Solving Diagnostic Problems This is a web site where questions can be posted by members with diag- nostic problems. Other members post “fixes” based on their personal expe- riences. There are very strict rules re- lated with posting questions so that time is not wasted sourcing answers which can be found in manuals, TSBs, etc. Membership is required— but it is free! Membership information can be found at: http://www.iatn.net. Posting guidelines can be found at: http:// www.iatn.net/guide.html. The majority of the electrical-re- lated posts deal with diagnostic prob- lems. These posts do not directly re- late to rebuilding but will help you with customers’ problems. Following is some of the informa- tion gathered since the last issue of the Exchange. Charging Systems VEHICLE: 1992 Lexus 300 EN- GINE: 3.01 POST: The alternator and battery have been replaced in this vehicle. The alternator is rated for 80 amps. Any- thing off idle, with the light or a/c on, this alternator is pushing 60 to 80 amps. Needless to say, the battery acid is boiling out of the battery. Why is the maximum amperage being pushed all the time? FIX: The problem was traced to a broken wire in the alternator harness. The small white wire must be ‘hot’ all the time. If not, the alternator will charge at full output on a constant ba- sis. VEHICLE: 1990 Chevrolet 1500 Pickup ENGINE: 5.71 POST: The charg- ing system on this vehicle works fine until the transmission shifts into over- drive. When this happens, the alterna- tor stops charging. FIX: The wiring harness was pinched between the bell housing and the engine. This was a very hard prob- lem to diagnose and it was only after the customer informed us ofa rebuilt transmission installation (three months prior) that the problem was traced. VEHICLE: 1993 Jeep Cherokee ENGINE: 4.01 POST: This vehicle dies while driv- ing and will start back up immediately. All wires have been traced and no loose connections can be found. The fuel pump was replaced one week ago. FIX: The problem was traced to abad alternator. The alternator would spike and the pcm would temporarily shut down causing the vehicle to die. VEHICLE: 1992 Pontiac Sunbird ENGINE: 2.01 POST: This vehicle came to our shop after four alternators and two batteries had been installed over a two- year period. There is no apparent ex- cessive draw and no voltage drops in the wiring. FIX: The belt tensioner was the problem. The tensioner was not keep- ing the belt tight and therefore the al- ternator was never charging correctly. Starting Systems VEHICLE: 1993 Volkswagen Eurovan ENGINE: 2.51 POST: This vehicle was towed in with a ‘no-start’ situa- tion. The power windows are stuck down and fuse no. 141s blown. There is no power to the starter solenoid e1- ther. FIX: The problem was traced to deteriorated wires in the rubber boot DECEMBER, 1999 going to the left door. VEHICLE: 1995 Chevrolet Cava- lier ENGINE: 2.21 POST: This vehicle came in as a ‘no start.’ First check found a bad battery. This was replaced but there is still no power to the starter. The vehicle can be started with a remote starter and will run fine. FIX: The problem was traced to a faulty ignition switch. VEHICLE: 1993 Eagle Vision EN- GINE: 3.51 POST: This vehicle has an intermit- tent ‘no start’ situation. When the key is engaged, the dash lights, radio, etc. work but the starter will not engage. FIX: The ignition switch was not supplying power to the starter solenoid. VEHICLE: 1995 Jeep Grand Cherokee ENGINE: 4.01 POST: This vehicle came in with a complaint of the starter staying engaged intermittently. FIX: The problem was found to be between the PDC and the starter. A simple voltage drop test found the ground wire from the starter relay to the fender showed 3.5 volts drop. Removing the wire found corrosion under the connection. Other Systems VEHICLE: 1988 Lincoln Mark VII ENGINE: 5.01 POST: With the vehicle running and in park, the speedometer reads 85 to 10 to 60 to 145, etc. It jumps all over. While driving, the same erratic patterns appear but the odometer works. FIX: The alternator was faulty. Replacing the unit with a reman solved the problem. VEHICLE: 1985 Mercedes 230E ENGINE: 2.31 POST: The RS and ABS light come on intermittently. FIX: The problem was traced to a Page 1 of 2