rentadate

so I have a small problem with the heat. It recently started being really cold out here. I find that I have heat, but is it supposed to be blowing really weak? It seems to be more just leaking the heat into the interior, but doesn't have any real power like my brother's BMW. There in turn I can't get adeqate defrost/defog on my windshield. Any idea on what is wrong and how to go about fixing it?

I also have a problem, when the car is idling the lights are at more of a dim level. When i hit the gas the car's lights get brighter. I'm curious as to what I need to fix that? A new alternator? A voltage regulator? Any ideas?

Thanks ahead for all the input. This forum saves me a lot of time and trouble.

-nick

jdogporsche

Hey Nick,

What year 911 do you have? Do you have a blower? Can you hear your blower fan when you move the top lever on your ventilation panel to the right most position? Have you ever heard it? Does the heat just leak in through the dash defrost vents by the windshield? If your blower is not working, you will get heat as you drive down the road, but like you said, it would be blowing in rather weakly. Give us some more details :-)

Droops83

First I am wondering what year 911 you have. If it is an early car, it has no blower motor in the engine compartment at all, these didn't appear until the later 2.7s. If you do have a blower, jdog has a good suggestion in checking that it works. In either case check the heater hoses from the heat exchangers and make sure the cables are OK and the lever(s) open the flaps properly. I must state, however, even with the blower motor working perfectly, all hoses intact, etc, the heating/defrost on any air-cooled 911 is gonna be marginal at best, definitely not as good as in your brother's BMW.

As for your electrical question, I am again wondering if you have an early car or not. On the early cars (thru '74), the alternator does not put out much at low RPMs, even if it is working properly. For '75 (I believe), the same year the engine compartment got the heater blower motor, the alternator was upgraded. The 911SC did not get an internal voltage regulator till '82. In any case, put a voltmeter across your battery terminals while the car is running. On an early car I wouldn't necessarily be worried if it's not much above battery voltage at idle but I'd defnitely want to see it at least 13.5V at 2,000 RPM regardless of the year. Try it again with the headlights and some accessories on and make sure the voltage doesn't drop too much. If you are in doubt, have a shop test your charging system; they can load up the system and see the exact amperage the alternator is putting out. Good luck.

---

Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA

jdogporsche

Well, the reason I was responding so quickly is that I am having the same problem to some degree. I have a 77 911 (Euro). My blower used to work, up until about a week ago (coincidentally stopped working right when I needed it!), but is not blowing now. I checked my fuses which all appear to be just fine. Checked my levers and as I move them left or right, they are moving too. The top right most lever is the one that would turn the blower on when put in the right most position. From what I understand that is an electical switch? Is there any wiring I should be checking or anything else that would give me some clue as to the blower failure? Thanks in advance!

theiceman

Did you read the other posts Jeremy ? I sent you a reply , I think you are talking about the fresh air blower and you can get to it by taking off the cardboard protector in the front cargo area, you should then ba able to get a meter on the blower.

jdogporsche

Yes I did read it, but to be honest, I did not really follow you. When I got back today from lunch and speaking with James, I was inspired and opened up my 101 projects book. After reading what Wayne had to say about blower failure, I understand now and should be able to troubleshoot it. Last weekend I pulled the cardboard protector off in the front cargo area, but was not really sure where to go from there. Here is one question for you though. In the picture (not my car, just a pic I found online) I have attached...where the arrow is pointing to the control levers. Is the top most lever (exactly where I am pointing in the picture), an electical switch? When I move this lever to the right or left, should I see things moving at the blower motor? I ask this because I can see things moving at the blower motor when I move all the levers from left to right except the upper right most lever. Also, from reading Wayne's book, do the levers between the seats (which I also point to) work in any capacity as an electrical switch? I understand that when I pull the levers in between the seats, the air turns warm due to the air flowing from the heat exchangers, but Wayne mentions when pulling the switch to turn on the blower motor, the relay should make a slight clicking noise. I just want to make sure I pull on the right switch :-) Is he referring to the red switches between the seats?

theiceman

You should have Pmed me if you didn't understand and I would have been more than happy to help. I hace a 78sc SO IT may be a little different .

my 78 has 2 blower, a fresh air blower controlled on the dash by the **** you point out .

and heater blower in the engine compartment.

The heater blower comes on when you pull up on the lever between the seats. there are microswitches on the levers. You should definitely hear this with the ignition on . that is the blower the two hoses go to when the guys never put them back on your car. It is designed to blow air over the heat exchangers into the car when the car is idling as the main fan is not enough ( the alternator fan ).

