Jeff 993TT

Thanks to Randall G's excellent posts, I completed the installation of my oil cooler fan switch. And just in time also, since I'll be at Thunderhill ( in Sacramento ) this weekend.

I verified the correct operation today. My slow speed comes on about 221 degrees. I fliped the switch and my high speed came on instantaneously.

The temperatures really do drop quickly once the high speed fan is on.

Here are some pictures of the installation:

<a href="http://www.cuberootconsulting.com/photos/photos.php?RollID=pictures%2FHobbies%2Fcar%2Fporsche%2Foil_fan_switch&Fr ameID=111-1119_IMG" target="_blank">

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<a href="http://www.cuberootconsulting.com/photos/photos.php?RollID=pictures%2FHobbies%2Fcar%2Fporsche%2Foil_fan_switch&Fr ameID=111-1121_IMG" target="_blank">

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<a href="http://www.cuberootconsulting.com/photos/photos.php?RollID=pictures%2FHobbies%2Fcar%2Fporsche%2Foil_fan_switch&Fr ameID=111-1122_IMG" target="_blank">

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Jeff

ps, I thought about this a bit more, and wouldn't it have been easier to just replace the thermostat with one that "triggers" the low/high speed at a lower temperature?????

993C4

Jeff,

Nice pics. Do you have any pics of how you did your wiring. I presume the wiring was through the CCU? Any problems removing the CCU and identiyfing the correct wires to cut?

993C4

Jeff 993TT

I routed the wire down to the CCU. The wire is G12, the green/black wire. I removed the CCU unit to verify that I got the correct wire, but that is not necessary. You can also route the wire to the fuse box ( the andial solution. )

I'd do yourself a favor and use wire taps instead of trying to solder the wires. It's kind of difficult under the driver's dashboard on your back.

I can put together a step by step diy if there is any intrest.

Jeff

STLPCA

[quote]Originally posted by Jeff 993TT:
<strong>I can put together a step by step diy if there is any intrest.</strong><hr></blockquote>

Jeff - I'm interested.

993C4

[quote] I can put together a step by step diy if there is any intrest. <hr></blockquote>

I'm interested too (add pics if possible)

Edward

[quote] I'd do yourself a favor and use wire taps instead of trying to solder the wires. It's kind of difficult under the driver's dashboard on your back.<hr></blockquote>

Respectfully, I disagree. When one does a job, one generally wants to do it once, and do it right (for all the obvious reasons). If what you refer to as "wire taps" as those little plastic clamshell-like clamps that splice inline to a wire, these are unreliable in the long run. Yes, they work for now, some will even work for quite some time from now, but many will fail because it is an unreliable electrical connection. When I installed stereos/alarms (professionally) as a work-my-way-through-school job, I saw MANY cars come in with stereo/alarm gremlins due to these little boogers. These taps are easy and fast, which is why many installers used them...the shop I was in didn't. Likewise, our only "returnees" were for upgrades and never for intallation issues. Sorry for the longish post, but if one of my friends were using one of those splice thingies, I'd say "solder," or at least use a crimp with a good crimping tool, and you'll be doing it only once. Just my thoughts, FWIW.

Edward

BTW, Jeff, nice job. I did mine about the same time Randall did his. Great to see that temp drop, especially in hot traffic, eh! I'd recommend it to anyone who either tracks their car or commutes in a warm climate.

Allen

I will have to agree with Edward...the in-line wire splices are definitely not the way to go if long term reliability is important to you. I can, however appreciate the "complexity" of laying on your back soldering something above your face ...goggles and a towel are manditory

Randall G.

[quote]Originally posted by Silver Bullet:
<strong>Looks great Jeff! I don't know if you could find a different temp sensor to fit the oil cooler.</strong><hr></blockquote>

I'm with Kim on this one. Actually, I think Roy Eames of the 964 board tried to locate one with no success. It would need to be a NTC type sensor, and read about 1k ohms at the desired start temp.

dsinn

[quote]Originally posted by Randall G.:
<strong> It would need to be a NTC type sensor, and read about 1k ohms at the desired start temp.</strong><hr></blockquote>

Has anyone tried to put a resistor in-line with the existing thermostat?

As I understand it the factory sensor works by resistance increasing as temp. increases, thus adding more resistance would shift the thermostat and make it report a higher temp then actual.

Anyone know the actual temp to resistance values?

David

Jascha-M

On a related problem...


