Junkyard Cruise from Scratch - Amplifier Mounting?

[lowspeedpursuit]

I don't know a ton about electronic logic, especially AC and converting between different types of signal. I wonder why the wiring diagrams break VSS ground out separately, then? I assumed they want a more direct path to avoid the potential for too much resistance along the common ground, but it could save trouble extending that PK/O wire if it isn't really necessary.

I think the VSS probably checks out at this point, although I still wish there was a way to test its output directly. 8000 p/mi should also be 8000 p/min @ 60mph, which gives 35/60*8000 = 4667 p/min @ 35mph. So, I feel like you should be able to divide that by 60 and measure 78Hz with a capable multimeter, but mine shows 1kHz, so I must be misunderstanding something.

Various parts will be here Wednesday. I grabbed a '94 Mustang module for $20, but I won't know if it's actually compatible inside until it gets here. Affordable green-box modules are basically hen's teeth around here at this point.
A way to test the modules would also be nice, but while I understand what they do, how exactly they work depends on the chip inside, which is kind of a black hole of information.

 

[RonD]

VSS ground wire(pink) usually is grounded in the cab where devices using it are located, vs frame or engine/trans ground
Technically all the grounds should be equal at all locations on a vehicle, real world.............usually not, lol


Useless extra info
For cruise, PPM needs to be present but not calibrated to speed
For electric speedometers, started in 1995, it did matter
The VSS signal from the trans/transfer cases were calibrated with rear axle ratio and tire size(rotations per mile), calibration was done by the changeable Driven gear on the VSS unit to calibrate MPH for speedo cable and VSS, cruise gets the same signal but has no idea what "speed" is, lol

In 1998 Ford high jacked rear axle ABS VSS and ran that 25,000ppm(approx.) signal to the GEM module which converted it to 8,000ppm using tire size only

In 2001 all transmissions(manual and auto) got an OSS(output shaft speed) sensor which was about 32,000ppm, it was connected directly to computer which had rear axle ratio and tire size
Compouter would then send out the converted 8,000ppm signal to speedometer and cruise
GEM and computer could be programmed for tire size changes and axle ratio changes as needed

In 2001 and up 4x4s, the computer would get the "heads up" when 4low was activated and it would change the ratio to make speedometer accurate in 4low

 

[lowspeedpursuit]

So, solution first: I had a bad connection where I tapped Brake On/Off (LG). That wire isn't open with the brakes released; it's grounded through another circuit, and cruise won't work without that ground. Service manual troubleshooting doesn't list that as something to check under "speed control does not work", but it's listed later under "speed will not set in system".

Since I have it, the '95 Mustang amp appears to work so far in spite of being a different board inside. I've mentioned the '93 Explorer uses F1VF-14A608-CD. The Mustang uses a redesigned F3ZF-14A608-AA:

You can see the same D9AF-14A607-A3B chip, and the other components all look basically the same as well, just moved around. I built a SPICE model of my original amp in case I had to screw around with it at some point, and I quickly verified a couple of circuits on the new amp before hooking it up. Among the pins on the IC, 1 and 24 are grounded, 13 is V+, 12 goes to Brake On/Off, 2 and 3 are jumped, and 6 is unused. The only obvious difference between the boards is that pin 1 on the big connector has reverted from an unused "cruise light" to a duplicate brake signal pin, just like it was on the older E3- and E7- boards.

In any event, it seems like there's greater amp availability than I was led to believe when I started gathering parts. It is kind of a moot point if you're grabbing everything from the same donor truck, since the servo is still pretty specific. My servo is out of a 4.0 truck with a rebuilt actuator cable, so I'll write that up at some point when I have the time.

 

[RobbieD]

Thank you for the update, and for the information. Great work!

 

[rumblecloud]

Bookmarked this thread...thanks.
I don't use cruise very often and my depth of knowledge about the system is so far below what this string is telling me ---
I've gone as far as replacing the amp several times from JY pickups (whenever I go, I just grab one if it's available).
But one day...I'll try to tackle it and this thread will be my go to.

Thanks
R

 

[lowspeedpursuit]

Cruise control is a game-changer, and I can't believe I've put up with not having it for 7 years now. Everything worked great on a real test drive, so I'll say the Mustang amp is definitely compatible.

Working on the "safety" systems, I got the Brake On-Off switch wiring finalized and routed through the clutch switch. My harness is missing the cruise pins there, and that pigtail is apparently $50 new. But, I'm already bypassing the clutch ignition interlock, so I just swapped those unused pins over to positions 3 & 4.


This leaves me with another request for better pictures: I'm trying to set up the dump valve. This is already kind of a shitshow because I've been using its hole in the firwall to run my own wires (A/C, heated seats, and now cruise), but more importantly, it mounts pretty far above the brake pedal. The first pic is the wrong truck, but it's clearer on how the valve clips in. From the same thread that showed me how the amp mounts, apparently there's this giant piece of plastic that clips to the brake pedal that I don't have:

The manual doesn't really show this part at all, and it's not considered part of the brake light switch or the pedal assembly, so I guess it's supposed to be part of the dump valve.
Has anyone got any other pictures of it, maybe even out of the truck, so I can fabricate one?

 

[RobbieD]

This leaves me with another request for better pictures: I'm trying to set up the dump valve.

See if these help. I'm not 100% sure on a '94 model; these are how it mounts in a 1990.

On this setup a metal clip holds the dump valve; it just pushes in from the top until the pedal bracket closes the valve.

You can also see the vac hose coming through the firewall in the first pic.

 

[lowspeedpursuit]

Sweet! Thank you. I think we do have the same pedal assembly, so I should be able to work something up from that.

The vac routing is interesting. I have an unused punchout in my insulation there, but I don't see a corresponding punchout in the firewall itself. I've got the vac line coming through with my wires a few inches straight down from yours, below C105.