chili964

Well the HVAC gremlin seems to be striking again. Got in the 964 this afternoon, started the car, turned the a/c on and fan swith to 4....nothing. Number one fuse was blown. Replaced with 25A, went to turn on a/c and fan...another blown #1 fuse. Replaced with 30A fuse (I know, I should not have). This time a/c engaged, fan switch worked, but weak air flow from center vent. The rear blower fan is working (ran diagnostic per previous threads).

Anybody know what may be causing this problem??

Randall G.

Hi Chilli,

Fuse #1 is for the two interior fans. Looks to me like you have a bound fan, causing the fuse to blow.

chili964

Thanks Randall. From previous threads, I know you have experience with these components. When I replaced the blown 25A fuse with a 30A fuse, the a/c worked and the fan switch worked. Except now I have poor air flow from the center vent. I do not feel comfortable with the 30A fuse and the poor air flow.....the GREMLIN is back.

Can you suggest some diagnostics I can run to see which fan is blown.

Art
90' C4

Randall G.

Hi Art,

Adrian S.--who is usually right about these things--has written in the past that the left-front blower is for the interior fan, the right-front for the defrost. Assuming this is true, then you should be looking at your left-front blower. However ... when I operate the interior fan **** or defrost button, it feels to me like both fans are running (based on feeling the fan housings). In addition, when you press the defrost button, a servo motor repositions to send air to the windshield. So, I'm not sure why a separate fan would be required. I'm looking for clarification here. Anybody?

All this said .... the left and right-front fans share fuse #1. Both have a 2-pin connector. One pin (#1) comes from the "blower final stage." I assume this is how the motor's speed is controlled. The other pin (#2) is the 12V power supply. If you can find these connectors, you can disconnect them in turn, to figure out which fan is blowing the fuse (after reinstalling a lower rated fuse). Also, you can see if there's any change in your interior air-flow.

Another interesting test you might try. Reinstall the lower rated fuse, and hit the defrost button--which causes the fan to run in max. speed. If the fuse blows again, I think this is evidence that both blowers operate at all times. That is, the fuse blows at both position 4 on the interior ****, and when running the defrost (I don't think it's very likely that you have two bound fans).

Best of luck!

WMRiceman

Same thing happened to mine and it was the right blower that had a bearing failure. Blowing the same fuse. You can replace the little motor with not too much of a hassle, does require some taking things apart. (fuse box up and laying on a protected fender, long piece of black plastic in the back removed, and the metal fire wall at the back of the fuel tank removed, all sounds worse than it really is) When you get here you see both of the blowers. Now take off the outer shell of the blower that is not operating. The manual calls for a special Porsche tool to slide in and get the blower to pop out of the housing. The manual doesn't however say anything about the 2 little screws. When you get the blower shell apart slowly rotate blower wheel and look for the two allen screws and take them out. The blower has notches that line up with these. Now for the trick with the tool, take a hacksaw blade and bend it into a squared "U" and when you slide it in, the blower will fall out in your hand. Mine did but you might have to pull on the wheel some. The tool goes in and pushes down 2 clips that hold the blower in. You will see what I'm talking about when you look at it with the shell apart. There are 2 openings on both sides that require this tool. If you don’t take out the 2 screws, even with the Porsche tool it will never come out. I’m betting that when you get the long black piece of plastic out and the metal fire wall removed you should be able to start it up and be able to hear and feel which one is having a problem. Mine was very apparent.

I got mine all apart and took it to Brumos Porsche to get them to use the special tool to get it out. After a while he said he couldn’t get it out. I took it back home and found the 2 screws. When I saw his tool, the blades that slide in looked the same dimensions as the hack saw blade, and wola it worked. Mine has been working fine now for 2 years. I bought my blower from Porsche for $189 but I know better now, vertex has it for $94.00

Hope this helps, Mark

Randall G.

Hi Mark,

I take it your fuse was blowing when you turned the fan **** to 4? If so, I tend to believe that both fans run for both the interior fan **** and defrost button. Watcha' you think?

WMRiceman

Your right, the fuse would blow and both front blowers would stop. Mine was blowing the fuse on other settings as well (2 through 4). For a while I just kept some 25A fuses with me but then it was happening all the time and the sound was getting worse. If your bearings are failing and causing the blower to pull too much current it will blow the fuse, other settings just puts a resister in series with the motor so logic says it should blow in setting 4 more often when most of the circuit load is generated by the motor resistance.

When I got the half shell apart and wiggled the squirrel cage blower around it was easy to tell the bearings were shot, especially with a new blower motor in hand. I even turned it on and watched and listened to it try and work. If your left blower is the problem, it’s going to be a littler tougher to get at with the A/C lines in there but it’s workable. Just don’t wiggle the A/C lines much, last thing you need is a freon leak.

All I can say about removing the metal firewall is be very careful not to drop any nuts or bolts down in that never never land behind the fuel tank. I didn’t but was worried the whole time.

If it is a blower and you go head and buy the new internal motor, look at the back and you will see the round black plastic back. You will see the 2 holes where the screws go. This is what led me to finding the screws. Like I said the manual says nothing about these and I just couldn’t get the thing out. Looking at the new motor in hand I notices the 2 holes and then looked at the installed blower and saw them. Took them out and used my hacksaw blade tool and it fell out in my hands.

If I was a betting man I’m betting on you have a bad blower but take it apart and check it out. You can even turn it on with the outer shell off and watch it spin or lack there of.

Take care and good luck with it, mark.