"God Bless You" says a sign pasted on an adding machine that totes up donations to the Campus Crusade for Christ. "No turning back, no turning back," sings a Southern Baptist choir "It is FUN to be saved," exults a chubby preacher at a boy's Bible camp.

Many such faces and voices of American evangelical Christianity in the slick '70s are captured with striking clarity and insight by reporter Bill Moyers on the CBS News special. "Born Again" at 10 o'clock tonight on Channel 9. This is no quickie or glib job; the hour has moments that are moving, penetrating, flabbergasting and, sometimes, frightening.

Stating that he considers himself a "born-again" soul at the outset, and naturally pegging the report to the evangelical mood of the Carter White House, Moyers encounters representatives from various Christian groups who have devised their own ways of proselytizing and enforcing moral codes.

Perhaps most in tune with their times, for better or worse, are the Madison Avenuesque prophets of "I Found It!", who go-ye-therefore with buttons and bumper stickers on a $6-million conversion mission. Former ad man Bruce Cook, spearheading the campaign, defends his "media marketeering" tactics by saying that early prophets blitzed Jerusalem" using the media of their day.

Such converts as Eldridge Cleaver and former politician Harold Hughes are interviewed. "I'd rather be a 'nut' for Christ then anything else I know of," says Hughes. Moyers refers pungently to "the most recent Amazing Grace, Chuck Colson," but Colson is not interviewed on the show because, producer Janet Roach said yesterday, "Colson has been talked to so much, and Hughes had been less public."

Moyers contrasts the drip-dry, no-pain conversion appeals made by the squeaky-clean evangelicals with the excruciating personal ordeal of old-time, down-home fundamentalism. The difference is made dramatically graphic during a justifiable invasion of privacy: a 16-year-old girl walks down a dirt road in a star-covered dress after being rebuked by a fiery minister and sobs. "Seems like everything I do don't come out right."

Perspectives are supplied by University of Chicago theologian Martin Marty. He sees deceptions in some of the new groups but has the wisdom to note a positive element, as well. "You can't have a humane world," he says, "if you can't work on the assumption that people can start over."

The program does not deal with the whole separate subject of black fundamentalist groups, but what it covers it covers very well. The script, by Moyers and Roach, might have said more, however, about the relationship between the new evangelicals and one of their chief tools, television. Like television itself, many of them preach the gospel of the easy answer.

But "Born Again" is still an exception to the television tradition of smoothing troubled waters with platitudes and amortizing conflicts by declaring all viewpoints equally valid. The refreshing thing about Moyers' work is that he does take a recognizable stand. He does not subscribe to the TV gospel of killing doubts rather than raising them.