Packard Forum Index » Post-War (1946-54)

I am looking for the mercury switch for a 1949 Packard Custom 8 coupe trunk light. The switch is a cylinder that is 3/8" long with a diameter of 3/8" also. See photo attached.
bjsgarage@earthlink.net

Attach file:

---

Size: 194.57 KB; Hits: 86

I had mine out as I thought is was toast. I shook the mercury, and could hear and feel it inside. I put a meter across the switch, and found that after tipping it if I gave it a light tap it would work. I put it back in the car and hooked it up. The parking lights have to be on so that there is power to the switch . I had to tap it a couple of times but it did work. Just my 2 cents.

It may not be a mercury switch - it may just be a rolling ball that grounds that wire. Take it out and shake it vigorously as it may have rust inside causing it to remain still. I believe my 56 is just a rolling ball.

It felt like murcury, but I gave it a hard shake for good measure. It seemed to improve it's operation.

It's a mercury switch and wears out via corrosion of the electrodes due to arcing. Shaking it works a little but not for long.

Right guys - it's a mercury switch. Mine is worn out - works intermitantly. Shaking isn't fixing it. My question is - does anyone have an extra or know of a source for a new one of similar design? James

I'll be surprised if you find a new mercury switch for automotive use. Seems like the agencies are doing their best to eliminate their use due to the hazardous waste aspect. Several programs to dispose of them when a car hits the junkyard are in effect. Someone might be able to supply a used item -- maybe even from a Packard -- but then you have the same problem of is it any better than what you have.

There are still a few small switches available for electronic use. Philmore is one brand still making them and probably available locally if you have a good electronics store nearby. To use in the Packard application you would have to fabricate some kind of housing to protect the glass envelope and make an arrangement to have the leads duplicate the original contact areas. Most if not all are longer than 3/8" -- usually 5/8 or so and about 3/16 diameter. For electronic use they also have low current capacity. The trunk light wouldn't need much but you still might have to put two in parallel.

I don't see any firm dimensions to know if two side by side could fit in some kind of plastic sleeve or tube to duplicate what is there but maybe a possibility. If not, you might be able to lay two side by side in some protective sleeve and hide them above the light and then connect the leads.intertexelectronics.com/Search.aspx?k=mercury%20switch

Thanks. I've seen these and other mercury switches on ebay. Have a lead on a used light and will persue that first. If it doesnt' pan out will try these new switches. I think they will fit under the cover. One switch style has a tab with a screw hole. Perhaps that would fit onto one of the two the existing base screw holes. Will let you know what works. But question - why do you suggest two switches in parallel?

The rating on the Philmore is 1 amp at 250VAC which using on a DC voltage will be considerably less. Would have to measure the bulb but I suspect it would be pulling several hundred milliamps and could be running at about the max safe of the switch. To avoid heating the contacts of the switch and particularly the leads I'd spread the load.

If it helps any, here's the advertised amperage draw on some common 6-volt bulbs, data from Mazda/GE:

50/51 - 0.20 amps
61/62 - 0.84
63/64 - 0.54
67/68 - 0.26
81/82 - 0.89
89/90 - 0.48