Really appreciate all this info! As it happens, my current winter project is to sort out the heating setup of my 84 as it ain't working. I have the automatic setup. The previous owner disabled the a/c by removing parts of it, such as the rear condenser and the compressor. Not sure if this has anything to do with the heating part of it - all I know is that it doesn't work.

I have the Haynes 911 manual, but that is pretty useless. Thanks to this thread I am getting somewhere! In particular, pictures, diagrams are very useful. :)

For what it's worth.

Here is some stuff I've gathered. Mainly AutoHeat info but much of it applies to Manual. Contribute if you can & I'll post it - especially the troubleshooter part.

AutoHeat

Ian

Thanks for the link, Ian. I intend to invest the better part of this Friday on trying to understand the intricacies of my Carrara's auto-heat system and will certainly report out on it.

I think I might have found the problem. Please jump in if not correct:

I decided to pull fuse 2 in the luggage compartment. That kill power to pin 30 on the relay but pin 85 still had power. My understanding was that pin 85 is not supposed to have power. I looked at the Bentley diagram and it looks like the dial switch grounds 85 when on position 3 in order for the relay to work. Which cann't happen because 85 has power.

Current possible solution:
Take relay plug out, rewire 85 to the dial switch. Comments are welcomed. I am not thrilled about doing this since the current wiring looks very stock.



Ian, thanks for your site. I found it useful. I had already looked it though.

Ron, thanks for the diagrams. the relay is on position one counting from the windshield
I have swapped the relay with the other ones and still the same results.
I still have the rear blower in the engine bay

Instead of the relay socket wiring, check the connections at the dial switch at the console. It seems a more likely place for a mis-wire to occur.

I did that. I actually disconnected the white/Green wire from the dial switch and the wire still had power. From looking at this diagrams pin 85 should be ground. Correct?

That would be my interpretation. Pin 85 is ground with rotary switch at #3 position.

But....If the heater levers are up the wt/grn wire would have power. Starting at pin 4 on the controller to connection point 3 on the rotary switch to pin 86 on the relay then thru the coil of the relay to pin 85 and finally the wt/grn wire. Pin 4 on the controller provides the blower power for settings 1 & 2 and is hot with the levers up. The voltage at the wt/grn wire goes to ground thru the #3 switch setting.

I'm beginning to confuse myself.....but from the info so far it looks like either the #3 setting on the switch is not closing or the path from the switch to ground is not made.

I am starting to get confused as well. :confused:

Putting aside whether the switch at position #3 grounds the wt/grn wire or not ( I disconnected the wt/grn wire for testing)

When the rotary switch is at position #3 the wt/grn wire should no longer have power. Right? am I reading the Bentley diagram correctly? If that is the case then the problem narrows down to why wt/grn or pin 85 still has power when the switch is a position 3

Based on the wiring diagrams the wt/grn wire will have power as long as the heater levers are up. Putting the rotary switch to setting #3 completes the circuit to ground allowing the power to "flow", in this case it flows thru the coil of the front relay. This flow is required to energize the coil, which closes the relay contacts, and provides full power to the footwell blowers.

If you have power at the end connector of the wt/grn wire and the slow speeds are working then it appears that everything is working up to that point in the system. This seems to leave the rotary switch #3 contacts or the final ground path from the #3 contact to the ground point in question.

Have you checked the continuity thru the #3 switch and from the switch to ground. Everything else will work without this ground path. But the front relay will not energize without it.

The diagram from the web link you found will illustrate this better I think. The Bentley diagram does not show the switch connections and path for the manual controls. The pin and connector reference numbers I have been using are from the web link diagram.

Try this to test the front relay circuit....With the heater levers up, take the end of the wt/grn wire and touch it to a bolt or bare metal part of the car body. This should complete the path to ground and the footwell blowers should come on at full speed.

If not I am stumped......

Andrew

Andrew,
I tried grounding the wt/grn wire while the dial switch was at position 3. Unfortunetly, the wire started to heat up and the fans did not come at full blast. I only held the connection for a few seconds. I really thank you for all your help. It is so frustrating being so close

The bentley diagram shows a diode on the center leg of the fan speed resistor. If this diode is bad it may causing a short circuit. That might be why the wire got hot. Such a short circuit could have previously fried the #3 contact in the rotary switch or the wire to the ground point. Did you ever check the continuity thru the switch? I can't think of anything else. I don't know if that diode is part of the resistor or a separate item. You could disconnect all the 3 wires to the resistor which will remove the diode from the circuit, and then try touching the wt/grn wire to ground again but that is you call considering the potential for damage with a short.

continuity through the switch was fine. I try it without the resistor tomorrow. Thanks again.

This thread motivated me to play with my heat controls a little more last night. The car is a 78. The blower in the engine compartment wasn't working... took off the left side fuse/relay cover and found that the bottom fuse was missing. I turned the ignition on and found that I had power to one side of the fuse, and then found that pulling up the levers between the seats gave the other side of the fuse ground, or continuity. I looked at the inside of the plastic panel cover and it said that the top fuse was for the rear window defrost, the center fuse was for the blower (????) and that the bottom fuse was for the Sportomatic (???) The top and center fuses were there, but the lower one was not and thats what got the blower working. It calls for 25A fuses on the top two, and a 5A fuse on the bottom, but I don't know if I trust that cover diagram since it says the fuses are for different things. It currently has two 25A fuses on the top two, and I put an 8A fuse on the bottom for the blower as thats all it seemed to control. I'll pick up a 5A fuse at work today (didn't have one at home) and see if it stays intact.

Anyways, now that the blower is running I don't feel hardly any heat/flow coming out the vents. I have good flow at speed and when the engine is revved because of the fan... so is that rear blower really worth a crap? The car originally had A/C, but some of it (mainly in the engine bay) has been removed and I haven't gotten the front blower to work yet. Will this improve things? I'm slowly figuring out the ventilation system.

With the red levers up you will have 12 volts going to pin 86 of the front relay. It will travel thru the relay coil and will be sitting on pin 85 waiting for a connection to ground. When the switch is turned to position 3 it gets its ground connection.

console/switch not working. Solution found
 

I fixed it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! :)

So there were two problems:

1st problem:
the switch at position 3 did not always get continuity. Thanks Andrew for this idea.


2nd Problem:
the relay was bad.

Something I learned today is to test individual items at the time. It just happend that when I swapped the relays the switch did not get continuity hence swapping the relays made no difference.
Also when I simply tried grounding the white/green wire it did not work because the relay was bad.

Since Andrew kept asking about continuity I decided to check it again. Sure enough after switching to speed 3 I did not always get continuity. I simply bent the relay strip and that fixed that problem. Then I decided to swap out the relay and wow!!!! what a difference! It reallly blows some air now!

Thanks to everyone specially to Andrew and Ron.

Speeds 2 and 3 make huge difference. The only down side is that one of my footblowers squeaks at high speeds. Has anyone know if I can lubricate it?

Mauricio,

That's great news. Glad I could help.

As for the squeeking. A few drops of light oil on the shafts might help. However the problem might be the very small clearance between the fan cage and the housing. See my discussion above regarding the fused plastic. Especially when the weather is colder. If you can move the fan cage on the shaft you can get a little more clearance, but I could not get mine to move for fear of braking the fan cage.

But for now I say forgetaboutit....... you deserve to go for a nice spirited drive on some local twisties as a reward for you perseverance.

Enjoy the ride,
Andrew