No voltage 2nd stage rear window defogger relay.

[bigpino]

I'm about to wire my rear window defogger, but noticed that the relay is not giving any voltage on the second stage connection (see pin 3 in diagram below). In the electrical diagram one can see that there exists an "solid state" unit.

I think this is the problem, but what is it for? And how can I get it to work? I need this since I'm going to use these connections to turn on two separate functions. (defogger and motor compartment blower (got no heater controller??)).

[86 911 Targa]

I have been flogging this issue for about a year!

Having bought two replacement relays with the same results
as you are having, I finally contacted the folks @ Hella.

The issue is that relay #2 on the PC board is not being activated
by the solid state circuitry.

My best guess is that relay #2 is on a time delay, or cycle profile
by the circuitry in order to prevent rear window fracture.

As you can see by the attached diagram, all voltages and ground
are present.

Additionally I verified element(s) continuity.

Resistor R1 is most probably a factory adjusted setting for a
time constant circuit.

Email me and I'll go into the details with you.

[bigpino]

Ah, that makes sense. Thanks for your response and offer gerry50, but I think I can work it out from here on.

I was going to tie all defogger elements together, but that doesnt seem to be too sensible with the potential cracking and all. Than I have to find another way to activate the engine compartment blower, since I got no heater controller (relay). Any suggestions?

[bigpino]

Oh, im sorry. I meant gerry 40 off course. Yes, I'm wondering if the separate staging is really necessary? Although, I dont want to take the risks in the winter (with normal temperature I think it makes no difference).

I got a 3.2 and looking at my motronic EPROM it should be around 84.

[86 911 Targa]

The two stage is indeed necessary as the center element will not adequately defog your rear window especially if you have a Targa, and live in a very cold climate.

The only time we use ours is on winter trips to the mountains.

However, having friends at, and visited the factory on several accassions, I assure you that the "Porsche Coats" are very thorough folks.

They put that two stage in for a reason.

The earlier 911 (2.7's) had a two position switch on the dash board which,
had time out problems.

Lots of fractured rear windows.

[bigpino]

Im a believer myself when it comes to true purpose of components in Porsches. I have a two position pull switch too (besides off), but it is not a targa. However, I will wire it in the correct manner in the near future.

I got a workshop manual (84-89). I dont think its a Bentley.

The heater controller relay and its socket is completely absent, at least the 12 pins version. So is the middle/armrest console. I discovered a bundle of wires and a round relay (5 pins) in the engine compartment fuse box. I think it is and older blower system or so:

bundle towards relay:
red / white (one of the pins of relay, always hot 25A fuse 2 ??)
red / black (one of the pins of relay, always hot 16A fuse 1 ??)
yellow or white / green (bundled, but not connected to relay)

bundle from the relay (only 4 wires)
red / white
red / black
yellow / black (to connector of the blower with brown as ground)
yellow

Questions remain:
- which of the wires is the control wire
- to what should this wire be connected (dashboard temperature slider or something ???)

[bigpino]

How about the fresh air blower? I took it out to oil it and after installing it again it blows maximum in all positions. The diagram shows some switches to shunt the resistors. What is that all about?

[dshepp806]

Bad transistor, probably. just check all of the components values/integrity,...replace as necc. Looks to be quite the simplest of circuits.......have you checked (measured) them?

Doyle

[bigpino]

dshepp806, if you refer to the fresh air blower (luggage compartment) then there are no transistors involved. The dashboard slider got some slide contacts and the blower got some resistors as you can see in diagram above.

However, what are those switches parallel to the resistors. They seem controlled by nothing??? In my case they are all short circuiting the resistors, since all positions of the slider result in maximum blow.

[bigpino]

ok, the whole wiring for the engine compartment heater blower works. However, I still havent figure out what will switch it on (yellow wire).

I read something about the mid 'console' heater levers (red) pulling up will connect the blower as well. I have the levers, but does anybody know where the switch is?

[ClickClickBoom]

Originally Posted by bigpino

ok, the whole wiring for the engine compartment heater blower works. However, I still havent figure out what will switch it on (yellow wire).

I read something about the mid 'console' heater levers (red) pulling up will connect the blower as well. I have the levers, but does anybody know where the switch is?

