Ventilating System no blow!, What am I missing? Options

[jsaum]

I'm trying to get everything working on my 72 914 including the fresh air blower and defroster control on the dash. I traced down the power going to the control selector lever for the three speeds, the red & white wire which does have 12 volts but it doesn't connect to anything! Am I missing a connector or a wiring harness that gets power to the blower motor from the dash? There isn't any bulbs or holders for the red and blue bezels on the control panel it seems like there should be more there!

Thanks for the help!

Jsaum

[AvalonFal]

I can tell you how a '74 works because I just went through it. Not sure if '72 is exactly the same.

I assume your fresh air motor in the box behind the gas tank is OK, not clogged and the wiring plug is connected to the box.

Power is plugged directly to the blower motor in that box, not to the dash fresh air control assembly. There should be power at the motor in the box with the key on. The only power at the dash assembly would be for lighting.

At the dash assembly, there are 2 brown ground wires - top and bottom of the assembly. One is for lights and the other is for the blower motor. Both should be connected to ground. There are 3 wire connectors on the back right side of the assembly for the white/yellow stripe wire (nearest), white green stripe (middle) and solid white (farthest). These 3 wires are the motor speed wires and are controlled by the copper arms on the assembly moving across the 3 traces when the speed lever is moved, thereby grounding the specific wire for each speed and completing its circuit. Make sure these arms and traces are clean and make good contact.

If all at the dash is connected properly and clean and there is still a problem, it might be with the motor/wiring at the box behind the fuel tank. You'll have to make sure the motor is actually working and/or not clogged with debris, and that there is the 12V at the plug.
Hope this helps a little.

Paul

[cary]

What you have in fingers is the indicator bulb holder for the blower. It needs a bulb then slide it into the socket.

There isn't any 12volt power to the switch. Switch signals are grounds, The power is on the bottom side of the blower fan in the front trunk.
You should find a matching black/blue bulb holder wire on the right side. Might be laying in the bottom tray of the dash. It has two sockets. Schematic says there's three, but both my 73 car's only have 2 bulb holders on the black/blue wire.

Hope this helps ......................

[BeatNavy]

I also JUST went through this on a '72. I agree with both Paul and Cary. If your blower motor isn't working it's likely either the ground contacts that slide across the control are covered in junk, the blower motor is clogged with leaves and other debris and has frozen, or both. To check the blower motor requires pulling the gas tank and wrestling with the fan housing to get it removed (it's connected by two bolts and the actual fan speed control cable). Then you have to open the housing and get the blower assembly out. Here's a picture of what mine looked like a couple of days ago when I did this (below).

You already have access to the controls, so you can clean those well. When I did the same thing, I could see sparks at those ground contacts when I activated the blower (although it was frozen from al the junk in it). After 30 seconds or so I could see smoke coming out of the grill on the hood which was probably one of my variable speed resistors burning up. At that point I knew I was getting power to the assembly, but I probably also lost a resistor in the process.

[DRPHIL914]

ive started the process of trying to get mine working as well. i have one speed working but not the other 2. seems it may be a resistor pack in the fan housing too, so looks like i will be pulling that soon ans well.

[jsaum]

OK thanks for all the great info it all makes sense now. I'll do some more checking on the connections and wires this weekend, looks like the gas tank will have to come out in the near future to get at the blower motor. What type of bulb is used for the connector in the dash?

Jsaum

[AvalonFal]

OK thanks for all the great info it all makes sense now. I'll do some more checking on the connections and wires this weekend, looks like the gas tank will have to come out in the near future to get at the blower motor. What type of bulb is used for the connector in the dash?

Jsaum

Wedge base. Sylvania 2721. 1.2W.

Paul

[BeatNavy]

I tore into my '72 fan housing too look at the resistors and other connections. Here's a picture of the resistor springs. When I measure the resistance across each, I got something from 4K to 8K ohms (the multimeter bounced around).



Here are the corresponding 4 posts on the outside. One, I think the upper right, is the 12v input. The others are ground connections that connect from the climate control grounds in the dash through these resistors and to the ground connection at the actual blower motor.



With the blower in the housing I was able to "bench test" it on the battery by connecting a 12v jumper to the upper right connection and then use a ground wire at the other connections. I found I had something like a slow speed when I grouned the right lower pole and a high speed when I grounded the lower left pole. Not sure how I was supposed to get a mid speed.

Then I hooked it up to the connector under the hood. Here's where the fun started. I get a little smoke when I put the climate control selector on low, a LOT of smoke when I put it on mid speed, and good, solid blower action (and no smoke) on high. Obviously I'm shorting something to cause the smoke. I'm not sure what gives. Need to think this through some more. Smoke near the fuel tank is not an ideal feature.

[jsaum]

Well I made some progress but no sucess in getting the thing to work. I cleaned the contacts and confirmed they have good grounds. I also picked up a bulb and got the blue blower indicator light on the right side of the panel working it comes on when you slide the lever. I still can't find the wire or bulb holder for the red light on the left side of the panel. I pulled the panel out as far as I could and also took the instrument panel and gauges loose so I could look behind them for any wayward wire but found nothing. The wiring diagram for my 72 shows item 54 as a relay for fresh air fan, can anyone tell where it's located?

