Bill56

I am looking for the schematic for cooling fan 1 for an 03 Impala with a 3.8 engine. I am getting an error code indicating a problem with the circuit of cooling fan 1. The 25A fuse for cooling fan 1 has blown several times. The problem started on the 1st 90+ degree day while in bumper to bumper traffic. Engine temp was running ~200 deg when the check engine light came on. Temp spiked 20 deg and gradually climbed into the red. Car runs normally when temp drops back to the 60s & 70s. This problem started at the end of last summer and went away when the weather cooled. I have swapped the relay with others in known good circuits with no change to either circuit.

Mike Sigmond

Here ya go Welcome the the forum!

Bill56

Thank you. Before I start troubleshooting, is there a common point of failure or defective component?

Mike Sigmond

No problem, the fan could be bad. Is your coolant nice and full with no air in the system?

Lets see if any of the ASE guys here can chime in on the common problems.

HotSauce6226

Where in the ***** did you find that..

BTW who volenteers to teach me how to read schematics?

Bill56

The coolant is full, no air bubbles in the system that I can tell. Reservoir is at "full-hot" so I think I am OK with coolant. Looks like the fans have a high & low speed...didn't realize that. My assumption is the "left" fan is the driver side since the "right" fan stops when the Fan 1 fuse blows.

Mike Sigmond

Dude , anytime. I can AIM you sometime and give you some basic sheets to explain it all, its what I did for 15 years , reading them for complex computers systems for huge amusement rides, roller coasters, etc.. I know them prety well and have access to a NAARSO www.naarso.com database that includes cars all makes and models. Its for techs to get factory info on equiptment, My membership is expired so I cant inspect and repair at the moment but I still have a login and password

in2pro

A schematic is like a "pipe or plumbing view" a circuit

Google "how to read schematics" and you will find lots of helpful items, most will cover electronics but there are also mechanical, plumbing, electrical diagrams too. keep in mind there is a difference between an electronics and electrical schematic, the electrical one is probably more helpful in automotive trobleshooting, the electronic ones go deeper into the actual device.

Mike Sigmond

Here is one for understanding most symbols for automotive schematics...

Bill56

Still have not found the source of the problem. The check engine light came on in cool weather then went out a couple of days later. The 25A fan 1 fuse did not blow. I am not naive enough to think the problem went away.

I found some discussion of a similar problem at http://www.justanswer.com/questions/...-fans-One-runs

The article describes the circuit logic (which I understand) and provides the temps that cause the various relay actions. Since the temps are far in excess of my temp gauge range, I would like to know what the temp points are for the low speed fans to come on and for the high speed fans to come on for the 3.8L engine with dual heat zones.
Thanks