Is there a fuse or something that would blow to knock out the cruise control?
Mine worked fine Saturday for a 150 mile trip but returning home it wouldn't engage.
Any suggestions?.....Thanks Cliff

In addition to fuses, check the adjustment of your clutch and brake switches. These are a common culprit in cruise control woes. Next, check and test all vacuum lines associated with the cruise servo. Finally, check the wiring at the stalk....over the years the wires get flexed back and forth frequently, and they can wear through and break.

The cruise was inop on my 86 when I bought it. I ran some voltage tests, and the servo wasn't getting any power. I traced it back to a broken wire on the stalk. Replaced the stalk and had power to the servo, but it still wouldn't engage. Traced that issue back to the clutch pedal. Adjusted that and all was well and has been fine since.

Let us know what you find.

never2old,

The fuse that controls the cruise control is fuse #14, a 10A (Red). That fuse also powers the radio.

I do get a ghost wipe when make a left hand turn so maybe it is the stalk.
And the radio still works but will check the fuse anyways.
Will let you know...Thanks....Cliff

The wires to the stalk are notorious for breaking due to all the flexing they do over the years. Remove the stalk from the column and you will most likely find the breaks in the wire/wires. It's generally easier to replace the stalk than repair the wires

never2old,

Here is a representative block diagram of a cruise control system:



Key:
1. control unit - usually buried in center console or behind dashboard
2. operating switches - on column switch stalk
3. vacuum pump - under hood, usually next to brake master cylinder
4. servo unit - usually on a bracket over the cam cover
5. brake and clutch switches - half way up the pedal bracketry
6. inductive speed sensor - on the back of the speedometer
7. brake light switch - half way up the pedal bracket

Hopefully this will help you in your troubleshooting efforts.

Cajun

There is a very detailed trouble shooting flowchart in the back of the factory service manual. I used it on my cruise install and found I had two problems: (1) a connector was not seated completely, and (2) the sensor in the vacuum diaphram unit (whatever it is called) was bad. Now I enjoy the benefits of cruise. The 86 manual is online somewhere.
Jim

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Jim

86 SE 355 Body Kit w/3.1 Auto (Sold)
87 T-Top Coupe 2.8/5 Speed new project

I have 3 of these units from different Fieros and all seemed like the diaphram was bad as it couldnt hold vacuum. I took them apart and found that the selenoids have an O-ring that seals them off from the vacuum had all leaked. I RTVed that part and put it back, now it works. It involes taking off the cover(2 screws) and taking out 2 more I think to remove the selonoids, electronics and the Oring is a big oval and it had dried up and cracked.