The blower switch on the dash on my car is a 4 position electrical switch that turns on the fresh air blower under the dash. You use the next lever down to control the direction of this fresh air. You use the very bottom red lever to control the direction of the hot air coming from your exchangers.

I don't know if yours is identicle but it won't be off by much .

jdogporsche

I see...so when the utmost right lever is all the way to the right, I should hear the fresh air blower come on correct? I used to be able to hear it come on, but now I don't anymore. Also, the heater blower in the engine compartment...probably not enough to defrost my windshield right? Or should it be? I get enough hot air in the cab to keep me warm, but not enough to keep my windshield defrosted. I am having to wipe it down every few minutes while driving...especially if it is raining out.

theiceman

I think you have it now .

Yes you should hear the fresh air blower when you move the switch on the dash.

The heater blower I find is fairly weak as you suggest. You have to make sure your heat exchangers are in good shape, the hose from the exchangers to the body, and the hoses from the blower to the exchangers are in good shape. Even then I find it moderate. I have all the levers to the left axcept the bottom one on the dash all the way to the right.... it is moderate at idle but is better at higher RPM as the alternator fan is pushing the air. But it is no means spectacular. A good check would be to check against James' car when he gets it back together.

Does sound like you need to fix the fresh air blower. I hear they are not cheap but first you have to get to it and make sure it has power.

rentadate

sorry it has taken me so long to get back. I have a ton of term papers due before tomorrow.

But I have a 75 911s targa, and it had an engine swap with an 83 SC. It has a blower that sits behind the gages in the storage compartment. I figured out that much. There is also a small snail like object on the top of the motor that has a hose going down to I think the heat exchanger.

I have the levers in the center of the dash, as well as on the floor between the seats. when I push the levers to the right I get a ton of air, and it is all cold, and stays cold. When I use the levers between the seats that say "Defrost" on it and pull them both, the whole thing blows really weakly. Any ideas on how to make it so the heat blows stronger?

I'm completely guessing, but I think I need to have that slug on top of the engine replaced or somehow see if it is plugged in and working(?) Any suggestions?

jdogporsche

The one in the front is the fresh air blower. That will be cold as you mentioned. The blowing really weakly for heat when you pull on the center levers between the seats could just be the alternator fan blowing a trickle of heat, not the actual hot air blower. The hot air blower is in the back. You should test to see if the blower itself is working. I am troubleshooting this myself as well. Here are the steps I am taking.

1. Start from the rear of the electrical chain. Unplug the blower motor and apply a 12V DC to it to see if it will turn. If it doesn't, then you have a problem with the blower motor.

2. While the motor is unplugged, check the electricity in the wires leading to the blower motor. If all the switches are on and there is no power going to the blower motor, then the problem lies somewhere else.

3. Check the relay for the blower motor. Look at an electrical diagram, (PM me if you need one) to determine which one is the correct relay. When the switch is pulled for the blower motor, the relay should make a slight clicking noise on and off. If you need to, swap the relay with one that you know works to troubleshoot.

4. Check that the fuses are ok. Identify the correct fuse and make sure it is not blown (I actually did this first).

5. The switch could be faulty. The rear blower (heat) is connected to the red handles on the floor of the car. Check the switch with a continuity tester to make sure it is working properly.

6. Lastly check all the wires in the harness that powers the blower with a continuity tester.

Hope this helps. Good luck and make sure to tell us what you find...maybe we can help each other!

theiceman

Hey Jeremy way to go .. the student becomes the teacher...
on my car it is VERY evident if the rear engine compartment blower is working. Just putting on the ignition and lifting the lervers makes it sound like I have a jet engine back there. Wehn I got my car it was not working and I found the brushes had become dislodged from a loose screw that holds them in place. I would summize this is quite commen given the vibration and lack of lock tight on the screws.

i have heard that there is a back dated design for the heat that eliminates this blower.... although I doubt i would see this in Canada.

theiceman

In Case this helps ..

jdogporsche

Not sure on the teacher part...maybe more like a star student right now :-) To prove I am not yet the teacher, can you tell me what brushes you are talking about? Thanks Iceman! I have a fun weekend of repairs with the 911 planned for this weekend!

theiceman

These brushes are right in the blower assembly. If you take off our engine blower you will see two screws ( philips I think) at either side of the cylindrical motor. They are close to the base. These 2 screws actually hold the motor brushes firmly in place and should be tight. If your blower is not working check this. If you find the scres loose I would recomend dismatling the motor and checking. Mine was so badly gone that the entire end plate with the bushing in it wore out. You will know what I am talking about when you see it. It is a very simple design actually.