Alister Thomas

I have recently bought a 964 (1990) Carrera 4 with Air Conditioning. In the last 3-weeks I have had to change the fuse for the cabin heater fan 3 times (this is the fuse in position 1 in the front fuse box). It generally blows when I increase the fan speed via the dashboard control ****.

Does anyone suffer from regular blowing of this fuse? Is it common to 964's or is something wrong with mine? The capacity of the fuse that is in place is 25 Amp - is this the correct size?

Would appreciate any comments/suggestions from anyone.
Regards
Alister

Adrian

Dear Alistair,
Your fan has had it. Bearings are gone most likely which has caused damage to the rotor (goes out of balance). If the 25amp fuse is blowing you have a problem. Yes it is a 25amp fuse. There are other possibilites of course but the fan is where to start.
This fan is the LH Blower fan by the way not the cabin heater fan.
This problem is not that common because normally the bearings start screaming long before the electrical consequences occur,
Ciao,
Adrian
911C4

Alister Thomas

Adrian,

Many thanks for your advice. I shall check out the heater fan in the engine bay and see what it turns up.

I will let you know what I find.

Thanks again.
Alister

horst

Allister, I believe the engine bay fan does give trouble. I know I replaced the motor on mine. Expensive (ca $180.00??) I have heard that sometimes the cover/ housing of the motor gets distorted, and interferes with the fan. It's easy to get out, and you might try spinning it before replacing it. I always treat bearings like this with a tiny bit of Energy Release before installing.

Adrian

Dear Alistair,
Please do not get the fans mixed up. The rear blower fan is not speed controlled from the **** on the control unit.
Fuse No 1 is the LH blower fan. This fan is located at the very rear of the luggage compartment.
The rear blower fan has its own fuse mounted in the engine bay. The rear blower fan is also mounted in the engine bay.
Your problem fan circuit is the LH Blower fan. One check you can also do is wind up the defrost or RH Blower fan by pressing the defrost button on the control unit. Makes sure this fan is working properly. It will only run at one speed and that is Max. It wil also cut out or override the LH Blower fan.
Ciao,
Adrian
911C4

PS: If the rear blower fan is not working nothing else will either.

Alister Thomas

Horst & Adrian,

Thanks once again for your advice. I was just about to go and extract the rear engine bay fan when I saw your messages.

So, if I get this right (I am knew to Porsche's!) there are 2 fans in the front luggage compartment? The "Left-Hand" and "Right-Hand" fans (LH & RH respectively???).

The left-hand fan controls the standard heater volume (via control ****) and the right-hand one controls the rapid demist function. The rapid demist does work, and have not noted this one blowing the fuse.

I shall take out the LH blower (is this easy?) and do as Horst suggests.

Thanks
Alister

horst

NO-NO-No-! I was talking about the fan in the engine compartment! Adrian is right there is a fuse in the left side of the engine compartment for this puppy. Also, there was a recall/ change in the amp rating for this fuse. Forget what that was exactly- I saw that the fuse in mine was HIGHER than what was listed in the cover, only to discover that a official change had been made, and the fuse that My car had in it (higher than the the cover specified) was now the correct one. I havent been plauged by any problems in the fans in the front of the car.

Emanuele Ferry23

I've put a 30 amp fuse on my heater blower and it runs fine. However make sure your rear blower is OK. The electric fan bearings are prone to fail especially on cars with tuned suspesions which are generally stiffer and communicate more vibrations. You'd better remove it (it's very easy) and check if the fan rotates without sticking. I have replaced mine two months ago because bearings of fan shaft were literally in pieces. Before removing the unit check out for "grinder like" noise from the fan.

Adrian

Dear Alistair,
Yes there are 2 fans in the luggage compartment. You cannot miss them. You remove the flimsy cover over the whole package and you will see two humps. Looking from the front the RH is actually the LH Blower and the LH one is the RH blower. The LH blower should be running all the time even with the speed **** at 0 (power on of course). If it is not running this is a good indication of a problem.
I do not recommend ever the installation of higher amp fuses unless authorised by Porsche. This can create a fire hazard. The values are picked for a very good reason.
There is actually a procedure for removing this fan posted on this forum. You will have to go back to the beginning of the pages (top right, just up there) and find it. I hope it was not erased during the big crash,
Ciao,
Adrian
911C4

Alister Thomas

Thanks Guys,
I am not particularly keen on uprating the fuse - as you say Adrian it could cause a fire hazard. I would rather solve any issues with the first.
I have removed the plastic cover to reveal the motors. I must say it doesn't look easy or nice to remove - not much room to manoeuvre!

I've looked at the back pages of this discussion board to find a description about how to remove but could only find a posting by RobC (20-June-2001 entitled "Heater Blower Question") but there was nothing describing removal.

The LH front fan does come on as soon as I start the electrics, as does the large rear engine bay fan. I can't hear a grinding noise, it all seems fine. However I have noticed that when I increase the fan speed via the dashboard control ****, it doesn't increase speed straight away - it's sort of delayed. Is this another symptom of shot bearing?

Regards
Alister

Adrian

Dear Alistair,
How much of a delay. There may be a short, very short delay but only to allow the fan to spin up to the new higher speed. If the delay is noticeable it tends to suggest that the motor brushes have had it or the rotor is damaged. This would also account for the blown fuse.
I have the repair procedure at home (well the Porsche version anyway) but I will not be able to do anything with this for you until Monday at the earliest.
Ciao,
Adrian
911C4

Alister Thomas

Hi Adrian,
The delay can be a couple of seconds but it's not consistent. Sometimes it does react properly and begin increasing speed immediately.
Any advice you can give on extracting the fan would be much appreciated - no rush. (are there any diagrams on the web some where? - I checked out <a href="http://www.msroadrace.com" target="_blank">www.msroadrace.com</a> which has some excellent exploded diagrams for parts but nothing for the LH fan.)
Thanks again,
Alister

Adrian

Dear Alister,
Let me work on it. I am a tad stressed at the moment but I will find what I can for you. The maint manual is pretty useless on this subject. Have you physically checked the fan yet. If memory serves me correctly the motor is just pulled out of the fan assembly using a puller or if you remove two mounting screws and bend a couple of tabs back it basically pops out into your hands. Access is a bit tight. I reckon if you have a look (remember LH fan is on your right looking from the front) it might become clearer,
Ciao,
Adrian
911C4

Alister Thomas

Hi Adrian,
I haven't managed to get the LH fan out yet. I have raised the plastic cover, had a look and was a bit loath to attempt to take it out without any advice - as you say, it's a bit tight. Don't panic about getting info to me, I can't do anything until the weekend, and I'm grateful for anything you can suggest. I'm sure that once I remove the plastic cover fully (it appears to be tightly fitted to the rubber seal running across the engine bay) it will become clear on how to go about removing it.
Thanks again.
Regards
Alister