cruise control not working

scottg · Post by **scottg** » 26 Feb 2012, 11:46

I have a '93 850 GLT and the cruise does not work. I have replaced the brake vacuum cut-off switch, the control module, the switch tree and still nothing. I don't even hear the vacuum pump working. I did run some tests and could make the vacuum pump work with jumper wires placed on the posts under the control module, but it doesn't seem to come on when needed. The other tests I've run showed the "-" side of the selector switch was bad, ergo its replacement. The brake cut-off switch I had to replaced because I broke it messing around under the dash. I am pretty sure it is adjusted correctly. The only code I get from the diagnostics is a 1-2-2, no speed detected (or sometihg like that).
Any ideas? When should the vacuum pump come on?

Post by **rspi** » 26 Feb 2012, 12:54

Go for the simple stuff first. Check vacuum lines, mine were worn through under the battery box. Then I had a linkage broke at my gas pedal (from the servo pump).

Post by **Ozark Lee** » 28 Feb 2012, 22:19

Most of the time the hard plastic line from the vacuum pump to the firewall is cracked. Have you installed the jumper wires into the cruise relay sockets to verify that the pump itself is working?

It sounds like you have done all of the DTM-2 tests already.

...Lee

scottg · Post by **scottg** » 01 Mar 2012, 18:41

I have run the jumpers under the control module and the pump starts up jsut fine. I pulled the pump out and inspected the hoses, and all seems fine. When does the vacuum pump start up? When the car runs or when asked to by the cruise?

Post by **erikv11** » 01 Mar 2012, 19:30

Vacuum pump starts up when the cruise is activated, when you actually set a cruising speed.

scottg · Post by **scottg** » 01 Mar 2012, 19:48

Thanks. I NEVER hear the thing running at all and the cruise doesn't even try to engage. I'm getting stumped over this one. New brake cut-off switch, new control unit, new switch tree, still nothing!

Post by **MadeInJapan** » 02 Mar 2012, 16:00

I had the same problem, it was a broken wire right under the switch on the stalk at the steering wheel- it will come apart fairly easily. Look in there- all I did was use a piece of solder and tape and mine worked again.

Post by **rspi** » 02 Mar 2012, 20:22

My linkage between the vacuum servo and the gas pedal was loose.

scottg · Post by **scottg** » 04 Mar 2012, 09:50

I've checked and metered the wiring to the switch and all tested just fine. As I meter the tree switches, all test just fine. The "-" part of the switch tested bad at the point under the control unit which is why I replaced the tree. All fuses are good, but I am nearly convinced it's an electrical problem somewhere, but I don't know where.