8valve

I need some help on a SES Light/Fans Running problem. The car is 1995, 6 speed.

Late last summer, my AC was not real cold. I added some R134A, only needed about 1/4 can. I set the gauge to the outside temperature which was by memory in the 70's. I added R134A until the needle was between the upper and lower lines of charge. The AC worked fine, and still does after a long winter layup. I cant remember if the SES light/Fan issue started right after the R134A was added as it was time for winter layup. Thats a little background.

The car runs flawless in every respect except to the following problem.

When I start the car (cold) both fans come on high and the SES light comes on. I pulled the codes C72, H41,H72,H32, H43,H72, from my FSM Book 2, it appears that c72 is Vehicle Speed Sensor Loss ?

I disconnected the Battery to clear codes. After lunch, I checked the codes and had a C12, which I believe shows all is well ?

The car cold to 177 degrees runs both fans on high with the SES Light on. At 177
Both fans shut off and SES light goes out. When temp reaches 180, both fans on high and SES light on. At 186 fans and SES light shut off. AT 201 fans on high and SES light on. Temp drops to 193 and fans shut off along with the SES light.

At 190 degrees fans on high and SES on for about 30 seconds. AT 188 degrees fans on high and SES on for 15 seconds or so, very short cycle. Now the fans and SES light cycle about every minute or less.

In the past my fans would come on low at 224 degrees (no SES light). I have never seen temps up to 235 degrees to turn on the high speed fans. I shut her down and read the codes C72, H72, H43, H72.

The FSM Book 2 states that High AC head temp over 248 degrees will turn fans on high. I only have the gauge that comes with the R134a refill kit. I checked the pressure at the low suction where you add R134A today and at 70 degrees it was 34 spi, which is within the lines for a proper charge ?

Thats where I am......lost. Could the AC be overcharged, causing the problem ?
Oh, and no matter if the AC is on or off, the Fans cycle and SES lights cycles and described above.

Thank You for your help

8Valve

antfarmer2

Could you have bumped the temp sender on the water pump? They can do some strange things. And check your battery connections and how old is the battery?

8valve

No, did not bump the temp sender under the water pump. The only work under the hood was add the R134a and normal oil checks. However, tomorrow, I will check that sender to be sure the wire connection is clean and tight.
The battery was new last fall, after the problem with the SES light started. I cleaned the terminals but will also do that again tomorrow.

As a side note, all info I gave on my first post was with the car stationary, sitting in my shop.
On the open road this car temp has never gone above 185 on the analog gauge, cant read the small digital numbers without my reading glasses. I live in the Mts where is is always cool, thus I believe the 185 temp. My C3 never goes about 190.

Thanks for your reply
8Valve

8valve

The SES and Cooling Fans cycling is fixed ! I had been getting a Code 43 (Knock Sensor Circuit). I cleared all the codes this morning, started her up and still had the SES and Fans cycling.

I shut her down and following the FSM Book 2, I went under the car to look at the Knock Sensors. Problem Found. The right knock sensor wire had rubbed on the edge of the sensor heat shield. When the general built this car they pulled the right knock sensor wire quite tight. The Heat Shield had a sharp edge that over the years wore through the insulation. You could see and easily feel the cut. It was not a dead short I dont believe but rather shorted when vibrated. I lengthened the wire slightly, soldered the splice and heat shrunk it. Also just bent a tiny radius in the heat shield end.

Started the car, no fans running, no SES light ! The car started to warm up, still all was well. The car past those 180/190 degree reading I posted yesterday and was acting normal. Temperature climbed to 228 degrees and the fans came on low. Temp dropped, fans shut off....NO SES LIGHT. I let her run for 1 hour cycling with the engine heat going to 228 and fans cooling her down. All was perfect.

I have no idea how that intermittent short caused the fans and SES light to cycle, but it did. Now for the BONUS !!!!!!!!!

I have owned this car for almost 4 years. Over those years I have tried to get Tuner Pro RT running. ALl I ever got was DA connect/DA Error,fast and constantly.
One super great guy sent me quite a few ADX files to try. He felt there was noise somewhere. Nothing worked, nothing at all, it was a nightmare. Well after the Fan/SES problem was smashed, and the car still running, I thought why not try Tuner Pro RT once more.

Fired Tuner Pro RT up and it was steady as a rock. It worked beautiful and reads everything properly. I let the car run for a extra hour to test the SES/Fans and now with Tuner Pro RT running. Never, Never in that extra hour of running did Tuner Pro RT ever get a error. It was 100% solid . Somehow, known by people way above my Pay Code, that Knock Sensor wire vibrating intermittent short also wacked out Tuner Pro RT.

WOW, I am quitting today while I am ahead ha ha

8Valve

antfarmer2

Good job and a great day!!!!!!!!!