rfhaney

I have a 1988 F150 with 5.0L engine, 2WD, AOD transmission, and cruise control.

My horn and cruise control both have stopped working, and I've discovered that a two-way and possibly a three-way short has occurred between the heavy-gauge sheet metal cone and the two non-ground connectors under the steering wheel cover. I've examined the wiring diagram in the Haynes manual, and it looks like I need to do some diagnostics involving the horn relay and the cruise control amplifier.

Does anyone know where these two things are located?

sylver91

I think the amplifier is under the RH side of the steering column and the horn relay is attached to it, but i believe your problem may be a ground issue. I'd keep mapping that diagram you have and keep looking.

sylver91

Locations

Just call me Sean

iTrader: (1)

I think you should check the clock spring.

rfhaney

Thanks, sylver91, for the diagrams. They look like they ought to be a lot of help, but I just don't recognize any of the stuff in the overall diagram. Also, I have an automatic transmission, specifically an AOD transmission. The overall diagram points out a couple of clutch switches, but the only clutches I know of on my truck are the fan clutch and the A/C compressor clutch. So I'm wondering if the overall diagram is relevant to my truck.

The area under my dash near the steering column appears to be very neat-looking and not very congested. And a bit over to the right it looks like there is a lot of stuff neatly, tightly, and compactly packed under the dash, and I've gotten the impression that the RABS computer module is there also. But even that stuff looks too neat in comparison to the mass of wires displayed in the overall diagram.

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I did a couple of tests on my horn circuitry.

First of all, I measured the resistance between the steering column under the horn pad and a grounding bolt under the hood on the left fender. The resistance was 39 ohms and still climbing 0.1 ohm by 0.1 ohm after about a minute or two.

The 39 ohms seems like it could be an issue. Conceivably that could be resistance in the grounding slip-ring (aka "clock spring") and could perhaps cause a problem.

Then I attached a jumper across the connector terminals for the horn button and also simultaneously connected the ground side to the grounding bolt under the hood. No horn sounded. So it seems likely that there is an open in the relay coil circuit between its terminal under the horn pad and fuse #16, or else there is an open in the relay's "secondary" circuit connecting to the horns. My best guess is that the horn relay's coil is simply burnt out.

This also seems to confirm that cruise control amplifier is not involved in the non-functioning of the horn. This seems to be encouraging because the cruise control amplifier seems to be much like a multi-pin-out computer of sorts and could be expensive to replace.

But I need to find the horn relay and test it specifically to be sure that the horn relay is what needs to be replaced.

It also seems likely that the replacement of the horn relay will also restore the cruise control operation because the push-button switches for cruise control are powered through the coil of the horn relay.

Just call me Sean

iTrader: (1)

The horn has nothing to do with the cruise control. Fixing the horn relay would not fix the cruise control. The clock spring is what these two items have in common, the most common fix for your problem. Put down the tester and pull the steering wheel.

rfhaney

I removed the steering wheel and looked at what I would call a "clockspring assembly". It has several intricate, delicate-looking parts, including two spring-loaded small copper bushing rods that ride each on its own slip-ring -- two visible slip-rings total at the back side of the steering wheel. The electrical diagram in the Haynes manual indicated three slip rings total, including one for the ground connection, which evidently is via the steering shaft. I suppose there might be another one for the ground hidden at the bottom of the assembly, or perhaps it is located in another "compartment" further down the steering column.

Anyway, one of the two visible bushing rods has a broken plastic support so that the rod wobbles and will lean way over, and the rod probably fails to make contact at least some of the time, if not generally all of the time. It's a puzzle how that plastic support could have gotten broken.

I guess I probably need to buy a whole clockspring assembly at a Ford dealer; no parts store I've consulted carries anything of the sort.

But I'm wondering about that third slip-ring I did not see under the steering wheel. As long as I did not see it, I'm wondering if it too might be damaged.

