993 battery dead coz of engine blower fan running too long?

[rgv67]

My '95 993 cab battery dies after engine compartment blower runs (low speed) for 15mins after engine cutoff. It runs this long even if engine not warmed up yet. Oil temp constant at 9 o'clock. Just replaced engine compartment fan resistor and temp sensor, still runs for 15mins. Could this cause battery to drain? If yes, why does it run this long? Help!

[Eric86Red911]

THis will definitely cause the battery to drain,pretty quickly too. Running to the rear blower is a vertical big plastic tube with a sensor in it. Did you replace that sensor? If it goes bad (e.g. if you unplug it) then the blower will run.

[cjoenck]

The fan is also controlled by the Climate Control Unit in the dash. Actually fan is running for additional engine cooling when the engine is not running, i.e not neccessarily related to oil temperature. I would scan the fault codes and take it from there. The CCU has it's own set of fault codes.

[kang]

Having the fan run for 15 minutes shouldn't drain the battery...

[rgv67]

To answer all 3 posts:

Temp sensor inside vertical plastic tube was replaced (including resistor) but still runs this long.

If I do get a CCU fault code what is the solution? Does this mean $$$?

How long should the engine compartment fan run after engine cut-off? My battery is new (rated above std cold cranks, barely 3 months). Could it be a bad new battery? Fan motor smooth when running but I do hear a short squeel (4 seconds) at the end of fan rotation as it turns off, am speculating a heavier than usual load for battery because a motor about to go bad?

[budge96]

I doubt the cooling fan is your culprit,likely an interior light,glove box or trunk light switch.
These drains can be difficult to sort and costly battery wise,also on later '96 alarmed cars
lights and such will deplete reserves in short order unless driven daily.
Trickle charger to the rescue..

[rgv67]

Originally Posted by budge96

I doubt the cooling fan is your culprit,likely an interior light,glove box or trunk light switch.
These drains can be difficult to sort and costly battery wise,also on later '96 alarmed cars
lights and such will deplete reserves in short order unless driven daily.
Trickle charger to the rescue..

Hi Budge!

Thanks for your reply. I disconnected the engine compartment fan and the battery does not drain anymore. Does this mean the lights you mentioned above are not the culprit?

I realize I cannot leave it this way for long because this fan helps to cool down the engine after running. I am suspecting CCU. Any other possible causes will be welcome. Thanks again.

Randy

[Sumotang]

My engine compartment fan only runs after the car has got pretty hot. However, i notice that the fan under the dash seems to run for a while after i shut if off.

[dick911]

At the 993 and 964 cars the little fan at the back of the CCU always stays on for 15-20 minutes after turning off the engine.

The fan in the back (engine bay) is, as mentioned before, also for additional engine cooling after turning off the (very hot) engine.

If it keeps running 15-20 minutes when your engine is not that warm then indeed you have to suspect the sensor in the plastic tube. I have had this problem also and it was cured with changing this sensor.

Dick911

[KenKassay]

Did replacing the sensor in the plastic tube solve your problem. The fan will run continuously and the car will not start....finally disconnected the battery so the battery wouldn't die.

Did you fix yours? could you let me know if your process went smoothly and any part #'s that were used.

THANKS!

[cjoenck]

The NTC sensor in the plastic tube in the back controls the fan in the back. Additional cooling stays active for 15 min in '89 and '90 models and 20 min. for '91 and up after ignition has been turned off. If the temperature in the duct is below 40C (104F), the system does not activate. Between 104F and 167F the fan will run in low speed. If temp is above 167F the fan will run in high speed until temp. is 158F and then switch to low speed.
The whole thing is controlled by the CCU in the dash. Change the temp sensor, it's only about $35 from our host and take it from there.

Hope this helps.

[rgv67]

Originally Posted by KenKassay

Did replacing the sensor in the plastic tube solve your problem. The fan will run continuously and the car will not start....finally disconnected the battery so the battery wouldn't die.

Did you fix yours? could you let me know if your process went smoothly and any part #'s that were used.

THANKS!

I replaced the sensors in the plastic tube as instructed and the blower only runs in low speed (as opposed to high before) after shutting off the warm engine. It doesn't run at all if engine is not warm/hot enough as Cjoenck detailed above (which was of great help, thanks again!).

Before I knew that blower running for 20mins is actually normal, I was suspecting CCU as mentioned in the threads. It turned out to be just a bad battery which I never suspected because I bought it new 2 months ago. I tried a different battery and it works perfectly fine - won't drain from that running blower.

Thanks to all your replies! This is a great site!

gotta go and run to that battery dealer........

RANDY

[Traveller]

Originally Posted by cjoenck

Change the temp sensor....

A simple 30 second test will tell you if it needs replacing.

At 20C or 68F, you should measure 12.5K ohm, and at 45C or 113F, you should measure 4.4K ohm.

All one needs to do is measure at roughly 20C or 68F and see roughly 12.5K ohms.

0 ohms (an open circuit) will have the fan run continuously which is why a continuity test from the temperature probe connector terminals to the CCU connector (G/10 and G/18) needs to be done, or just measure across G/10 and G/18 (you should see the temperature probe resistance). I diagnosed one where there was a break in the wire within the harness thereby providing an open circuit and a fan that would not shut off.

[efhughes3]

Originally Posted by Traveller

A simple 30 second test will tell you if it needs replacing.

At 20C or 68F, you should measure 12.5K ohm, and at 45C or 113F, you should measure 4.4K ohm.

All one needs to do is measure at roughly 20C or 68F and see roughly 12.5K ohms.

0 ohms (an open circuit) will have the fan run continuously which is why a continuity test from the temperature probe connector terminals to the CCU connector (G/10 and G/18) needs to be done, or just measure across G/10 and G/18 (you should see the temperature probe resistance). I diagnosed one where there was a break in the wire within the harness thereby providing an open circuit and a fan that would not shut off.

Nothing like pulling up 5 year old threads just to hear yourself type.

[Traveller]

Originally Posted by efhughes3

Nothing like pulling up 5 year old threads just to hear yourself type.

Coming form someone who has 6943 posts.

LOL!

[efhughes3]

Originally Posted by Traveller

Coming form someone who has 6943 posts.

LOL!

I'm not following the LOL. I'm supposed to be embarrassed by post count? I've put a lot up here over 10 or 11 years, and totally rebuilt/rehabbed an '84 911 along the way, posting much about it. My post count wasn't from digging up ancient threads and commenting.

BTW, you spell from f-r-o-m, not f-o-r-m.

[wesleyc]

I am always thankful for any help I can get when I'm stumped... Even if it was from 5 years ago.

[efhughes3]

Originally Posted by wesleyc

I am always thankful for any help I can get when I'm stumped... Even if it was from 5 years ago.

Well, nowhere here has anyone mentioned the relay, that I can see. There is a relay that energizes the blower, and it can hang up, keeping the blower on until it drains the battery. If one were to experience these symptoms (blower doesn't shut off properly) a quick removal of the rear cover on the LH side of the engine bay, and a tap with the handle of a screwdriver on the relay, would typically knock a stuck one loose. Disassembly would perhaps reveal why it is sticking. Or, it can certainly be replaced.

[wesleyc]

I'll try the tapping with screwdriver. I went from the cooling fan running so long it was draining my battery to now it won't come on at all when the engines turned off. Even if my engines hot enough for my oil cooling fan to come on and I turn the engine off. No fan ? If I unplug the temp sensor it comes on ? This is happening even tho I put in new temp sensor. Relay and resistor ?