Expert: Brad Sears - 5/12/2010

Question
Hi Brad,
Have code 30 isc.  Also a/c would not turn on, so we replaced
low pressure temperature switch on back of compressor after
bypassing it and jumping the compressor which turned on. We
now have to recharge the a/c.  Are the a/c and isc connected
in some way? Does the isc have to be working for the a/c to turn on?
Thank you.
Donna

Answer
The two problems are most likely unrelated. The code 30 indicates that either the idle speed control motor is defective or that it cannot accomplish what it is commanded to do. Over the years when the idles speed control did not do what the mechanic working on the engine thought that it should do they tinkered with the idles stop, or minimum idle screw, to bring the engine to whatever idle speed they thought was correct. This minimum idle speed control should be adjusted to an idle speed of 450 RPM once the idle speed control motor has been disconnected and pulled out of the way. One point here is to not disconnect the idle speed control motor or reconnect it with the ignition turned on or the engine running. The procedure is a bit too long and complicated here but is not difficult. There are several good manuals that can be purchased covering the electronics of this car. Some are on E bay and Geezers Old Cars %26 Parts has used manuals for sale. Contact his at www.geezer34nh@yahoo.com.
Brad