vbatla

Many years ago the cruise worked perfectly. The first indication of malfunction was its inability to hold speed. Then finally nothing. I performed all of the diagnostics in the WSM. All passed. I also soldiered the circuit board in the control unit. I can hear a click from the Control Unit when I try to engage or disengage the cruise. With the ignition switch on (motor not running), bridging terminals 3 & 5 and 7 & 12 (of the connector that plugs into the control unit) engages the actuating cable. With the engine running should that same bridging sequence cause the actuating cable to move as well? Resulting the engine to speed up? Thanks

Ed MD

Check your vacuum lines. There's a "one way valve"at the booster, its blue and more likely its leaking.

6mil928

Do all 928's have cruise? My cruise is also not working. I ordered a used 3 way from 928 int and it looks different than my 3 way. Any ideas?

vbatla

Not sure if all 928s have cruise. The 3-way cruise control lever on mine is just under the wiper control. Not sure about the 81's. I tested the vacuum and it's very strong. I'm going to try another control unit. There's a guy selling them on eBay for 150.00, guaranteed to work. We'll see what happens.

Vilhuer

Early S4 were available without cruise up to '87 MY at least in some ROW markets.

6mil928

I thought the S4 started in 87?

Vilhuer

Yes, I meant '87 S4 was available without cruise for sure and '88 S4 might be first model year when it was installed to every 928.

6mil928

Ok

vbatla

Put the eBay control unit in today. That fixed the problem! Also, I disconnected the vacuum line that goes through the firewall. There's a leak under the console that will be addressed when the dash comes out. The speed hardly varies now due to much more consistent vacuum.