I decided to do some probing of my high speed oil cooler fan as per Randall Granaars detailed contribution to DIY (http://p-car.com/diy/fan/) but got some unexpected response...(?)

when I "jumped" terminal 30 and 87 (on the R04
-Relay) the fan started to run at high speed but did so for a very short time... I kept blowing the 30A fuse!

Any suggestion as to the reasons...?

<img src="confused.gif" border="0">

Randall G.

The oil cooler temperature sensor is a negative temperature coefficient (NTC) sensor, meaning resistance drops as temperature increases.

Here are the sensor's resistance specs, from the shop manual:

3.6-4.0 K Ohm at 60C (140F)
1.4-1.6 K Ohm at 85C (185F)
0.9-1.0 K Ohm at 100C (212F)

Without finding a suitable NTC sensor, I did think of a way to start the oil cooler fan sooner, automatically. Here's a diagram of my idea, with G12 & G18 coming from the CCU:



The objective is to adjust R1, in parallel with the temp. sensor, until the desired start point is achieved. Since the temp. sensor is not linear, getting an exact start point may take trial and error (variable resistor?).

For example, assume that you want your oil cooler fan to start at the temperature corresponding to temp. sensor resistance = 1200 ohms (somewhere between 185F & 212F). Also, assume the CCU starts the oil cooler fan in slow-speed when it "sees" 1k ohm (212F):

1/1000 ohms = 1/1200 ohms + 1/R1

R1 = 6000 ohms

Interestingly, R1 wouldn't need to be mounted near the sensor--it could be mounted directly below the CCU. That is, G12 & G18 could be tapped directly from the CCU.

All this said ... probably easier to just install a switch.

One more thought. If R1 was a variable resistor, it could be used as a switch by dropping resistance to some low value .... say, 500 ohms. Analogous to shorting the sensor.

Jascha-M

R:

I got it to work...

I found a pin hole in the motor body that I could spray some contact point cleaner (blindly) just to see if I can get the current draw to go down (slow speed)... it
did help some (8A ---&gt; 7.5A)

I ("inadvertently") placed the meter in series with pin 5 (not 7) and noticed that not only the meter fuse (10A rated) did not blow but the current draw (high
speed) was 22A and drooping to 11A as the motor started to run more freely (but with fluctuating speed).

The down side is that now I have the high-speed function but with a loud tapping sound from the motor --no way to lubricate it (so he said)

Sounds like I may have to change the motor...
Cheers,

Jascha

Randall Granaas wrote:

Hi Jascha,

&gt;The interesting thing is that I did not experience fan-related oil cooling "problem" (ignorance is bliss) until I decided to implement manual override for
high speed (the fuse was OK ) as precautionary measure for the hot day to come.
Not too surprising, as it's very rare for the fast-speed fan to start automatically. In all but the worst cases, the slow-speed fan will cool the oil. It's a
sequential thing ... the CCU will only start the fast-speed fan if the oil continues to heat up (the temp. sensor's resistance continues to drop).

Best of luck in the morning,

Randall


J.Y . Kresh wrote:

Hi Randall,

I was in the garage when your e-mail arrived trying to rotate the blade with a throat retractor (lollipop stick) and decided to take the "mudguard" off...

There a slight resistance (~ normal) to manual rotation (counterclockwise) and a click on clockwise rotation (I could not hear same on the A/C fan) but its
getting late so I will put the p-car on ramps tomorrow and look some more...

The interesting thing is that I did not experience fan-related oil cooling "problem" (ignorance is bliss) until I decided to implement manual override for
high speed (the fuse was OK ) as precautionary measure for the hot days to come.

Will try your resistance reading suggestions AM

Many thanks for the help!

Jascha

Randall Granaas wrote:

Hi Jascha,

Hmmm ..... well, the fuse not blowing when running in slow-speed seems to argue against an obstruction. Still, a few thoughts:

1) When the fuse blows, can you hear the motor suddenly stop, then the fuse blows? That is, can you tell which happens first--the motor stopping, or the
fuse blowing? Of course, if the fan stops first, that would argue in favor of an obstruction.

2) You might try taking off your mudguard, and performing a visual inspection of the cage surrounding the fan. Look for debris or possible interference.
Further, you could mark a visible blade, and see if the fan stops at the same place (or very close) every time the fuse blows.

