From: John De Armond Newsgroups: rec.outdoors.rv-travel Subject: Re: Ford Cruise Control Recall Experience Date: Tue, 18 Sep 2007 01:05:14 -0400 Message-ID: <4tlue39e2m261fi4vtccikgjhp6cf2oaqg@4ax.com> On Mon, 17 Sep 2007 20:25:46 -0700, "Kevin W. Miller" <i09172strudelyahoo.com> wrote: >> Someone said a Hobbs pressure switch would be a real easy fix. >> >> Do I just go to Napa and ask for a "Hobbs pressure switch" then take >> it home and install it where that switch is now? Is the fix as >> simple as that? >> >> Will the wiring harness plug into the back of the "Hobbs pressure >> switch"? Will the cruise control work the same way it does now? No. Hobbs is a brand name. I see that they've been snarfed up by Honeywell. http://content.honeywell.com/sensing/hss/hobbscorp/catswitch.asp Hobbs made its name in aviation. AFIK, they invented the small, sealed, self-contained snap-action switch. Most aviation types use "Hobbs" as a generic term for pressure switch. The photo on that page is the classic switch. Hobbs also makes automotive switches. That cruise control switch may very well be a Hobbs but it isn't the general purpose switch that your advisor was referring to. Brake line switches are very specialized. First, they have to be compatible with brake fluid. That rules out ordinary rubber parts. Second, it must operate with very little fluid, lest it make the brake pedal soft or extend its travel. Third, it must fail safe. If the diaphragm ruptures it must not leak brake fluid or else the brakes could fail. Forth, the fluid fitting has to match the application. Cars usually use an SAE spec straight thread fitting with a gasket and not NPT. Hobbs switches are also very expensive. I bet that the one piece price of that switch in the photograph is at least $30 and probably closer to $50. The switch shown in Kevin's photo is a standard off the shelf automotive hydraulic brake light switch. I'd be surprised if it cost more than $10 at the local auto parts emporium. Buying a replacement part will almost surely fix the problem that is the subject of the recall. The problem is most likely only with one or a few production lots. Maybe they crimped the housing too tight and cracked the plastic or something like that. Aftermarket parts seldom come from the same place as OEM parts so the replacement will almost surely be a different brand. If the same brand then surely a different lot. Installing it involves nothing more than unscrewing the old one and screwing in the new one. There'll be a little air in the switch body but a few pumps of the brake pedal will work the air out and out the master cylinder vent. >I've put a picture of mine here: > >
> >Mine is still stock and I just received the recall notice yesterday. I'm not >sure that changing the pressure switch is a great solution either. The >pronlem is that, if it ever did leak, it still poses a fire risk as the wire >is always hot and could be shorted by the fluid. I think the fuse idea is a >good one but I wouldn't know what amperage of fuse to use. Maybe start with >a 5 amp? Brake fluid is non-conductive so it can't short out and start a fire. There are only two risks that I can think of. One would be brake fluid squirting out of a defective switch and hitting the exhaust manifold. The stuff DOES burn. Second, if the switch disintegrated and the connector swung free it might hit something grounded and short the wire to ground. The wire almost surely is fuse-protected in the fuse box. I didn't pay attention to the recall details but almost surely, scenario number one is the source of the alleged fire hazard. It's hard to imagine a short to ground causing a fire before the fuse blows. If that switch only inputs a signal to the cruise control (almost surely the case given the small wire size in your photo) then the current flow will only be a few (hundred maybe) milliamps. Anything from a 1 amp fuse on up would do. John