[etcmss]

relay is on the main fuse panel.
http://bowlsby.net/914/Classic/zTN_Elect_R...inFusepanel.jpg
are you sure you have good contact to allow the fan to run? recently had this trouble and although the lights worked the fan was not getting power enough to operate. Had to clean the electrical slide fingers more and it finally cleared up.
Some models had a screen at the hood grill to prevent this debris from getting into the fan---is yours there? this picture was from a 71.
the left side light socket may be loose and laying on the lower dash pad, but its likely there.
Gary

[BeatNavy]

I tore into my '72 fan housing too look at the resistors and other connections. Here's a picture of the resistor springs. When I measure the resistance across each, I got something from 4K to 8K ohms (the multimeter bounced around).



Here are the corresponding 4 posts on the outside. One, I think the upper right, is the 12v input. The others are ground connections that connect from the climate control grounds in the dash through these resistors and to the ground connection at the actual blower motor.



With the blower in the housing I was able to "bench test" it on the battery by connecting a 12v jumper to the upper right connection and then use a ground wire at the other connections. I found I had something like a slow speed when I grouned the right lower pole and a high speed when I grounded the lower left pole. Not sure how I was supposed to get a mid speed.

Then I hooked it up to the connector under the hood. Here's where the fun started. I get a little smoke when I put the climate control selector on low, a LOT of smoke when I put it on mid speed, and good, solid blower action (and no smoke) on high. Obviously I'm shorting something to cause the smoke. I'm not sure what gives. Need to think this through some more. Smoke near the fuel tank is not an ideal feature.

So I did some more testing, and it appears that I'm only actually getting smoke on the low setting. By explanation, of the four pictures in the post above, the upper right pole is the power input. The upper left is the low setting ground. The lower one opposite, just under the power pole, is medium. And the lower left one is high. At the connector in the trunk, the power line is always hot, and moving the fan speed select switch grounds one of the three poles - upper left for slow, lower right for mid, and lower left for high speed.

Clay Perrine helped me figure some of this out, like the fact that I guess the low speed actually grounds through both of the resistors while the mid only grounds through the bottom. The fan moving helps cool the resistors. Right now I'm getting smoke on the low setting and the fan is not moving. I can see that the fan may not be lubricated or moving freely enough to move on the low setting. So do I most like a) have a short there that's causing the smoke, or b) is it just the resistor(s) overheating without any fan action to cool them?

I'm ok without any low fan if I have mid and high at this point, so if I'm risking anything I can just snip the low resistor, I suppose.

[jsaum]

Does anyone have a picture of the wiring harness for the left bulb holder on the ventilation control panel? I've been all over the underside of the dash and instrument panel and I can't find the black & blue wire or any type of holder. I've ran my hand on the underside of the dash pad from one end to the other and found nothing. I've also used a mirror and flash light trying to get a better look. Does the red indicator light come on with the intsrument panel lights? Or is it also activated by the control levers?

Thanks,

Jsaum

[AvalonFal]

Does anyone have a picture of the wiring harness for the left bulb holder on the ventilation control panel? I've been all over the underside of the dash and instrument panel and I can't find the black & blue wire or any type of holder. I've ran my hand on the underside of the dash pad from one end to the other and found nothing. I've also used a mirror and flash light trying to get a better look. Does the red indicator light come on with the intsrument panel lights? Or is it also activated by the control levers?

Thanks,

Jsaum

I don't think there ever was an operating red light on the fresh air assembly from the factory, so you're not gonna find that blue/black wire you're looking for, unless it was added by a PO. My '74 doesn't even have the red light indicator (I think it stopped after '72MY.)

Here's an old thread about ADDING a red light.

Fresh Air Light

Paul

[jsaum]

OK that explains why I can't find it! I checked out the thread it does kind of look cool to have them both working!

Thanks!

[etcmss]

attached wiring drawing for 72-73.
the lights aren't clear for left bulb and right bulb but appears to be 2 different ones.

[jsaum]

attached wiring drawing for 72-73.
the lights aren't clear for left bulb and right bulb but appears to be 2 different ones.

Is it possible to get a full version of this wiring diagram? This is better than any of the ones I have!

[clapeza]

attached wiring drawing for 72-73.
the lights aren't clear for left bulb and right bulb but appears to be 2 different ones.

Is it possible to get a full version of this wiring diagram? This is better than any of the ones I have!

http://www.colorwiringdiagrams.com/porsche.htm

11"x17", printed on both sides and laminated.

Just got mine! Love it!

[jsaum]

I made some progress at the fuse box figured out which relay is used for the fresh air blower and confirmed that the relay and 12 volts are working correctly. I was able to get 12 volts reading on wire #9 coming out of the fuse box on fuse #12.

Once the ignition key is turned on power is sent through the relay giving power to the blower and when the control level is actuated grounding the circuit it should come on. I used a jumper to the white and green wire to ground and got nothing. Here are pictures of the relay and wire. It looks like I'll havbe to pull the blower.

[DRPHIL914]

so (jsaum) what did you find out on this? was the issue a wiring issue or the resistor at the fan? or just a dirty fan?