Hello,
I am on the same rampage, my engine compartment blower turns on when turn the key on, and will not shut off until I turn the key to the off position. Relay logic? missing switch somewhere?
eric

[bigpino]

Eric, does pushing down the heater flap levers turn off the blower? Do you have a 5pins round relay or a 12pins box relay? In the meanwhile you can pull the blower relay just to shut it up.

I had 2 yellow wires connecting each other near the handbrake lever (going into the beam where the shift couple is). Between the connection a switch should be placed, but I got no idea where that switch should be. Unless, one should have a 'climate' control in the mid console.

[ClickClickBoom]

Originally Posted by bigpino

ClickClickBoom (weird nickname), does pushing down the heater flap levers turn off the blower? Do you have a 5pins round relay or a 12pins box relay? In the meanwhile you can pull the blower relay just to shut it up.

I had 2 yellow wires connecting each other near the handbrake lever (going to the beam where the shift couple is). Between the connection a switch should be placed, but I got no idea where that switch should be. Unless, one should have a 'climate' control in the mid console.

ClickClickBoom, comes from the Deer Hunter movie, ala russian roulette, put one in the chamber, spin the cylinder, place against head and pull trigger, more than once if you are crazy! But I digress, I will pull my hand brake lever and fish around in there. Going out now, back in a minute or hour.
eric
P.S. 5 pin round

[bigpino]

Got a 5pins as well. What I can remember I wired it as follows

bundle from the relay (only 4 wires)
pin 30 - red / white (alway hot fuse 2 25A engine compartment fuse box)
pin 85 - red / black (switched hot, I have search for one in engine compartment and added a fuse)
pin 86 - yellow (if grounded than blower will turn on, still dont know where the switch is)
pin 87 - yellow / black (to connector of the blower with brown as ground)
pin 87a - not connected

[ClickClickBoom]

Hey,
I pulled the parking brake, no heater wires or switch. Went fishing under the dash, on the 3 lever climate control there is a 12V yellow with red stripe that is hot when the switch is on and dead when the red lever is moved to the right side of the car.
FWIW
eric

[dshepp806]

Originally Posted by bigpino

dshepp806, if you refer to the fresh air blower (luggage compartment) then there are no transistors involved. The dashboard slider got some slide contacts and the blower got some resistors as you can see in diagram above.

However, what are those switches parallel to the resistors. They seem controlled by nothing??? In my case they are all short circuiting the resistors, since all positions of the slider result in maximum blow.

Sorry,..I think I was following the first post mentioning no output for the center elements......

Doyle

[dshepp806]

Originally Posted by bigpino

dshepp806, if you refer to the fresh air blower (luggage compartment) then there are no transistors involved. The dashboard slider got some slide contacts and the blower got some resistors as you can see in diagram above.

However, what are those switches parallel to the resistors. They seem controlled by nothing??? In my case they are all short circuiting the resistors, since all positions of the slider result in maximum blow.

As to the switches, not sure. Formally (schematically), it would appear to be duty cycle-related or time based,..or it's a poor illustration of something thermally controlled (although that's not quite the schematic rep for such a device.

Time to break out those (blower) schematics,...let's see..........

Doyle

[bigpino]

ok, sorry for that. Fortunately, the yellow/red is a candidate. I will have a look later for that. If it's the same I have to rewire pin 85 and 86.

In your case, you should remove the relay and see if terminal 85 or 86 is 'connected' by that yellow/red (put e.g. a lamp on). If it does then the complimentary terminal should --I guess-- be permanent ground. If all checks then I guess your relay is stuck (maybe should check that first).

[ClickClickBoom]

Originally Posted by bigpino

If all checks then I guess your relay is stuck (maybe should check that first).

I swapped the horn relay, same-same, blower on all the time.
I am looking at the Porsche "flow diagrams" and looking for the actual switching signal.
later
eric

[bigpino]

Ok, Doyle. That makes more sense. In the meanwhile it gives 12V so I connected center element to 1st stage and upper and lower elements to the 2nd stage. I haven't checked what the exact interval is of the 2nd stage, but it is on right at moment I turn on the 2nd stage. Any idea what the interval is. Is it a matter of seconds or minutes?