Greg D.

You guys are something else... within 5 minutes of asking about fan info for my "new to me" 993, I was pointed to the P-car site and the Fan troubleshooting section.

I followed instructions and jumpered terminals of the fan relay, and much to my surprise, the slow speed fan did not work at all !!! The fast speed worked fine so I know my jumper technique is not the issue. That makes perfect sense, because when I drove the car home I thought the temps were a bit too high and then heard the fan kick in to bring 'em back down, but that was at the point where the high speed fan would have kicked in.

Now my dilemma... Sebring DE saturday... I gues sI could take out the pass headlight and make the fan run hi-speed all the time. Not much time to go buy the relay and install it considering the car will be at the dealer until thursday night for tires, alignment, discs and pads. I'd love to do this myself but from what I read it's a royal pain in the *** requiring triple jointed elf fingers and I am thinking that with the wheel and rotor off, the dealer mechanic might have an easier time reaching there than me ! What would you do ? ;-) I'm already gonna pay enough but maybe that makes sense while they're in there? (all I need is a little encouragement I guess)

Anyhow, I am happy to have diagnosed this thanks to you guys, and kudos to the P-car site founder and contributors for top nothch info! This is going to be fun with this kind of help being available !

Thanks again! Greg.

Jeff 993TT

Personally, I wouldn't pay the dealer to replace the resistor. There's a lot of labor involved in removeing/replacing the front bumper.

For your DE, I'd just do the oil cooler fan switch and have your fan run in high speed all the time. At least you can control that from the cockpit.

It's an easy DIY and you can do it in about 1 hour ( or 3 hours if it's your first time )

993,951,944

Greg:

The attached is on opened oil cooler relay.
The same relay is also used for the air conditioner.
I have a blown 0.45 Ohm ballast resistor, but I modified my
relay to bypass this resistor. I carefully soldered a jumper wire
across two terminals, as indicated in the photo.
I never have temperatures higher than the 9 O'clock position,
as the jumper wire allows full power to the fan during the slow
speed temperature status. I prefer this mod over installing
another underrated -doomed to fail- ballast resistor.
This also makes life easier for the engine.

<img src="http://" alt=" - " /> <img src="http://boards.rennlist.com/upload/Oilcoolerrelayopened.jpg" alt=" - " />

Greg D.

Sounds great David. Across which 2 terminals exactly ? The mod jumper looks fuzzy to me, it might make more sense when I open the relay, but if you wouldn't mind explianing a littl emore I'm all ears! Thanks !

Greg.

993,951,944

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Sounds great David. Across which 2 terminals exactly ? The mod jumper looks fuzzy to me, it might make more sense when I open the relay, but if you wouldn't mind explianing a littl emore I'm all ears! Thanks ! </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Sorry the Image isn't clear; it's a 460K pix camera.

One side of the jumper is connected to the back side of
the low speed relay contact and the other side is connected
to the conductor line. If you remove the relay plastic cover,
you'll see where the jumper is soldered. The air conditioner
relay is identical and can be swapped with the oil cooler relay.
This can help in event of a failed oil cooler relay.

<img src="http://boards.rennlist.com/upload/Oilcoolerrelay2.jpg" alt=" - " />

Greg D.

Thanks! I wasn't sure whether I was supposed to be looking at the big tab joining both sides or the little jumper thingie(?) on that tab. I guess it'll all make sense when I get a spare and crack it the relay open. Sounds like a good idea anyway as I live in Florida and the low speed setting makes little sense, it's always HOT! ;-) Thanks again !

Randall G.

Greg,

You could also simply connect a wire between terminals #5/#7 of the relay plug. However, you would want to use a decent sized wire (2.5 mm2, a little larger than 14 AWG), as it will be carrying somewhere close to 20A, and I'm not sure how well the relay will sit on top of such a wire (I know it will sit flat on a small gauge wire). David's relay mod is cleaner.

On the relay, you're looking to connect terminal #87 to 87c. 87c = 12V power out for the slow-speed fan. 87 = 12V power out for the fast-speed fan, ballast resistor shunted. Porsche uses a 2.5 mm2 (a little bigger than 14 AWG) wire for the fast-speed power supply, so you'll want to use the same size wire (or larger) for your 87/87c jumper. 87 & 87c are printed at the plugs on the bottom of the relay.

