Restoring - General discussions that span across many different groups of years and models > Parts
Yellow Top Coil
markb0729:
I've had my fair share of troubles with after market ignition coils so I've been keeping my eye out for an original Yellow Top Coil that's in very good condition and/or can be cleaned up and be presentable at car shows. I'll pay more for one that is excellent condition but jeez, prices seem high to me. Anyway, I came across this coil on eBay and it looks pretty good. The coil appears to be an original yellow top coil but there is not any signs of an ink stamp. Seller says that it works but I sent a message asking if they could get me the primary and secondary resistance readings. What do you think, original? Seems to be in visually good shape and the price hasn't been bid up... yet.
Mark
Sellers Description:
FORD YELLOW TOP OR MUSTARD TOP COIL: this is a used coil for the classic Ford or Mercury, it is the yellow top. this came from an estate auction of an old Ford mechanic, it was in his desk drawer. I did have it tested and it has good spark. this coil has no ink stamp to show a part number. you classic Ford folks will have to sort that out to see if it will do the job for you. it has the dist. and bat. markings. I was told this coil was used on the Fords and Mustangs and Mercury Cougars 1965 1966 1967 1968 1969 1970 1971 1972. the buyer will pay 9.80 S&H.
Pictures:
196667Bob:
A couple of things to be aware of on your yellow top coil. First, they were first used by Ford in 1957. The earlier ones (57 to about 64) had a "bump" on them for indexing on the coil bracket (see attached picture). The later ones, from about 1965 on didn't have this bump.
As far as testing, what I normally do is after testing the primary and secondary resistances, is take my heat gun (or hair dryer if you don't have one), and bring it up to 150 degrees, which is about the operating temperature of a coil in a warmed up engine. If the resistances stay close to the "cold" coil resistances, you should be good. When the coils go bad, they usually break down under heat, and will give erratic readings.
In regard to the coils appearance, besides repainting the semi-gloss black, you can restore the yellow top if needed, using Rustoleum Satin Amber spray paint. It's very, very close to the original mustard top. Just do a careful taping job, and don't forget to tape off the Dist and Bat posts, and the inside of the "tower" where the coil wire goes.
As far as finding an original, you might check Mustangs, Etc. A couple years ago, they had a good supply of used ones that had tested (although not with the heat), at reasonable prices.
Hope this helps.
Bob
markb0729:
Bob, thanks for the info and advice. Every little bit helps. I sent off an email to Mustangs, Etc. I'll see what they say.
Mark
196667Bob:
There was a question when I looked at this Post this morning that asked, "How do you test a coil ?". It has apparently, since been removed, but since I have prepared an answer, I will still Post it, since it is a valid question.
Typically, one might see a "Coil Test Procedure" something like I have attached (from the 1957 Ford and T-Bird Shop Manual). It notes what you are testing, and why, as well as testing at normal operating temperature (as I noted previously), but it doesn't tell you how to do it. It really is a rather simple procedure.
First, you need a multimeter (Volt/Ohmmeter) capable of reading 200 ohms, and 200,000 (200K) ohms. Also a heat gun (or hair dryer if you don't have a heat gun), and a way to measure the temperature of the coil (I use an infrared thermometer). An option to the heat gun and thermometer, is to start the car (after the "cold" testing), and bring the engine up to normal operating temperature. Then disconnect all wires from the coil, including the Distributor to Coil wire. Then do the test on the hot coil.
The test procedures are as follows :
1) For Coil Primary Resistance, set the meter to the 200 ohm scale.
2) Connect the Red lead to the "Bat" (+) terminal of the Coil, and the Black lead to the "Dist" (-) terminal.
3) Record your reading (for 1965-67 Mustangs, should ideally be 1.4 to 1.54 ohms.
4) For the Coil Secondary Resistance, set the meter to the 200K scale, leave the Black lead of the meter connected to the "Dist" terminal, and move the Red lead to the Coil tower (where the wire from the Distributor was), making sure that the lead makes contact with the connection at the bottom of the tower. This reading should be somewhere between 7600 and 8800 ohms (although I have seen some used "good coils" as high as 30,000 ohms). Record your results.
5) Repeat the same tests on the Coil at operating temperature and observe if it is a steady reading. Record your results again.
6) Compare the results. If the results of the "hot Coil" vary significantly or are much lower, then the coil is breaking down when hot, and should be replaced. All results are significantly higher or lower, then it should also probably be replaced. The values shown in books are typically for "new" coils, and some differences are to be expected with old or well used coils.
You can now be labeled a "Doctor of Coil Resistology".
Hope this has helped.
Bob
J_Speegle:
Mark interesting that the one you show in your post lacks the markings between the post. Haven't really studied when that started or if it relates to the type of coil, date or other detail we have yet to discover but thought I would mention it. There are multiple applications and there are some that are slightly smaller than what was factory for our Mustangs. Bleive they were shorter by just a little
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