I picked up my first FI car a few weeks ago. It is a 2003 Z06 with an A&A P1SC Procharger kit. It has a single front mount IC as well as Dewitts rad and 180 degree thermostat.

It was recently tuned at Synergy motorsports and made 589/501 on their dynopack chassis dyno tuned for 91 octane.

I have run into a problem with heat! When sitting in traffic on a 100 degree day, fresh black-top (car is black as well), I watched the coolant temp steadily rise.

My mechanic checked the fan relays, fuses and wiring and all appear to be fine. I had my mechanic check the fan operation with his scan tool. The drivers side turns on when commanded as does the passenger side. However, when both are supposed to operate at the same time (high speed) for some reason the drivers side fan turns off?? Does this sound tune related? Can someone point me in the right direction?

I understand that at low settings they operate in series and when high speed is called upon, they operate in parallel. Which relay is the ground source for the drivers side fan in high speed mode, the third fan relay? Could it be that the relays are all fine along with the fuses but the contact points are weak? What can I do to make a better connection, bend the contact tabs inwards slightly?

I'm leaning towards a bad relay/bad relay connection causing a bad ground.

I would appreciate any input I can get on the fan issue.
Thanks

 

Here's the diagram for my 99..should be close(if not the same) for yours:

http://www.flickr.com/photos/1545929...57198/sizes/l/

 

Thanks for the diagram!

So according to the diagram, the first relay I should check is Fan3 relay 44 as I suspected. I get the car back tomorrow or Saturday morning and will get to the bottom of this.

Does my logic make sense in that it must be a relay or relay connection?

 

This is right out of the 2003 Service Manual:

Cooling System Description and Operation
Cooling Fan Control



The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.

The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

 

You mention that your temps steadily rise. Do they ever stop? What temps are they getting to?

 

The temps (coolant) run consistently at 180-190 when cruising. If I leave the car idiling for any length of time they steadily rise until the coolant overheat warning comes on. The oil was just changed (no coolant found in it). The coolant was also flushed (no oil found in it). I have a feeling the problem lies in a relay. Opinions?

The weird thing is that before I got the car it was re-tuned at Synergy and the car ran for like an hour and a half with no temp problems?

 

I ordered up the relay today but won't get it until Wednesday. Does anyone else have any suggestions in the mean time? Bill Curlee.....

 

I'm not Bill Curlee, but I did stay at a Holiday Inn last night .....

Relay 44 sure looks like it is the culprit .... OR the G102 ground from Relay 44 .... did you check that the ground connection is good ?? If the relay is switching correctly but the ground is bad that will prevent the left fan running in high.

In the schematic the switches inside relay 44 are set for LOW speed mode. Notice that if 44 switches to HIGH the power flow goes out connector pin F11 on circuit 250 to ground G102 ...... check that part of the circuit.

It's either the ground at G102 or Relay 44.

 

I will check G102 as that was the other suspected culprit in my mind. I am determined to get this issue resolved and should be able to do so by Wednesday at the latest!

Thanks again for your help!

Tyler

 

Originally Posted by BlackZ06
I'm not Bill Curlee, but I did stay at a Holiday Inn last night .....


Mr BlackZ06, That's funny. Sometimes I read your post just to get a laugh for the day. The plus is you're a good education for all of us.

And so is Bill!

 

Well,

after consulting with many members and studying the schematic's, I narrowed the problem down to relay number 44 or ground g102. I replaced relay 44 today and it looks like it worked! Both fans kick in and the highest temp I saw was 199. After it hit 199, it started to cool down to 194 when left idiling for 15 minutes. I have been advised by another member of a mod I can do to the front air dam to lower temps further which I will try out this weekend.

Thanks to everyone that helped or offered to help, especially lucky131969 and BlackZ06 ! I can now fully enjoy this car!

On a side note, I've never had so many idiots want to race me. I don't street race at all but I had at least 3 ricers in a matter of 5 miles want to race. I just laughed and kept driving!

Thanks again,

Tyler

 

Great troubleshooting! I pretty much have the same setup as you, and that's exactly where mine runs.. 194 degrees.

 

Hey thanks man! You were a huge help providing the schematics and such. I noticed the rad is a bit dirty near the bottom so I'll either wash it out or use comperssed air. Which would you use? I'm leaning towards the compressed air.

Good to hear that it's running at pretty much the same temps as yours. The only reason it saw 199 is because I was..ahem..driving in a spirited manner.

Thanks again,

Tyler

P.S. This is why I love this forum, so many guys willing to lend a hand for a fellow enthusiast!