Hi,
I've got an 89 240 with a cruise control that occasionally works- most of the time it doesn't. I think I've done the basic diagnostics. I've checked vaccum hoses, I've pulled a vaccum on the hose at the controller in the engine bay and the servo functions. I've checked the wiring and switches at the turn signal switch, brake pedals, etc. Basically everything I can get at.

I don't know how to test the computer and the unit that controls the vaccum. This is the older model that has a reservoir that connects to engine vaccum. IIRC there are 3-4 wires connecting the computer to the vaccum unit. Does anyone know what the voltages should be between these? Is there a way to jumper power to the vaccum unit and test it?
Thanks in advance!
Lyle

Hey, but cruise control or not, at least your wife will drive it! :)

She won't drive it long distances without the cruise. That puts the pressure on to get it fixed.

I have an '85 240 DL with the Dana unit under the dash on the firewall above the passenger's feet. It, too, quit a couple of months ago. Checked vac hoses from the underhood servo to the brake pedal interrupt and from the servo to manifold. Vacuum holds ok. 12 volts at the connector of the module on the inside firewall. What else to check? Puzzling. Dana's are good units. Had an aftermarket unit on an old Chev years ago. Any common fault to check? Any source of a wiring diagram?

Sorry if I just jump in on this. I noticed a box near the ecu above the passengers feet on an 89 I'm parting out at the moment. The ECU on the car had a pink label so I decided to leave it. I noticed as well the what I believe to be another box, maybe the cruise control, has a pink label as well. Does the pink label apply to that box and am I thinking correct with it being part of the cruise control. My 86 with cruise doesn't have that box but the cruise doesn't work either. Maybe I need that box for my cruise, any one confirm this? thanks.

That's the ICU, and no, pink reputation from the ECU doesn't rub off. Ultra reliable, so little value on the parts market.
--
Art Benstein near Baltimore

I wonder if other dogs think poodles are members of a weird religious cult.
-Rita Rudner

On my 89's (YMMV on the 86) the computer for the ignition system is up there somewhere, too, so that is what you may be looking at. The computer for the cruise is over on the driver's side. It's quite a bit smaller, maybe 3x5x1 inches (that's a rough guess from memory).

Wish I could help. Every time I had a cruise problem it was a vacuum leak. I did get into the old Dana boxes, tweaking the range adjustment once, but that has nothing to do with yours. Only thing I can add is yours needs the output from the speedometer board, which may have been disturbed if you've had the cluster out to do any number of other projects, i.e. clock-to-tach, odo gear, lighting, temp comp bypass. I wonder if I retrofitted cruise on my wife's 89, would she then take long trips? (!)
--
Art Benstein near Baltimore

If there are no dogs in Heaven, then when I die I want to go where they went.
-Will Rogers

I've fixed several cruise problems over the years by fixig a vaccum hose. Wish this one was that easy. I've checked the wire to the speedo and it's still attached. I'm thinking about trying to run down used computer and vaccum unit and try swapping parts. My wife doesn't want to drive it on the 60 mile commute to her part-time job so the pressure is one.
Lyle