Chrysler Repair: vehicle overheats and no air conditioning, drb scan tool, interference module

Question
Roland, Vehicle is a 2004 Dodge stratus. I know it is not a Chrysler but any info you can send my way I would appreciate it. The vehicle overheats and no a/c. 102000 miles.  The vehicle was brought to dealer & my friend hooked it to a DRB scan tool. He said the radiator fans did not operate. Stated that the DRB made the fan relays click but a buze noise is comming from around the intake manifold and eng.fan motors not operating. States the a/c compressor is not engaging, states the drb was hooked to it and the a/c relay clicked on, also a buze noise form the intake manifold area, but the a/c compresor is not engaging. Stated it was just a fuse and gave car back to me. But the problems still exists. no engine fans operate and no a/c compressor will engage at any time. Any suggestions ?
Bob


Answer
Hi Bob,
It sounds to me like the friend likes to play with the DRB but doesn't want to really find out the reason for your problems, maybe it's a fascination with the 'bells and whistles'.
The buzzing noise I suspect (but would need to verify on my '89 car using a DRB II which is the earlier version of what was used on your 2004) was coming from the engine controller which is called into service by the DRB test. So that is probably irrelevant.
The radiator fans need to have the relays click, but it also needs power to switch on, and the relay needs to have good contacts inside of them to pass that power to the fans. The fans need to be functional as does the radiofrequency interference module, and then the wires between them have to be patent. If it is a fuse, it would be a 40 amp fuse located in the power distribution center, a narrow box with a lid under the hood near the battery. So check any 40 amp fuse you can find (in the '96 model it is fuse #19). Then I would suggest that you use a pair of fairly heavy gauge (similar in gauge to those used in the wires that go to the fans) to jump from the two battery posts to two of the pins on the three pin plug at the fans, jumping to the side of the connector that goes to the fans (not the side that is coming to the fans from the relays).
Specifically jump the  +post to one outside pin (the one with the yellow/violet wire) and the -post to the other outside pin (with the black wire) and see if the high speed fan moves. If not then try the +post to the dark green/light green wire on the middle pin of the connector. If that doesn't work then jump to each motor directly, by- passing the rfi module. If the fans work, then replace the rfi module, if not then replace the fans. If the fans and the rfi seem o.k., then check the ground wire from the rfi to the nearby body bolt that provide the return to the -post.
On the A/C clutch, it too need power from the same 40 amp fuse that is used by the fans. So that may well be why neither the fans nor the A/C clutch are working. Other wise it is the same process, apply a 12v jump to the clutch at its disconnect plug (2 wire plug but only 1 wire used) to see if jumping 12V from the +post makes it engage or not. If not, then the clutch is no good, if it does and the 40 amp fuse is o.k. then the internal contacts of the relay must be corroded.
Let me know what you find out.
Roland