Or could the damaged rod/support that I saw alone account for the non-operation of both the horn and the cruise control? It looks like it probably is not the ground "slip-ring" arrangement that the Haynes manual shows in its wiring diagram.

klricks

If he has something like my '86 then the CC gets its power through coil in the horn relay. So if the relay coil is open then the CC will not operate at all.

Here is a wiring diagram.


http://img18.imageshack.us/img18/2041/cchorn.jpg


.

klricks

1st ring is for the power from the horn relay coil and is HOT +12V at all times. If not check the relay and fuse.
2nd ring is ground.
3rd ring goes to the CC amp.


Here is a diagram:
http://img580.imageshack.us/img580/8806/15989572.jpg

Also refer to the other diagram I posted above.


.

rfhaney

PARTIALLY REVISED: See "REVISED" section below.

I don't know which slip ring is "1st" and which is "2nd", etc. Are you counting from the inside or from the outside? Which one is innermost & which one is outermost?

I went ahead and ordered a switch assembly from the local Ford dealer. It's a bit costly, but I should have a horn and cruise control again. And hopefully my turn signal will turn off automatically.

After I got back home I pulled the steering wheel again and have partially removed the switch assembly.

First of all, I should say that I see only two slip rings and only two corresponding spring-loaded small copper rod bushings. The likely ground wire clips to one of the two threaded holes for pulling the steering wheel.

So where is the third slip ring? Or is the Haynes' wiring diagram mistaken in that regard? I noticed that the color codes in the Haynes' wiring diagram do not agree with the colors on the wires -- at least the wire to the cruise control amplifier. So maybe the Haynes wiring diagram is just supposed to be a general idea and not necessarily an exact representation??? I suppose Ford may have changed things from year to year for the period covered by that diagram (1987 to 1989).

By the way, the wire connectors to both of the two visible rod bushings are broken where they attach to the rod bushings.

I've also figured out how the turn signal is supposed to shut off. I've always had to manually shut off my turn signals. I can only guess that someone who pulled the steering wheel before I bought the truck may have mis-oriented the little black ring that's suppose to trip the turn signal plastic levers to shut the signal off.

I also tried to figure out how I'm going to remove the present switch assembly and install the new one.

REVISED:

Oh Wow! I see that the Haynes manual has removal and installation info after all. I got the impression that the manual was not going to say anything about this because of its advice about cruise control repairs.

I see that I'm going to need to find out about the availability of a "wire terminal removal tool".

But one thing about the instructions puzzles me. The manual says "Remove the steering column shroud and instrument panel opening cover." I'm not sure what the steering column shroud is, but I guess I can probably figure out what is meant by the "instrument panel opening cover" when I go out and take another close look.

As for the "steering column shroud", it looked like there were at least two things that could be called a "steering column shroud". Let's call them upper and lower shroud. I tried removing the three screws behind the turn-signal/hazard switch to loosen the upper shroud. It looked like those three screws are key to removing that upper shroud. But the upper shroud was still stuck in place, and I could see no other fasteners that needed to be removed in order to remove that upper shroud.

I'm hoping that I can identify the "instrument panel opening cover" and remove it and then maybe that will expose more fasteners that need to be removed. Let's hope it's fairly obvious when I get into it again.

Before I found the Haynes manual instructions, I already disconnected the connector and tried to thread the cable up through the cylindrical steering covers. Well, it looks like I need to remove the wires from the connector. But it's puzzling why the connector is curved. I guess maybe Ford designed it that way to make it unique and/or obvious what connector it is.

THIS PART OF THE POST STAYS BASICALLY THE SAME:

Another thing: How do I get the connectors reconnected completely? I've figured out how to pry the connectors apart with various sizes of screwdrivers. But getting the connectors reconnected completely is not easy. The biggest problem is that there is just not much wiggle room to get in there. I have to do all sorts of contortions for access. My best idea so far is to get a larger pair of slip-lock pliers and use folded paper towels for padding against the wires coming out of the ends of the connectors. Just clamp down to squeeze the connectors together with the pliers.

Any better ideas? Will some sort of lube improve things much?