Restoring - General discussions that span across many different groups of years and models > Misc Items
Headlight Change TSB Article
J_Speegle:
A recent discussion in the Boss section brought up the subject of when the design of the headlights changed for Mustangs. Since this applies to all Mustangs I choose to post the meat of the TSB article here so that it could be easier found by members in the future and to share the information
Published in a mid March 1972 TSB
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
NEW HEADLAMP BULBS
1972 ALL CAR LINES
New headlamp bulbs were installed on all passenger vehicles built January 3,1972, and later. The wattage of the 5-3/4 inch lamp (low beam) and the 7-inch lamp (hi & low beam) has been increased. The Mustang, Cougar, Maverick, Comet and Pinto vehicles required changes to the wiring harnesses and/or components to accommodate the new bulbs. The Lincoln, Torino and Montego will have an upgraded charging system and components due to the new bulb. Only the Ford, Mercury, Thunderbird and Mark lV harness and components remain unchanged with the new headlight bulbs. lf the new high wattage bulbs are used on vehicles built before January 3, 1972, it is possible to draw more current on some vehicles than the alternator is capable of putting out, thereby discharging the battery and creating a no-start condition. ln addition, on cars with 7-inch headlamp bulbs, the higher wattage bulbs may cause the headlamp switch circuit breaker to operate. lt is imperative that only the appropriate specified headlamp bulbs be used when replacements are made. Refer to the following chart for bulb identification.
NOTE: The new bulbs will have 1/8 inch flutes for positive identification in comparison to the preceding bulbs having 1/4 inch wide flutes as shown in Fig. 14.
67gtasanjose:
--- Quote from: J_Speegle on March 08, 2016, 11:19:12 PM ---
... ln addition, on cars with 7-inch headlamp bulbs, the higher wattage bulbs may cause the headlamp switch circuit breaker to operate. lt is imperative that only the appropriate specified headlamp bulbs be used when replacements are made.
--- End quote ---
A VERY GOOD REASON TO BE PARTICULAR TO YOUR HEADLAMP BULB SELECTION!
The "very common replacements" in today's market can cause many issues on a Driver Car.
WT8095:
The additional 20W (10W per headlight) at a nominal 12V works out to a total additional current draw of 1.7A.
67gtasanjose:
--- Quote from: WT8095 on March 09, 2016, 09:11:49 AM ---The additional 20W (10W per headlight) at a nominal 12V works out to a total additional current draw of 1.7A.
--- End quote ---
Dave, I'm not sure I understand the intent of your calculations. Are you suggesting the Ford Engineers may have overreacted? Maybe the basic "draw" isn't enough to affect safety or satisfactory performance of a mild 38 amp alternator? (pertaining to: if you simply use the later versions of the day)
My message was more about adding aftermarket Halogen Reproductions onto driver cars WITHOUT DOING MODIFICATIONS TO WIRING and/or SWITCHES.
Since we are Concours, by definition, I'm suggesting it is a little bit more than "just looking ('sorta') correct" (e.g. Drake reproductions)
67gta289:
My interpretation of Dave's calculation is that the additional draw of 1.7 amps (total 10A instead of 8.3 @ 12V) could be enough to cause the headlamp circuit breaker to trip the light off. It is not uncommon to have an all original car to have low beam lights that cycle on and off as the circuit breaker trips, cools off, then trips again.
This is also what Ford says in the TSB when they mention the need for upgrades if higher wattage bulbs are used.
Now the question is, what do the current repros draw?
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