Cruise Control Servo clicking in garage? (Page 1/1)
Skybax MAY 30, 09:32 PM
Ok this new phenomenon started today, I just fixed 2 unrelated problems last 24 hours and new one pops up (2 steps forward, one step back, lol).

When I was about to take the 86 GT for test drive, sitting in quiet garage with the ignition key on I hit the brake pedal before cranking and heard a loud click from engine compartment. Upon investigating it is the cruise control servo switch with the red 2-wire connector above the coffee can.

Its never done that before, so at first I thought I might have accidentally bumped the turn signal stalk and turned the cruise control on, but the stalk was off and after reading archives I learned this shouldn't happen anyways under 25 mph, so it shouldn't be clicking in the garage with just the key on when I push the brake pedal.

Everything else seems to be functioning normal including brake lights, so for now I unplugged the red connector at the servo and it doesn't click anymore when I hit the brake pedal.

Any thoughts or direction why its getting a signal when it shouldn't?

PS: This happened after I was bleeding brakes, so I'm wondering if it has anything to do with brake switch, or just coincidence...

[This message has been edited by Skybax (edited 05-30-2021).]

phonedawgz MAY 31, 06:46 PM
Cruise vacuum "vent" solenoid. It "vents" the vacuum when you put your foot on the brake, making sure that the cruise immediately disengages.
fierofool MAY 31, 09:35 PM
I had a similar incident on one of my previous cars. Everything was off and I was working in the engine bay. Suddenly I saw a wisp of smoke come up from the solenoid. It was beginning to melt. Why it had power, I don't know, but I replaced it and the cruise system continued to work properly.
Skybax MAY 31, 10:25 PM

quote
Originally posted by phonedawgz:

Cruise vacuum "vent" solenoid. It "vents" the vacuum when you put your foot on the brake, making sure that the cruise immediately disengages.



Digging in the archives again, I was reading the stuff you wrote here...

https://www.fiero.nl/forum/...120111-2-113146.html

I'm trying to use that to help me start looking in the right area. My understanding is that solenoid/servo with the red 2-wire connector should not be clicking every time I touch the brake sitting in the garage with cruise control turned off. (if I was cruising down the highway with the cruise control on that would be a different story)

So its getting power when it shouldn't and I'm guessing a problem in the turn signal stalk, module under console carpet, or brake switch circuit. Problem is where to start, because I'm not trying to diagnosis a non-working cruise control, I'm trying to understand why that has power when it shouldn't. (potential fire risk or other)

[This message has been edited by Skybax (edited 05-31-2021).]

Skybax JAN 17, 11:33 PM
Decided to revisit this issue, so if I understand this correctly...

- Sitting in the garage with the ignition on and engine off, if I have the cruise control lever turned ON, the vent solenoid with red connector near coffee can should click when I press on the brake pedal (it does)

- Sitting in the garage with the ignition on and engine off, if I have the cruise control lever turned OFF, the vent solenoid with red connector near coffee can should NOT click when I press on the brake pedal (it does)

- That means system thinks cruise control is turned on when lever switch is off, so I disconnected cruise control wire from lever at bottom of steering column, and vent solenoid STILL clicks when I press brake pedal

Considering the cruise control modules rarely go bad in these cars, and with the cruise control lever unplugged, why does the brake switch still act like the lever is connected and turned on? What am I missing?
theogre JAN 18, 11:42 AM
Brake vent solenoid operates independently and Cruise box etc has nothing to do w/ it. Is on Radio fuse, Hot in run or accy.

One part of One switch on the pedal controls it.
Pedal switches wear out, get moved or pedal doesn't return right. Wiring can problems too. Any can cause intermittent connections.
besides plugs at pedal switch and vent solenoid, have several other connects and fuse just for + wire. Splices and plug and bolted ground for - side.
84-87 G400 ground often have rusted and hard to reach because under body and need to unscrew inner fender just to see.

Cruise release vent on many other cars have large Vac Line to the Brake Pedal to do same. Fiero only uses the solenoid because GM didn't want another 9 feet or even longer of vac line. (PB vac line is ~ 9 feet of mix of hard and soft line w/ several joints.)

Big Release plumbing makes Cruise servo to Dump all vacuum instantly.
W/o that the small servo valves add/release vac very slowly and engine can can stay at RPM or even rev faster when you're trying to stop. And that's assumes cruise servo and rest works right.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 01-18-2022).]

