Well ballasts must deliver substantially high power to your bulbs. Many are designed to deliver 'just enough' power to get the job done with little 'headroom' or cushion beyond that. In other words, most ballasts run balls out!
If the fan is still running, I suspect there MAY be a "automatic thermostat" inside killing the power to your bulbs and the fan is constantly on to help cool the unit down rapildy. As soon as your thermostat auto-resets you are back in business.
HEAT is a real killer of electronics parts and this is true for thermostats too. The bi-metals can finally fatigue from passing so much current for so long... the same is true for old house circuit breakers. With age, the breakers can trip too early. That is, a 15 amp circuit breaker will trip at ~ say 10 amps or 12 amps, again due to lots of heat passing within the circuit breakers over time.
I have seen breakers trip too soon, but never too late... that is, a 15 amp breaker tripping at 22 amps... Thank God.
AND if the manufacture used a cheap circuit breaker, there is a very good chance it will fail sooner!
Cold Solder Joints: Many times a cold solder joint is the culprit. Solder junctions should appear bright and shiny, not tarnished or dull silver and NEVER cracked. But I have SEEN bright-shiny solder junctions where the solder bonded itself to the WIRE, but NOT to a 'tab' or terminal below! This is usually due to tarnish on the tab before the soldering or where the solder iron was not held on long enough to heat the tab too. Thus, the junction may appear perfectly good, BUT the wire is actually loose on the tab underneath the wire and solder and the only thing making and keeping the connection is that the wire is wrapped around the tab.
Inside your ballast things can get so hot that if you have a cold solder joint where wires and terminals semi-junction, heat and power surges (when the ballast it turned on) can cause those connections to finally crystallize and become intermittent. OR that tab can actually blacken as the poor junction sparks from the power demands when the lamp is first turned on and as power passes through the poor junction. Tiny sparks at the bad junction can also cause a thermostat to finally trip.
PUSH ON TERMINALS: are metal push-on connectors. One end and has a sleeve or barrel where the wires are placed inside, the other end is the push-on connector. Some have plastic covers around them and some are bare metal. Once all the wires are inside, the sleeve is crushed to capture all the wire(s) inside. IF the sleeve is not crushed properly, the junction can become almost like a thermostat itself! Not good. This is especially true when there are TOO many wires inside ~ again, bad design. Instead of installing a decent terminal strip, the manufacture chooses to use the much cheaper 'tab' and they can cram too many wires inside when they do.
UNPLUG your ballast from the wall and your lamp(s). Using a bright light and magnifying glass, give CLOSE inspection to ALL parts inside. Examine every single wire junction and part looking for burnt or brown components with signs of over-heating. Pay special attention to the junctions! Gently tug on push-on connectors to assure the wires are not loose inside the sleeve. IF the push-on tab pulls off easily, use needle nose or regular pliers to gently squeeze the push-on end of the terminal tighter. Also when the terminal is disconnected, check the TAB that receives the push-on terminal and assure that it is spiffy clean! While you are at it clean out all of the dust and crap the fan blew in.
IF everything looks OK, I would buy a replacement thermostat WITH THE SAME RATINGS!
You may save some time by calling the manufacture to see if they will sell you the proper thermostat for your model? If they have seen your problem before in other ballasts, they may have replaced the inferior part with a new and better one and they just may GIVE you one?
Thermostats are WAY cheaper than buying a new ballast... that just may cure what ails you. Usually there is plenty of room inside so you won't have to find the exact (PHYSICALLY speaking) thermostat as the original, BUT the TEMP. / VOLTAGE and CURRENT ratings MUST be identical to the thermostat you are replacing! Specifications are almost always printed on the part.
Be extremely careful when you do this:
If you can 'time' the ballast failure all the better. That is, if you know your ballast fails every ten minutes. AS A TEST, you can use a alligator jumper to TEMPORARILY jumper over the thermostat terminals! Set the cover back on and use a few screws to keep the temperature to where is normally is... BE CAREFUL to NOT crush your jumper wire.
KEEPS YOUR EYES on the ballast at ALL times!!! And be ready to DISCONNECT POWER if there is ANY signs of smoke at all!
IF your ballast stays on for 30 minutes WITHOUT SMOKE, chances are that the thermostat is indeed defective. Replace it for sure. IF your ballast still fails after replacing your thermostat with a new one... call the Auto Club and have them tow your ballast away.
Google is your friend, but do be careful as some vendors greatly overprice items!
I have also seen power switches go intermittent, BUT you said your fan stays running so I highly doubt if your problem is a power switch problem.
Many many times simple repairs may bring your Frankenstein back to life!
I hope this helps many people...
I remain,
SOGLAD
