nile13

My blower doesn't seem to work the way it shouls. Goig through 1-2-3-4 blower speed sequence doesn't appear to increase airflow much. It seems that there's very little difference between all 4 speeds, if any.
Is it normal? Is blower speed related to the oil temperature or is it completely manual? Where do I look to fix it? If tehre's a resistor pack that controls blower speeds, where is it located?
TIA!

Randall G.

Hey Mike,

I take it your speaking of your interior fan, as opposed to the rear (auxiliary) blower in the engine compartment. The interior fan speed is controlled by the CCU, via a "final stage regulator." The CCU controls interior fan speed by varying the final stage regulator's resistance.

Incidentally, the interior fan is actually two fans. Left and right, in the luggage compartment.

The rear blower does use a ballast resistor to create slow-speed operation. It only has two speeds--slow or fast.

The interior fan not operating usually means the rear blower fuse has blown. If the rear blower isn't running--as it should when supplying heat--it causes the interior fan to cut-out.

If your problem is with the rear blower, the interior fan should still operate normally when you're not requesting heat. For example, at blue dot (coldest setting).

Hope this helps, and let us know what you find.

nile13

Randall, thanks! Now I'm even more confused :-)
I was talking about my interior blower fans, yes. I only tried them at high heat so far. The air does come out of central registers, but only at fairly slow flow and that doesn't change much with **** position.
If I understand correcly, you think that the rear ballast resistor is bad. It should be possible to check, than, by running the blowers on low heat setting, all the way counterclockwise?
OK, I just got out and tried it. Indeed, the blower changes speeds perceptably when temp control is on full cold. The speeds change tiny amount (you can hear the fans change pitch, but you can't really feel the difference in air flow) when the control is on full hot or anywhere in between. Of course teh car is cold at this point.
So... sounds like the ballast resistor? Or more like computer control? Where exactly is ballast resistor located?
Thanks!!

Randall G.

Hey Mike,

I originally wrote ballast resistor, and later edited it to say fuse. Though, strictly speaking, a bad ballast resistor could cause the same problem (since the rear blower wouldn't run in slow-speed).

Were you able check if your rear blower is running, ignition on, heat at highest setting? If not, you should check the fuse for the rear blower, in the engine compartment fuse box.

If the fuse is blown, you can replace it, and hope it doesn't blow again. But, more likely, your rear blower is wearing out and seizing, causing the fuse to blow. Which means you'll need a new rear blower. Common problem, unfortunately.

If the fuse is good, the next thing to check is the ballast resistor. But, let's check the fuse, first.

nile13

OK, I'm even more confused :-)
Which rear blower are we talking about? It's a cab, if that matters.

Randall G.

Mike,



The rear blower is just above and to the left of the rear shift flap shown in this photo. The engine compartment fuse box is all the way to left from the rear shift flap. Here's a pic from E.J.'s website:

http://www.pcarracing.homestead.com/...ection_box.jpg

nile13

OK, great, thanks!
The fuse (30A) is fine. It seems I will need to take off some plastic tubing to see the blower? Is it enclosed in a round black plastic housing about 8" in diameter?
It's cold and dark, I have an ice race tomorrow, so early next week I will have to take things apart there and look.
So far the summery as of today (outside temp is about 35F right now):
1. The speed control works fine when temp control is set to cold.
2. The speed of outgoing air changes somewhat when the ignition is on, almost none when ignition is running if temp control is set to hot. There's a differemce now between, say, positions 1 and 4, but very little difference between 1 and 2.
2. When defrost button is pressed the air to the front widow is estimated to be equal to position 3 on the blower if temp was set to cold.

Randall G.

Mike....

Now that you know the fuse is good, you need to see if the rear blower starts up when you "request" heat. Say, interior fan set to 1, temperature control set to (say) maximum clockwise (red dot), ignition on.

Yes, the actual blower is inside the casing, and is connected to the ventilation ducting. However, if you have to buy a new one, it will come with the case. There was a time when you could buy just the blower for a 964, but I don't think that's the case anymore--and don't think it ever was for the 993.

nile13

Randal, just to re-iterate: the rear blower should only start when the car is running and heat is requested?
Is there an easy way to look into that housing, or does it have to come apart?

Randall G.

Mike,

The rear blower will actually run with the ignition on--but engine off--to attempt to provide heated air (of course, with a cold engine, the air won't be hot). So, it's quite easy to hear if it's running or not. No need to tear the fan casing open.

If it comes to this, you can also install a simple jumper across the relay plug, to (hopefully) make the rear blower run. Which will give you an idea of what you should expect to hear.