Volvo: Dead Cruse Control on 98 V70 GLT, brain boxes, brain box

Question
QUESTION: The cruise control on my 98 V70 GLT is totally non-functional.  My Volvo dealer says it needs a new "brain box" and has been unable to obtain the part.  I can purchase replacement used "brain boxes" from a number of sources.  Is replacing that part likely to fix the cruise control?  And, most important, where is the "brain box" located and is it something a proficient amateur should be able to replace?  Thanks!

ANSWER: John,
The control unit is under the fuse cover. I have seen a couple of control units go bad, yes. Most times I get an inop cruise it is due to broken vacuum lines, or misadjusted brake switch. Any more diagnostics will require use of the scan tools to monitor the system.

---------- FOLLOW-UP ----------

QUESTION: Thanks for the prompt response.  Last night I tried pulling back on the brake pedal while driving and the cruise control works as long as the pedal is pulled back.  That sounds like a misadjusted brake switch.  Any recommendations for how to adjust it?  BTW, the dealer wanted $1,100 to replace the controller and (fortunately) was unable to locate the part.  So much for diagnostics!

Answer
John,
Most of the cruise switches just simply have threads and screw in to adjust. Some are self adjusting and need to be pushed in and allowed to return out, like a snapping action. If the switch will not adjust you can install one that has the threads. You can also add a shim to the end of the switch to aid in adjusting.