Technical Knowledge

I have driven my 1966 TR4A for many years with nothing but the bare minimum in maintenance. Recently, I decided to park it for a couple of months and commence on some repairs I had been putting off. First choice was the horn, which had not worked In several years!

With an inexpensive voltmeter, it was easy to discover that there were 12 volts direct current (dc) to the horn, but the ground was missing. The steering wheel was very sloppy as it moved side to side and up and down in the steering column. I believed this was the reason for the lack of ground to the horn button. After reading a steering column tip in one of the excellently illustrated Moss catalogs, I placed an order for steering column bushings (#525-020), and since I was going to replace the two bushings, I decided to completely rebuild the steering column—black gloss paint to eliminate 32 years of wear and tear, new column mounting felt, two steering shaft rubber couplings and new grounding straps, and, lest I forget, a grommet to seal the engine comportment feed through.

All the pieces came together very easily and I had a nice solid steering wheel with no play! All that was left was to slip the horn brush (which looks like small 3″ pencil) back into position, and pop the horn button back into place. Now came the test: I pushed the horn button and, OH NO! I thought to myself as no sound emerged. Everything went together so easily—what could be wrong?

I got out my inexpensive voltmeter and started back-tracking to find the missing voltage. The newly fixed ground was there and the horn button was good. But what had happened to the +12v dc? It was present when I started the rebuild! I checked the quick disconnect connection where the purple wire leaves the steering column. Still no voltage. Okay, time to pull out the electrical schematic to see where the horn voltage is supplied from. The schematic showed a fuse, so I checked the fuse box only to find that everything was good, which didn’t make sense.

The schematic also showed a purple wire up to the fuse box, but the fuse box wire colors did not match. A little more investigation and I found the in-line fuse by the passenger side horn. The fuse was okay, but there was residue on the fuse holder contacts, which easily came off with a little steel wool. I checked for voltage at the horn brush and it was now there. Great! Pop the horn button back in and all complete. However, still no sound as I pressed the horn button!

All the needed ingredients for a correctly working horn were there (ground, voltage, and horn button). After disconnecting the battery, I used a combination square to check the physical dimensions from the horn brush (supplies +12 vdc) to the steering column rim (where the horn button rests) and also checked the depth of the electrical contact on the horn button which mates to the horn brush. There was a 1/16″ gap between the horn button electrical contact and the horn brush! My steering column had been so sloppy before the rebuild that the electrical contact on the horn brush was worn down too far to bridge the distance between the steering column supply and the horn button!

A close inspection of the horn brush revealed that it is composed of solder, so to eliminate the possibility of excessive wear in future, I created a new, and higher, solder bull at the end of the horn brush. Putting the pieces together, the horn now functioned flawlessly—and even though I rarely use it, sometimes you just have to toot your own horn.

—Robert White, Costa Mesa, California.

FITTING THE PULLEY HUB ON A TR4 ENGINE

When, for whatever reason, the timing chain cover must be removed and replaced, especially when the engine is still in the car, remembering the following will make the job easier. The Woodruff key for the pulley hub is INSIDE the timing chain cover.

1. Before removing the pulley hub, ensure that the #1 piston is at bottom dead center. This will place the Woodruff key in the most advantageous position at the top of the crankshaft.

2. On reassembly, if it is discovered that the Woodruff key is such a loose fit in the crankshaft that the key is dislodged on every attempt to fit the pulley hub, invariably fulling into the timing chain cover (which necessitates removal of the cover once again!), here’s a solution.

Simply lay the Woodruff key on a hard flat surface, and with a center punch, whack a dimple into the key. The dimple will upset the metal so that the key will be a snug force fit when topped into the crankshaft recess. Then fitting the pulley hub will be a simple task, as the Woodruff key will stay in position while the hub is slid into place.

—Professor Robert Koval, Westmont, New Jersey.

(This applies to TR2-4A and probably others!—Eric Wilhelm, Moss.)