Electrical 90 mustang cruise control advice

[Brad Hanks]

Hello all, looking for some fixes for my mustang cruise control. It will not turn on, nor has it ever worked since the day i bought it.
Things I have checked/ observed: speedometer works, it is a 5.0 5 speed and clutch safety switch appears to work (clutch pedal has to be all the way down to start) both cables are attached to throttle body, new buttons on steering wheel, horn works, all three taillights work and do not stay on, brake lights work, has over 150000 miles on it.
Any help on this would be appreciated.

 

[General karthief]

Check the vacuum lines to the cruze control canister and check for power at the switch. I 'll hit up my manual for some specific things to do.

 

[Brad Hanks]

To the servo right? And not 100% on how to check power to the switches.

 

[jrichker]

Dump the codes, look for codes 27 or 29 which are speed sensor codes.
Check to see if the cigarette lighter works - it shares the same circuit/fuse as the cruse control system.

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

 

[Brad Hanks]

The cigarette lighter does work, I checked all the fuses with a volt meter and they are all good. I’ll try dumping the codes the next I’m working on it. Thanks.

 

[BlakeusMaximus]

Could be your VSS sensor at the trans

 

[Brad Hanks]

Even if my speedometer is still working fine?

 

[jrichker]

Even if my speedometer is still working fine?

The Mustang you have has a mechanical speedometer that does not use the VSS sensor.

 

[BlakeusMaximus]

no VSS sensor?? I replaced mine when my cruise wasn’t working and it fixed my cruise control. Cheap part too.

 

[Blown88GT]

...both cables are attached to throttle body....

Cable broken at servo.

 

[General karthief]

I think what he was say'n was the vss does not drive the speedometer, just for the cruise

 

[Blown88GT]

I think what he was say'n was the vss does not drive the speedometer, just for the cruise

VSS is also used to tells the computer when to turn on the IAC motor to control idle on deceleration and such..without it, on a mass air computer, the car can/will stall coming to a stop sign and between downshifts and situations like that. It can also cause other idle surge problems

Causes a code 29 to show. Research that you'll find more answers, but, yes, you need it if you're using a mass air ford eec iv to control the engine

 

[BlakeusMaximus]

I think what he was say'n was the vss does not drive the speedometer, just for the cruise

Right. Gotcha.

 

[Brad Hanks]

I’ll check all these out, thanks. My dad has a 93 and the cruise works on it, I’ll see if I can borrow his vss sensor to see if that’s the problem.

 

[BlakeusMaximus]

Let us know, my money is on that sensor.

 

[Brad Hanks]

Ok, will do. I know when I first got the car it didn’t work and it didn’t have any codes, I don’t know if that makes any difference.

 

[jrichker]

I’ll check all these out, thanks. My dad has a 93 and the cruise works on it, I’ll see if I can borrow his vss sensor to see if that’s the problem.

Dump the codes and find the problem. The process is clearly detailed with lots of pictures. You risk damaging the speedo cable and the VSS sensor if it isn't removed and installed properly.

 

[Brad Hanks]

The cruise never worked and had no codes for years, I don’t mean any disrespect by saying this, but do you think that will help find the issue?

 

[Brad Hanks]

Fair enough.

 

[BlakeusMaximus]

Try a new VSS sensor