Audiovox CCS-100 cruise control replacement (can't do FE tests)

[MetroMPG]

I won't do fuel economy testing without cruise control... and my aftermarket unit (Audiovox CCS-100) has quit working.

It's actually been out of service for a while. But I haven't been eager to do any speed controlled tests until recently, so I haven't looked into it until tonight.

I verified the wiring is all still good, and the red LED on the servo unit comes on when the set/resume buttons or brake pedal is pressed (as described in the first paragraph of the ROAD TESTING section on page 10 of the manual here: http://www.gadgetjq.com/av_manual.pdf ).

But it simply won't engage.

I also double checked that the vacuum line to the unit isn't kinked (it's not).

Any suggestions on what I should look at?

[wagonman76]

Maybe check and see if the diaphragm in the unit is holding vacuum? Remove the vacuum line. With the engine off, try moving the throttle by hand to move the diaphragm in the cruise unit, then put your finger over the vacuum port and let go of the throttle and see if it holds or not.

I hope you can get it working again. But if you end up ditching it, could I have the control pod for a small sum plus shipping? Ive been wanting one for a long time for the Celebrity as a nice looking replacement for the troublesome stock cruise stick but Audiovox wont sell me one by itself. Itd match my dash perfectly.

[Gregte]

I have an after market cruise control that quit working and it turned out that it had a transistor burned out that activates one of the vacuum motors. I replaced that transistor and it is still working ten years later.

What I had to do to trouble shoot the device was to put it on the bench and devise a speed pulse signal, similar to the one produced by the car, with a signal generator. This allowed me to activate the unit and then examine what functioned and what did not. As soon as I could see that the throttle ON vacuum motor received no electrical signal to its terminals it was fairly easy to trace the circuit to find the burnt out transistor.

If you are not able to do a bench test of the unit, another worthwhile thing I have found to do, regarding malfunctioning electronics, is to visually examine the circuit board very carefully, and with a magnifying glass. Way more often than you would guess the culprit will turn out to be a cracked solder joint. This recently turned out to be the case with the windshield wiper control module of my GMC. It had 5 cracked solder joints on the plug connector. If you take the vehicle to a dealer to get the module repaired (very common problem on this model GMC) it costs about $240 as they just replace the module. Or you can discover the cracked solder and repair it yourself for $0.

I have found cracked solder joints to be the cause of the malfunction on a lot of electronic devices, from computers to radio receivers and various other electronic gadgets. Very few people even think to consider this. Most stuff just gets tossed away and replaced, of course at a much greater expense.

Good luck to you however you decide to resolve it.

[MetroMPG]

Wagonman - if I end up ditching it, the dash control is yours.

Gregte - thanks for the encouragement. I just got off the phone with tech support and they had me do a couple of things (I'm posting this just in case someone else finds this via Google):

1) ensure the unit's LED is blinking with it switched on and the engine running (if you're using the ignition method for input (vs. VSS or magnet kit).

That checked out OK.

2) disconnect and ground the purple wire from the brake switch to ensure it's not the culprit (the LED on the cruise control unit will light when the ground circuit is open)

That checked out OK.

3) ensure the engine is producing enough vacuum (14-20 inches of mercury required for the unit to function). My ScanGauge MAP values showed the car is producing enough vacuum under load. (1 inch of mercury = 0.49109778 pounds per square inch, thanks, Google)

Checked out OK.

At this point, the tech said I'd have to send the unit in. I'll open it up anyway and see what I can see. I don't have a signal generator to do any testing (hmmm, I do have the car...), but I'll at least visually inspect it.

[MetroMPG]

Well, I took apart the cruise control today and learned a little about how it works. Cut to the chase: I need to send it in for repair, or get a new circuit board.

There are three solenoid/check valves to the unit's vacuum chamber which contains the diaphragm / throttle cable.

The first thing I did was ensure the diaphragm & chamber seals are good, connected directly to engine vacuum.

Next I verified all 3 solenoids work when energized directly with 12v.

One labelled "vac" is normally closed and sits between the vacuum line and the chamber. When energized, it permits vacuum to the diaphragm/cable. The other two are normally open release valves, one labelled "vent" (fine throttle control), and the other "dump" (brake press, probably).

With the engine on & the unit engaged, the board is properly energizing (closing) the vent & dump valves, ensuring the reservoir is sealed. But when I press the "set" button, the vac solenoid only energizes weakly, on & off randomly, and doesn't permit enough vacuum through to the reservoir/diaphragm. The DMM shows only low voltage (less than 2v) on the vac solenoid, where the dump/vent solenoids are energized at 8v+.

The circuit board looks OK, but there's obviously something wrong with it. I guess the next step is to call Audiovox and find out if they can fix it, or send me a new circuit board.

[dcb]

Well, you *could* touch all the solder joints with your iron (got that idea from awillard) and see what happens. Then take resistance readings in circuit on all the resistors and make sure the resistors are at MOST their indicated value.

[Gregte]

I have an aftermarket CC that sounds similar to yours regarding the solenoid controlled vacuum valves. It also had 3 of them configured how you have surmised, i.e. one is used for a 'dump' when brakes are applied while one is used for the normal realease of vacuum as required.

Anyway, to make the CC keep the vehicle closer to the set speed I connected the two solenoids together in parallel that release vaccum. This way they both dump when the brakes are applied and they also both release vacuum as required for normal speed control. This has the affect of releasing the gas pedal more aggressively when you top a hill and the throttle needs releasing, thus keeping the speed closer to the actual desired, set speed.

The same could be accomplished by drilling out the tiny hole in the vacuum hose fitting that air must pass through, but electrically paralleling them was more easily reversable than filling in a hole I might drill too large.

[MetroMPG]

Gregte - that's an interesting mod. My unit actually came with two "responsiveness" settings, programmable via dip switches. One seems to be for time delay sensitivity to speed changes, and the other is for the "amplitude" of the response to speed changes.

dcb: I may just do that with the soldering iron. Little project for tomorrow. Plus I'll call Audiovox and find out if they'll just sell the circuit board in case I can't make it go.

[wagonman76]

Since youre not getting 12v to the solenoid, but youre getting something, a cheap fix might be to wire a relay to it. Of course, it might be a temporary fix since whatever is failing is bound to fail the rest of the way eventually.

Another thing to check would be the quality of the wiring to the solenoids unit. Maybe check the resistance of the actual wires? What Ive experienced several times is wires nearly broken inside their insulation. If you test it with a multimeter, it actually shows a good voltage. But put load on it, and it wont pass the current and wont function the device. Ive had this 3 times with my fuel pump relay wiring, and once with the headlights on someone elses Cherokee.

[MetroMPG]

Thanks for the advice. The solenoid plugs directly into the circuit board, which tells me it's got to be one of the upstream components on the board.

I'm going to sheepishly admit that I boxed up the unit this morning to send back to Audiovox for repair. I called them first, but they won't just send me a circuit board.

At this point, it's just a question of available tinker time. I'd rather spend the time finishing up the Kammback than troubleshooting the cruise unit.