3) Try taking a resistance reading from terminal #5 of R04 to ground before installing your jumper. Then, as soon as the fuse blows, quickly remove
your jumper and take another reading. Perhaps you'll find the resistance to be super low? If it is, keep watching the resistance, and see if it starts to
climb back up. Of course, this would argue in favor of an electrical fault that only manifests itself in fast-speed.

Again, I tend believe that you don't have a wiring short external to the fan. If you did, the fan would never run.

Best of luck, and will talk to you soon.

Randall

J.Y . Kresh wrote:

Guru Randall,

You are indeed a marvel of p-electric insight and good hints!

I did some more testing and here is what I found:

1. Plug disconnected (with relay R04 in place) forcing high speed to run, also blows the 30A fuse(s)
(this method seems to work for everyone on Rennlist who tried it...)

I followed you instruction from the DYI in toto

1. The slow speed jump works fine! (no fuse blow)

- The voltage drop is ~ 4.2 volt

- Measured resistance ~ 0.9 (measured across terminal 5-7 - noted some flactuations; btw, the A/C resistor was ~1.2ohm )

- Current draw at slow speed ~7 amp (taken in series with terminal 3-7; the onset transient was ~12 A)

- computed resistance ~0.6 ohm (4.2/7)

At first I thought that perhaps the relay has a diode or capacitor to remove the high transient on contact but the disconnect of the sensor cable doing
same suggest otherwise (?)

Unfortunately my Fluke ampmeter will not read over 10A so I can't tell how high the current spike is. Used a number of different source 30A fuses
--same response (I guess the green fuse is not slow blow...?)

Randall, is there anything else (other than a south going motor) that might be doing it (?)
(bad wiring causing high current drain... or ?)

Hope you can help.

Cheers,

Jascha

Randall Granaas wrote:

Good morning J.Y.,

I can think of four things that would cause the fuse to blow:

1) The fuse isn't really a 30A fuse. The motor is going to draw some 15 to 20A in fast-speed, 9A or so in slow-speed
2) The wire to the motor is shorted. But, if the motor's wiring was shorted, it would never run (but you observed it running for a short period). That
is, current would take the short (bypassing the motor's resistance), and simply blow the fuse without running the motor.
3) The motor has an electrical fault that manifests itself after the motor has run a short while.
4) The fan is hitting some sort of obstruction. For example, there's a rock in the fan's cage or the cage is bent. This seems like the most likely cause.
How does the slow-speed jumper work? If the fan will run continuously in slow-speed without blowing the fuse, it makes the "obstruction" theory
less likely.

Talk to you soon,

Randall

P.S. Yes, I need to ask Robin to update my e-mail address on his DIY page. I no longer use "flash.net"

J.Y . Kresh wrote:

In case you no longer use the old e-mail address...

Randall G.

Good morning Jascha,

Well, that's good news .... of sorts. At least you've found your problem. I think it's safe to say that the motor failing is uncommon.

As for your replacement fan, I would try either Hendrick (NC) or Sunset Porsche (Oregon). Both offer great mail order discounts if you're not local. Sunset sells all factory parts for 15% above cost. Remember to ask to the Excellence magazine discount when you call.

&gt;I found a hole in the motor body that I could spray some contact point cleaner (blindly) just to see if I can get the current draw to go down (slow speed)... it did help some (8A ---&gt; 7.5A)

Pretty resourceful!

&gt;I (inadvertently?) placed the meter in series with pin 5 (not 7)

Pin #5 is the fast-speed power supply. By placing 12V at pin #5, the 0.45 ohm slow-speed resistor is (bypassed) shorted. #7 (slow-speed) routes 12V through the resistor.

&gt;and noticed that not only the meter fuse (10A rated) did not blow but the current draw (high speed) was 22A and drooping to 11A as the motor started to run more freely (but with fluctuating speeds).

Thought you only had a 10A meter? Anyway, very, very interesting ....

&gt;The down side is that now I have the high-speed function but with a loud tapping sound from the motor --no way to lubricate it (he said)

&gt;Sounds like I may have to change the motor...

Yes, I think the loud tapping seals it--especially if you can't find a mechanical obstruction. On the plus side, it's only a ~$100 part. Cheap, in Porsche $$. ;-)

&gt;We probably should share this exchange with our Rennlist buddies

Yes, it may help someone ... especially since it's the only documented motor failure I can remember seeing since joining Rennslist in March of '01.

Talk to you soon!

Randall