back when I was 17 and was working as a helper, the boss tells me to go on a service call (never ran a call before this) because all the service guys were swamped, says its no big deal just a oil furnace and just to take a look. So I get there and it runs but no fire so I start checking it out wanting to impress the boss by getting this thing running. I have the transformer layed open and place a screwdriver across the terminals and it has a good spark, so I get my face down there thinking I can look inside and see the fuel spray (I had no clue what I was doing) and I lay my cheek across the transformer springs. It felt like I got hit in the head with a baseball bat, the homeowner woke me up when she didnt hear anything in the basement after awhile. Ever since then my short term memory is horrible.
Furnace is basement room with washer and dryer next to it. Got 'tickled' by dryer when I bent over it to follow condensate drain line. Ok, small problem here, will tell H.O. later. Back to furnace, got tickled a little more. Shut off breaker and checked switch on side of furnace and blower door switch, seem ok. but got tickled again. Put things back on, no wires touching housings, reset breaker and ran blower, hmmm, slow start, low rpm. Then checked, got tickled after putting blower door on and resetting breaker again--was the right breaker each time--then took a good one when I grabbed the top panel in each hand and went to put it in place... Went arm to arm this time. I told HO, that was it--he needs an electrician to check out his breaker panel, a new blower motor, and should consider replacing his 25 yr old furnace and AC.
After leaving, I wondered if the blower motor had a short but if it was shorting, I would not have gotten buzzed when the unit was off and the blower did come on with a call for cool or jumpering R and G. Company policy is we don't go into breaker panels---just as well.