Changing Ballast Components

Assuming your ballast is hooked up right and is relatively new, the capacitor (cap) and socket are about the only things that will give you problems. They last about 5 – 10 years on avg. Igniters (ign) on the other hand (if equipped) last much longer, at about 15 – 20 years. The transformer (tran) part of the ballast will last even longer, assuming it does not have deteriorated leads or mechanical damage.

All ‘life expectancies’ are shortened buy about 30%, if the ambient temp surrounding the ballast is much higher than 110°C (230°F). All the more reason to give your ballast good venting. (This doesn’t apply to the socket)

Besides the changing of bulbs every 8 to 12 months, you need to check out following:

Checking the ballast

Polarization (ballast)

Make sure the white / black wires are where they are supposed be. Black wire to LOAD / White wire to COM power source If reversed, the ign (if equipped) may not work and the cap might wear out faster than it’s supposed too, same thing for the bulb.

Polarization (socket)

The black lead should go to the “tab” in the center of the socket and the white lead to the threaded metal. If reversed the bulb may not work or wear out faster than it’s supposed to.

Leads (cap, ign, tran and socket)

Make sure they are not loose or deteriorated. Give them a little pull as well as bend them (in the middle) at an 180 degree angel. If they feel like they are about to come loose or show cracks in the insulation, replace the component. If the lead is cracked (pic#1), shrink wrap the lead as a temporary fix till you can get a new component. Check that the socket is not cracked and make sure the fiberglass insulation is not torn up or unraveled (pic#2). If the tab looks burnt up or discolored (pic#3) replace the whole socket.

(Another thing about the socket. You know those little cardboard-like washers you get with the mogul and some medium sockets…? They are there for slack so when the socket heats up and expands, the rim of the screw holes dont chip off. That way you can mount it nice and secure without problems.)

Cap’s with leads

If the wires are off center, one wire is closer to the rim of the top of the cap. The wire closest to the rim of the cap should go to the long side of the transformer and the wire farthest from the rim should go to the short side. If the wires are not off center than any way is fine. I\’m sure it will run fine either way, but the cap may wear out faster.

Note: If at any point you notice the cap looks bulged-out, replace it ASAP.

Testing the capacitor (cap)

Things you will need: A screw driver and multiple tester.

Step one: Disconnect the cap from the transformer and discharge it

If your light was just running, wait 10 or 15 minutes. Disconnect it, then touch the leads to the metal part of the cap 2\” apart. If it does not have a metal case do so on a peace of bear metal. If you have the kind that looks like a 9V battery touch both terminals (at the same time) to a screw driver or a piece of bare metal.

Step two: Find out the UF of the cap

It should be printed somewhere on it.

Step three: Set the ohms / multiple tester to the “F” or “UF” function for ohms

Touch one probe to each terminal / lead and note the number. It should be with in 10% of what is printed on the cap.

Note: You have to keep the probes on it for a little while to get a reading.

To get percent you take the number, times point the percent you wish to know Exp: 100 x .10 = 10 (this is your ten percent of the number.)The percent added or subtracted from the number = the number at + / – the percent. If it is over / under 10% of what printed on the cap failure is soon to follow. If you get an “OL” (infinity) or close to “0” reading; reverse the + / – probes and try again. If you get the same thing your cap has crapped out.

If you suspect the ign, get a new one and try it out (you can always return it if it’s doesn’t look like it’s been used). HID capacitors and igniters can usually be bought at retail electrical supply stores for around $5 to $15 each (US).

A note about ‘buzzy ballasts:

The sound is probably the transformer plates shaking apart. The outer parts of them are only held together with that coating, over time the lacquer coating breaks apart and the plates get loose. When the transformer heats up, that stuff gets soft and the plates can move around better.

Solution:

get a new transformer
What I have done before is drill out the holes in the transformer and run some small bolts though it. That usually quiets them down.