“Knowledge is power” is an old saying. “Knowledge is power, but enthusiasm pulls the switch” is a saying of uncertain authorship.
 
“‘Knowledge is power, but enthusiasm is the spark.’ — Bob Larranaga” was published in the book Calling It a Day: Daily Meditations for Workaholics by Robert D. Larranaga.
 
“‘Knowledge is power, but enthusiasm pulls the switch.’ — IVERN BALL IN NATIONAL ENQUIRER” was printed in a 1995 book published by The Reader’s Digest.
 
“Knowledge is power and enthusiasm pulls the switch.—Steve Droke” was posted on the newsgroup alt.quotations on October 27, 1998.
 
   
Wikipedia: Scientia potentia est
The phrase “scientia potentia est” (or “scientia est potentia” or also “scientia potestas est”) is a Latin aphorism meaning “knowledge is power”. It is commonly attributed to Sir Francis Bacon, although there is no known occurrence of this precise phrase in Bacon’s English or Latin writings. However, the expression “ipsa scientia potestas est” (“knowledge itself is power”) occurs in Bacon’s Meditationes Sacrae (1597). The exact phrase “scientia potentia est” was written for the first time in the 1668 version of the work Leviathan by Thomas Hobbes, who was secretary to Bacon as a young man.
 
The related phrase “sapientia est potentia” is often translated as “wisdom is power”.
   
Google Books
Calling It a Day:
Daily Meditations for Workaholics
By Robert D. Larranaga
San Francisco, CA: Harper & Row
1990
Pg. ?:
“Knowledge is power, but enthusiasm is the spark.” — Bob Larranaga
 
4 April 1995, Daily World (Opelousas, LA), “Horoscopes” by Patric Walker, pg. 12, col. 4:
Knowledge is power, but enthusiasm provides the spark.
   
Google Books
The Reader’s Digest Word Power® Quiz Book:
Over 1,000 Word Challenges from America’s Most Popular Magazine
Pleasantville, NY: Reader’s Digest Association
1995
Pg. 37:
Knowledge is power, but enthusiasm pulls the switch.* — IVERN BALL IN NATIONAL ENQUIRER
 
15 May 1996, Vital Speeches of the Day (New York, NY), “Motivating the motivators” by Richard L. Weaver, pg. 466:
Extroversion often comes across as enthusiasm. Knowledge is power, but enthusiasm pulls the switch!
     
15 February 1998, Vital Speeches of the Day *New York, NY), “Tips for effective leadership: World class leadership for women” by Julie Hughes Jones, pg. 281:
Knowledge may be power but enthusiasm pulls the switch. The level of enthusiasm of a group rises no higher than the enthusiasm of the leader.
 
Google Groups: alt.quotations
thought for today, 3/3/98
George Osner
3/3/98
“Knowledge is power, but enthusiasm throws the switch.”
>>>Ivern Ball
     
Google Groups: alt.quotations
School and Education
Quote Lady
10/27/98
(...)
Knowledge is power and enthusiasm pulls the switch.—Steve Droke
 
Google Groups: alt.quotations
Help, please with author
Quote Lady
2/2/99
I have the following quote: Knowledge is power and enthusiasm pulls the switch.—Steve Droke.
 
What I am trying to find out, is who Steve Droke is.  Please email me at .(JavaScript must be enabled to view this email address), since I am unable to get on the newsgroup very often.
 
Google Groups: akr.jobs
Knowledge is power, but enthusiasm is the spark.—Bob Larranaga
Jeff Iverson
11/27/01
Home based business opportunities abound on the Internet.
 
Google Groups: alt.quotations
Great Quotes on Enthusiasm
MarkArbou
10/28/03
(...)
“Knowledge is power, but enthusiasm pulls the switch.”
—-Ivern Ball
     
Quora
Ivern Ball is quoted as saying, “Knowledge is power, but enthusiasm pulls the switch.” It’s a great quote, and you’ll find it used all over the web, but who is Ivern Ball?
Lee Ballentine, Poet, editor, publisher, reviewer
Written Sep 7, 2016
Ivern Ball (1926–1992) seems to have been an amateur writer who had a great talent for aphorisms. She was born in Arkansas but also lived in Texas. It’s a little unclear how her “one liners” became so widely known. Here are a few of her best bon mots