Buck

The dealer called this morning and my problems were caused by the Air Temp Sensor. When they replaced it the engine blower, front oil cooler blower and AC all started working properly.

I asked how this sensor could affect the other systems and they said the faulty sensor was probably doing strange things with the voltages. ??? Go figure!

cmoss

Thrice damn those electrical devils!!
Out! Out!

Cheers,
Chris

Flying Finn

Nice to see that these things don't always end up being 10 times more pricey that you first thought...

Tom T.

[quote]Originally posted by Buck:
<strong>The dealer called this morning and my problems were caused by the Air Temp Sensor. </strong><hr></blockquote>

Great news...just to be sure is this the same temp-sensor located on the engine air intake shroud we were talking about in the other thread? P/N 964.659.120.00 ?

Tom

Buck

Tom, yes it's the same part. I had ordered the resistor that's down on the left side of the tube (it's cheap) but they said the sensor was what was causing the problems.

Randall G.

That's great news, Buck. Completely non-intuitive, but ... it works. As Chris already said, "damn those electrical devils!" Sometimes there's no making sense of them, especially when a black box = CCU is involved.

Anyway ... I have (of course) tried to make some sense of your fix.

First of all, on the other thread, I did overlook one thing the oil cooler temp. sensor, aux. blower temp. sensor & evaporator sensor freezing protection have in common: the sensor ground at the CCU = G18.

Here's a complete list of components that share G18:

1)Temperature mixing valve right
2)Temperature mixing valve left
3)Footwell flap
4)Defrost flap
5)Fresh air flap
6)Mixing chamber sensor right
7)Mixing chamber sensor left
8)Evaporator sensor freezing protection
9)NTC heater fan (aux. blower temp. sensor)
10)NTC oil temperature sensor (oil cooler)

I tried disconnecting my sensor, ignition off, to see if my aux. blower ran in slow-speed continuously like everyone else's. Sure enough, it did. Must be a CCU default, similar to running the oil cooler fan in fast-speed when its temp. sensor is disconnected. Except one big difference--the oil cooler fan only runs continuously with the ignition on, the aux. blower will drain your battery into the dirt.

With the sensor disconnected, I verified my oil cooler fan didn't run continuously with the ignition on, and my AC still worked. Conclusion: the CCU will handle an open circuit input from the aux. blower temp. sensor without causing weird stuff other places.

The other extreme is the sensor shorting. A short circuit input from the aux. blower may cause weird stuff elsewhere (like the oil cooler fan running continuously). That is, a 0 ohm input might be outside the CCU's design parameters, and cause a "garbage in garbage out" sort of phenomenon. Of course, this is all conjecture ... I'm not going to test my theory on my own CCU by shorting from G18 to G10.

All's well that ends well.

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

vjd3

Buck, by chance, did you buy your 993 from a guy in Atlanta ... named ... what was his name again? Steve? Steve Schwing?

If so, that's my old car!

Vic
95 C4

Buck

Vic, I sure did! Please don't tell me it sat underwater after it was rebuilt from the fire! LOL!

vjd3

Only the interior needed to be replaced after the fire, the blisters in the paint buffed right out.

Seriously, that is a great car; Steve did all the mods to it, it was stock when it left me but I miss that full red leather interior, Flamenco Red, I think Porsche calls it. I sold it to Steve when I moved to Kansas. Now I'm in Boston with another 95 993, red C4.

Enjoy!
Vic

Mark Buka

Vic:

I'm interested in seeing jpegs of the "Flamenco" red interior. I found a car with that interior, but would like to see pics.

Thanks in advance, Mark

vjd3

Mark: I don't have photos of the interior, unfortunately, perhaps Buck can oblige.

I would describe it as a little darker than a lipstick red interior; it's not a match for guards red, and it's not quite as orangey as the Boxster red interior. It worked great on the grand prix white car, and I think it would look dynamite on a silver or black car. I can't really think of too many other colors it would work on, though. Maybe a gray.

Porsche also had a color called chestnut, which was sort of a reddish brown clay color; I saw that on a grand prix white 993 convertible and it was drop dead gorgeous. When I lived in Kansas, I came across a 96 993 C4 cabriolet in KC that had that interior, but the car was adventurine green. That was car was so ugly I think you would go blind if you looked at it for long enough. The Porsche dealer was despairing ... I could've bought it for next to nothing, and I tried really, really hard to like it, but it was just hideous!

