|
|
|
Hey guys, been having an issue that's driving me crazy. I have replaced almost everything in the cruise control system, and I can't figure this out.
When I set the speed, it will hold it for a few minutes and then just cancel, and start decelerating.
When this happens, I CAN press and hold the set button and accelerate perfectly fine, indicating no vacuum leaks, I just can't reset the speed. I cant resume the speed, nothing. Only accelerate.
I have checked the whole system for vacuum leaks, it holds it perfectly. I've run the OBD for codes and I get 1-1-1 indicating no problem. I have run the OBD component test, and it returns all the codes it should.
I've pulled the vacuum bellow servo, its good. I have replaced the switch/stalk on the steering wheel. I have pulled the serviced the brake vacuum switch and its sealing perfectly/holding vacuum. the switch is adjusted so that it is closed when the pedal is rested.
All my brake lights work, I don't have a lamp failure indicator on the dash at all.
IDK where else to check. Is it possible the vacuum pump is faulty and is not holding the set vacuum like it should?
|
|
-
|
|
|
Happy New Year,
I don't know the 940, but I have a similar problem with my 90 240. This uses the later 90-93 system used in 240's and may be the same as yours.
My cruise shuts down occasionally in very warm weather, but consistently within a minute or two of running high heat through the windshield vents. Because the control unit sits adjacent to that ductwork, I suspect the problem may be there.
I 've had the CU out a couple of times. The connections are clean, and there are no obvious faults in any of the other components. One of these days I'll try swapping in the functioning unit from my 91, but I'm not driving far these days so it'll probably wait till spring.
Regards, Peter
|
|
-
|
|
|
hmm this is a good point. It hasnt started doing this until the weather got colder and I've been using the heat all the time... Is there a way to troubleshoot the CU without just dumping a new one into it?
|
|
-
|
|
|
Hi Sunapee,
I came across this which may be of interest to you. It discusses loss of the speed signal from the gauge cluster to the cruise on your 900.
https://www.brickboard.com/RWD/volvo/1573308/940/960/980/V90/S90/cruise_control_diag.html
Peter
|
|
-
|
|
|
So connector C2 would be in the engine bay on the drivers side strut tower is what I’m reading? That’s interesting, because recently, I’ve had an issue with another connector on the drivers side strut tower not providing a good connection and causing a rough idle/multiple instances of random no-spark no-start scenarios.
|
|
-
|
|
|
Dear sunapeelakers,
Hope you're well. If you decide to separate the sections of wiring harness Connector C2, I'd suggest warming the connector's housings using a hair-dryer.
Old plastic gets brittle with time. Cold also embrittles. Warming will minimize the risk of damage to that important connector.
Separating the connectors' sections likely is necessary to allow a corrosion-remover to penetrate and so restore good current flow.
The connector's housing temperature should be raised to "hand-warm" i.e., not so hot that it is uncomfortable to touch.
I doubt Volvo supplies the connector housing. Even if the housing is available, moving all of the wires will be tedious indeed.
Hope this helps.
Yours faithfully,
Spook
|
|
-
|
|
|
Dear sunapeelakers,
Hope you're well. Your comment about the malfunction starting when "the weather got colder" indeed suggests an electrical source of the problem. The Cruise Control Module (CCM) - best I recall - is not near the an vent.
And, if heat - rather than cold - were the source of the problem, I'd expect the malfunction to intrude during summer and subside during winter.
Dollars to doughnuts, there's a micro-crack in a solder joint inside the CCM. The joint closes when cold. As power flows, the joint heats-up and widens, which cuts the power.
Re-flow the solder on all contacts inside the CCM. Apply the tip of a low-wattage soldering iron (say, 20 watts) to each contact. When the solder changes color from dull gray to bright silver, any micro-cracks will have closed-up. This should take about a second per joint.
Hope this helps.
Yours faithfully,
Spook
|
|
-
|
|
|
Hi,
If the fault is in the control unit, I would think the most likely culprit would be a cracked solder joint in the PCB that is pulling away when it's heated up. You could try to locate the joint and resolder or failing that, resolder the whole thing.
As far as testing components in there, for me that would be above my pay grade as they say.
Good luck,
Peter
|
|
-
|
|
|
Dear sunapeelakers,
Hope you're well. If you've not done so, check the wiring connectors to the vacuum pump. Corrosion can cause intermittent function. An aerosol corrosion-remover (e.g., Deoxit) will reach all connectors' surfaces.
Has the time interval between speed set and disengagement changed? That is, would the system work normally for 10 minutes and now it only holds speed for five minutes, before disengaging? If so, that suggests worsening corrosion.
You should also check the rubber hoses that connect to the vacuum pump. A small crack could cause a slow loss of vacuum.
I don't recall a post reporting cruise control vacuum pump failure. But no parts last forever. A pump that has served for 27 years may have reached the end of its service life. It is thus possible that the pump's motor no longer works properly.
Thus, replacing the in-service vacuum pump with a "known-good" replacement may be the best way to get to the root of the problem.
Hope this helps.
All the best for 2021!
Yours faithfully,
Spook
|
|
-
|
|
|
Hey spook, yeah I have checked all the vacuum lines and they’re all good. I have checked the wiring and there is no corrosion, although the connector for the pump is junk. I have slid the bullet connectors through it and slid them on the correct ports of the pump and they’re making a good connection. I also put some dielectric grease on them to make sure the connection is good.
This did happen a few times sporadically, now it happens every time and will only stay set for a few seconds. Pretty frustrating since I travel the highway to work everyday.
|
|
-
|
|
|
Dear sunapeelakers,
Hope you're well. As the unwanted cut-off gradually occurs more quickly after activation suggests an electrical problem: a component goes from bad to worse.
Even if the Cruise Control Vacuum Pump's (CCVP) connectors are in good shape, the pump itself may be worn-out.
I don't recall a post reporting such a failure. But, as I noted, a factory-installed CCVP has served for 27 years. If the cruise control has been used heavily, the pump may simply have given all it can give.
If substituting a "known good' CCVP does not restore proper operation, then perhaps the Cruise Control Module (CCM) may be the source of the problem.
Have you a "known good" spare CCM? If so, see if that swap is curative. The CCM's location - under the dashboard on the driver's side, clipped to a panel just forward of the door hinges - makes it hard to inspect the wiring harness connectors. A spray of Deoxit - or a similar corrosion-remover - may suffice.
Before doing either of these, it might also be well to inspect the ground points behind the panel in the footwell, forward of the driver's door. A spray of Deoxit should remove any corrosion.
Hope this helps.
All the best for the New Year!
Yours faithfully,
Spook
|
|
|
|
|