Skybax JAN 18, 04:09 PM
I'll check/test both pedal switches this weekend, thanks.
Skybax JAN 21, 05:28 PM
Update (head scratcher)

Here are some pedal switch test observations:

- With the ignition key on and CC lever switch OFF there is 12v on the yellow and black (both sides of the switch) on the brake pedal
- With the ignition key on and CC lever switch ON there is 12v on the yellow and black (both sides of the switch) on the both pedals

- Apply the brake pedal and the test light goes out, so the switch works and engine compartment vent solenoid clicks
- Apply the clutch pedal and the test light goes out, so the switch works and engine compartment vent solenoid does not click

Moving on to the CC module test observations:

- Pin A should have +12v when the stalk switch is on (yes it does!)
(if not check if you have power going into switch, if not you need to check back to the fuse box, if you do then something wrong with switch/wiring)

- Pin G should have +12v (yes it does!)
(if not, check your brake and clutch pedal switches again)

- Pin M should have +12v when you press the 'Resume' button (yes it does!)
(if not, stalk switch or stalk wiring is defective)

- Pin L should have +12v when you press the 'Set' button (NO, it has power at all times!)
(if not, stalk switch or stalk wiring is defective)

Thought I found the problem with Pin L having power all the time, so I plugged in a new CC stalk lever and retested it:

- Pin L should have +12v when you press the 'Set' button (yes it does!)

The new CC stalk lever fixed SET button problem, however original problem still exists... The engine compartment vent solenoid (red connector with purple wire next to juice can) still clicks when I hit the brake pedal with the ignition on when the CC lever switch is OFF, and its my understanding that should ONLY happen when the CC lever switch is ON. I still don't understand why the vent solenoid is getting power/clicking with CC lever switch OFF, what am I missing? Its driving me insane!

[This message has been edited by Skybax (edited 01-21-2022).]

theogre JAN 23, 01:32 AM

quote
Originally posted by Skybax:
The new CC stalk lever fixed SET button problem, however original problem still exists... The engine compartment vent solenoid (red connector with purple wire next to juice can) still clicks when I hit the brake pedal with the ignition on when the CC lever switch is OFF, and its my understanding that should ONLY happen when the CC lever switch is ON. I still don't understand why the vent solenoid is getting power/clicking with CC lever switch OFF, what am I missing? Its driving me insane!

No!

Again, Brake Solenoid Vent Valve As Nothing To Do With CC Switch or the Module.
Valve Will Open with Key in ACCY or Run then hit the pedal.

Many to Most FWD and other Front engine cars w/ vacuum CC have Vac Line to the pedal switch that mechanically vent the servo. In those, the thing is often 1/2 switch and 1/2 valve in the pedal assem. example: lookup STANDARD MOTOR PRODUCTS SLS234 and related at RA etc.

Brake Venting Kills CC even when module or servo are bad and try to keep servo "active" when you're stopping the car. I think this is to meet FMVSS and related rules in other countries for vacuum operated CC. (I'm not digging thru FMVSS to check.)

ETA---> I believe CC systems are under FMVSS 571.124 regulates all throttle controls. This section of regs doesn't have testing etc like brake and lighting sections so hard to say here. (Finally made a site to format rules/laws so much easier to read them...)

[This message has been edited by theogre (edited 01-23-2022).]

Skybax JAN 23, 12:53 PM

quote
Originally posted by theogre:
Many to Most FWD and other Front engine cars w/ vacuum CC have Vac Line to the pedal switch that mechanically vent the servo. In those, the thing is often 1/2 switch and 1/2 valve in the pedal assem.



I'm with you there...


quote
Originally posted by theogre:
Brake Solenoid Vent Valve As Nothing To Do With CC Switch or the Module.

Valve Will Open with Key in ACCY or Run then hit the pedal.



Therein lies the confusion... You are saying that when these cars rolled off the assembly line, the vent solenoid "clicked" when you hit the brake pedal with the ignition on, regardless if the engine was running, and regardless if the CC lever switch was ON -or- OFF, so I've been trying to fix a normal sound/symptom.

I was 99% certain that my previously owned like-new GT's did not "click" when I hit the brake pedal with CC lever switch OFF.

Also, when I read through the archives, most of the CC discussions mention the "click" only when the CC lever switch is ON.

I'm not saying you are wrong, I'm just saying it contradicts what I read in the archives and what I experienced previously, hence the confusion. I will look at the wiring diagram to try and understand it better, but its not one of my strong areas, thanks.

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PS: With NOS stalk installed, everything hooked up, ignition on, everything tests normal... and the solenoid "clicks" when the CC lever switch is switched from the OFF position to the ON position, which is what the archive discussions were probably referring to (and it clicks when brake pedal is applied regardless if the switch is on or off). So it seems everything is working correctly, I just don't remember my other 2 GT's clicking all the time when brake pedal is applied, weird. Maybe another member with a stock GT and working CC can post if their vent solenoid clicks when they hit the brake pedal with ignition on and CC switch off.

[This message has been edited by Skybax (edited 01-23-2022).]