Vic
95 C4 (guard red/cashmere)

Buck

Mark, I don't have any pictures of the Red interior handy but I'll try to get a couple this week. If I do I'll send them to you.

A.J. - 95 993

First, let me start out by thanking everyone for their very helpful, and detailed, descriptions and problem solving ideas concerning these various heat sensors. Front and rear. It has helped me immensely, though I want to make sure I'm on the right track:

I first figured I had a problem with my cooling fans because the rear fan was running erratically. The topic getting all the "airplay" was the front sensors, so I figured I'd start there first. Turns out, after jumping the terminals in the oil cooler relay terminal and the a/c, the slow speed fan didn't come on for either. The a/c fan seems to be ok otherwise - it cycles on and off when the a/c is on and the key is on... I unplugged the oil cooler plug behind the headlight, and the fan runs in high speed with the key on. I plan on replacing both resistors, and am wondering if I should replace the temp sensor. I've got quite a list of parts to buy, and I want to pay for shipping only one time if possible.

I noticed Buck's post recently regarding the rear fan, and that had much more to do with my initial concern. Tonight, I went out and ran through the diagnostics. With the #11 (I think that's it) relay in the engine compartment removed, I jumpered position #3 (forward middle terminal of the relay/socket) and #7 (bottom middle terminal), and #3-#5 (aft middle terminal) with the key on and with the key off. Nothing happened. Since 87c is not on the rear fan relay, I extrapolated the locations from the front oil cooler fan relay. It's impossbile to read the tiny numbers on the white plug, even with a flash light. I can't get my fat head close enough. I figured the plastic plug is common, same as the ones used for the oil cooler and a/c up front.

I turned on the key, turned the temp selector on the CCU to 21 deg C, and nothing happened. Turning it to max caused the blower to come on. Slow speed, I think, because I couldn't feel it standing behind the car.

With the engine cold, not running, and key off, I unplugged the air temp sensor from the harness, with the sensor still in position in the air tube. A second later, the high speed rear fan came on. It ran for a few seconds, the relay clicked and stuttered around, then the fan shut off. A second later the fan came back on, then stayed on. This clicking and on/off erratic behavior is what initially caught my attention. Once it started doing that, it would go on and off, as if trying to make up its mind, for 5 or 10 min. There was a time when this used to work properly - when engine was hot and turned off in the garage the fan would come on and stay on til it was cooled off. Anyways, re-connecting the harness to the air temp sensor, the fan shut off. The behavior did not change when doing the same thing over (a few times )

Unless I hear otherwise, I'm going to order 2 new resistors (oil cooler and a/c), and a new air temp sensor for the rear. And maybe an oil temp sensor (thermosender?) for the front. And hope that takes care of it.

Randall G.

Hi A.J.,

&gt;The a/c fan seems to be ok otherwise - it cycles on and off when the a/c is on and the key is on...

This is probably the fast-speed fan cycling, as it tries to compensate for the out-of-service slow-speed fan.

&gt;I figured the plastic plug is common, same as the ones used for the oil cooler and a/c up front.

Yes, they are. The numbers should be printed on the relay. #3 on plug = 30 on relay, #5 = 87, #7 = 87C. 30 should have 12V (it's the hot position).

&gt;This clicking and on/off erratic behavior is what initially caught my attention. Once it started doing that, it would go on and off, as if trying to make up its mind, for 5 or 10 min.

Actually, you might try swapping either the AC condenser or oil cooler relays into the rear (aux.) blower position, to see if that cures the intermittent behavior.

&gt;Unless I hear otherwise, I'm going to order 2 new resistors (oil cooler and a/c), and a new air temp sensor for the rear. And maybe an oil temp sensor (thermosender?) for the front. And hope that takes care of it.

The oil temp. sensor is cheap, about $16. You might seriously consider ordering a new relay, as well. The dealer sells them for close to $30, but I understand Pelican sells an equivalent relay for only $16. Finally, you might consider getting a new resistor for the rear blower, as well.

Best of luck!

A.J. - 95 993

The front relays are not compatible with the rear relay, are they? They don't have the same terminal layout, and the diagram on the side of the rear relay is not the same. The white plug they connect to is the same, but different terminals are used in the rear.