.
On a really hot day though when the engine temp is creeping up , I don't want the engine blower on to cool my engine! Hmm.

I can't believe the system was that badly engineered, and maybe the system is designed to work as a whole. Or perhaps it was a case of trying to keep all possible customers happy.

Though I like the idea of the delete , like others I wonder about the overall effect. I suppose I should just pull it all out and see how if the simplified system works satisfactorily (on cold days).

Someone correct me if wrong, but I don't believe you have the auxillary cooling feature in your SC. In the Carreras the auxillary cooling function of the engine blower fan is controlled by a temp switch at the oil breather cover, and, by a signal from the speedometer. So the auxillary cooling feature only functions when the car is stationary or moving very slow. In any case (SC or Carrera), if your driving with the heat lever OFF, you are probably not running the engine blower fan.

BTW - I have never seen this auxillary cooling function occur on my car, so I don't know what the temp setting for the temp switch is but it must be pretty high.

[rtu0894]

Awesome thread! thanks to everyone. learned a lot. What I did learn is that mostly everything works as it should, Trouble shot all blowers independently, red handle(micro) switches, reed switch, and proper continuity to pin 9 in both lever positions. everything works. first off, the problem is the engine comp. blower doesn't work, actually intermittent, seldom at best. I read all the threads, most of which deal with the reed switch. I took the relay cover off, and when I manually press the large relay, everything works as it should, reed switch, small relay and all blowers. Triple checked pin 9 to ground. Looking closely at the circuit board, I can not seem to locate the actual tiny coil wires for the large relay coil to the board. must be obscurely done exactly underneath. Can anyone point out these solder points on the back side of the board? Thanks a bunch!

[scarceller]

Pin #9 actually gets it's ground through the Starter solenoid coil winding, they do this so that the heat blowers shut off if the key is in 'START' mode. So if you put a Volt meter between ground and Pin 9 you should read 0 volts but while key in 'START' mode it will read 12vdc.

Likewise: with key off or any other position but 'START' you place meter between pin 9 and a good 12vdc source (like one of the 3 rear fuses) you will read 12vdc but while cranking you'll read 0vdc.

It could be something has occurred to pin 9 wiring and it's now not getting ground via the starter solenoid?

For what it's worth I tossed the complicated heat controller in favor of 2 simple relays (see earlier posts) this solution works great and is far simpler.

[rtu0894]

Yeah thanks, I also tried a jumper from a known frame ground to the solder point for pin 9 on the board, with the cover off, effectively by-passing everything. still nothing. I found a new one for $370. I like to keep electrical things original but screw it. already trying to find some relays I have lying around for the mod. Gonna go with the diode one as well. thanks

[scarceller]

First, buy relays with the sockets and pigtail wiring.
Then you have 2 choices when wiring the relays:
1) Cut the factory harness and splice in the pigtails (I did this) then solder all wires and complete with shrink tubing.
2) Hack up the factory controller by removing the board from it then simply wire the pigtails to the controller pins. Someone else on this thread did this and actually placed the relays inside the tin of the original controller. Kind of clever, keeps it looking stock.

Best of luck.

[rtu0894]

I'm starting to gather parts for the two relays mounted in the original tin approach. On this Bosch relay I already had, can anyone explain the two diodes factory installed? The two outside pins are the coil leads and they attach to the common post...

[rtu0894]

Another successful conversion. Thanks again for the awesome thread!

[NYNick]

Old thread, new question.
If my relay was replaced, How do I tell if it's the old style relay or the new style relay? The part numbers are supposedly the same.

Also, has anyone done the jumper per Post #95? My symptoms are the same as Tailwinds are/were.

I hesitate to tackle this on an expensive relay without being certain it's going to work.

Thanks

Nick

[aj88cab]

This is the updated jumper configuration I helped Tailwinds with a few years back. I did this configuration for a fellow Carrera owner recently and his heat is working fine. FW blowers come on with red levers up and don't run all the time (with levers down) as with other jumper schemes.

Close-up of reed post & pin connection point.


Cheers,
Andrew

[NYNick]

Wow, those are awesome pictures and a great and simple fix.
One more question: how does one open up the relay without mangling the whole thing?

Thanks!

Nick

[aj88cab]

I use a small flat head screwdriver and pry the lip of the aluminum housing to remove the internals. I have found that gently pushing the screw driver tip around the corners helps to get the plastic connector plate to release. Pay attention to the orientation of the connector and housing, and the location of the insulator card inside the housing for reassembly.

[NYNick]

Thanks Andrew.

[krshome]

I have two questions on doing the heat back-date on a 88 Carrera. First with the removal of the blower fan you loose the additional cooling if the engine compartment hits 180 deg. When the aux fan comes on, does it really do that much for cooling? (I don't think mine has ever come on) Second by removing the heater blower fan at the engine and doing the relay mod, will this affect the auxiliary oil cooler fan up front under the passenger side fender?

[Jaskas]

I dont think that the heater blower does that much cooling to the engine after shutdown. Its not connected in any way to the oil cooler fan either.

I did infact remove all the plumbing from the engine to the heat exchangers, but left the hoses from the heat exchanger to the car + the footwell blowers. This generates plenty heat, even this morning there was -5 celcius and the car warmed up fast. ( You have to have the footwell blowers sucking warm air to the cabin)

Here is the hoses that i removed:


I the pic below you can see also the hoses from heatexchanger to car.


I the pic below you can see also the hoses from heatexchanger to car.

[krshome]

HELP ME!!!!! Ok when I started this Back date back project everything worked fine, I removed engine blower fan and did the mod to the relay. Nothing! No footwell fan at all, so i went back and did the updated mod since I have a 88. Nothing no footwell fan. So I put everything back to stock undid the mod to the relay put the heater fan back in the engine compartment. Now the rear blower works but the footwell blowers do not. I checked for power at the footwell nothing. The rear fan is working in the engine compartment. I checked the fuses at each blower, they are ok. The fuses by the relay are ok. Am I missing any? What did I do to loose all power to the footwell blowers????????