You could also go below the fuse box, and connect #5 to #7 at the oil cooler relay plug. But, this would likely require cutting your car's wiring. I would rather bastardize an ~$25 relay than cut my car's factory wiring.

Lots of choices here, Greg <img border="0" title="" alt="[Wink]" src="wink.gif" /> . Replace the resistor, disconnect the temp. sensor to force fast-speed operation, install the hi-speed switch, jumper 87 to 87c on the relay.

Greg D.

Thanks Randall! I am still debating which way to go -at least initially, i am leaning towards replacing the ballast resistor to restore the car to its "normal" mode of operation, but if the resistor will blow again within 6 months, I might as well do the relay jumper trick and have the high speed fan activate at lower temps (that's what this mod does right?). For this w/e, I'm going to do the headlight trick for Sebring, should be good enough. Oddly enough, instead of being bummed I have to do this on my "new" car, I am looking forward to it! Sounds like a good way of bonding with the car ;-) Thanks for everything, you guys are great - couldn't ask for me help !
GReg.

Dave R.

David,

That's a great idea to modify the relay!

If I understand correctly, you are bridging/jumping the control signal that energizes the low speed coil of the relay, to energize the high speed coil also.

However, this doubles the load on the low speed control signal, since it must now drive both coils.

So, why not also sever the lead in the relay that connects the low-speed control signal to the low-speed coil? (Downstream of the jumper, of course. )

[Edit2: Hmmm, I was assuming you were bridging the control signals supplied to the relay, rather than the output currents from the relay. If you are bridging pins 87 and 87C as Randall mentions, that would avoid the issues I pointed out. However as Randall notes, a bridge between contacts 87 and 87C of the relay would have to carry the full current that drives the oil blower motor rather than a much smaller control signal current.]

-Dave
'90 C2

LarryN

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> ... but if the resistor will blow again within 6 months...
GReg. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Not positive, but I seem to recall that the replacement resistor is a revised part, so hopefully it won't go bad again. Both of mine were replaced 1 1/2 yrs ago and work just fine.
-Larry

Pete Lech

The replacement relay has a heat sink integral with it. Mine has been fine since I put it in 1-1/2 years ago. I replaced the AC relay also while the bumper was off as a precaution.

993,951,944

I chose to jumper inside the relay as it was an easy modification,
and it doesn't require cutting any wires.
I used a section of solder wick for the jumper as it's heavy
enough to handle the current and the flat dimension allowed
the plastic relay cover to be re-installed.

If my resistor wasn't blown, I would still use this jumper.
(Or install jumper between #87 and #87C terminals as suggested)
The resultant cooler oil temperatures are better for the engine and
the circuit still works automatically. I'm very happy with the results.
I believe the engineers wanted the fan to run quiet in slow mode
to quell any noise complaints as well as, theoretically, extend
the life for the blower fan. However, we all have experienced the
frightening oil temperature rise. I put priority on protecting the engine,
so the slow mode resistor will not be used.

Randall G.

David,

Now my curiosity is piqued. Did you jumper 85 to 85c (control "signals" from CCU)?

Nice work, btw.

993,951,944

<img src="http://boards.rennlist.com/upload/RelayundersideJumper.JPG" alt=" - " />

Randall,

The internal jumper does the same thing as placing a jumper
between relay terminals #87 and #87C.
I discovered that using copper tape makes
it possible to jumper external to the relay.
It connects the low speed relay
(Low speed because it's sending voltage through a 0.45 Ohm
series ballast voltage dropping resistor) directly to the cooler fan
enabling full speed cooling during medium-high oil temperatures.
High oil temperatures engaging the high speed relay mode will
not change the cooling fan full speed status. Although, the
temperature never goes past the 8:30-9:00 O'clock range, as
the fan engages at full speed (instead of low speed) during this
temperature range.

The bypass does not involve any changes to the control signals
from the DME. Although, that could be another way to accomplish
the same result.

Dave R.

David,

Elegant solution!

I modified my relay internally with a double length of solder wick (Radio Shack) to effectively bridge terminals 87 & 87c as you described above. A deft touch with the soldering iron is certainly helpful. Modified relay functions flawlessly. <img border="0" alt="[jumper]" title="" src="graemlins/jumper.gif" />

The bridge handles the current fine, it was cool to the touch after I ran the fan at high speed for a while.

Thanks for posting. <img border="0" alt="[bigbye]" title="" src="graemlins/xyxwave.gif" />

-Dave