Frustrating Cruise Control

[piper109]

Vehicle is 99 D1 SD
My cruise was working great but stopped working one week to the next.
I have worked on them before on older D1's with limited success so I know how fickle they are.

All the electrical signals check out with good voltages and good grounds.
Vacuum hoses etc are all in good condition and by externally using a positive wire and two grounds I can make the pump work and the actuator to pull in and hold so there is nothing wrong there.
I can only assume that the CC control unit has gone bad. I have three in total and I am faced with having three bad ones:banghead:.
I can get no power on pin 1 so for whatever reason the internal relay is not pulling in.

Looking to beg, borrow, buy or steal a "known good" AMR 1173.
Has anyone actually solved this common problem?

Thanks, Steve

 

[d1driver]

Wow Steve. I am in the same boat. Bought a replacement from someone on here and it worked twice, then quit. My vacuum lines are fine as well.

 

[piper109]

Well mine started working again today but I wonder how long for.
It has worked long enough for me to ascertain that there is voltage on pin 1 (power to the vacuum pump) only when you set a speed.
This means there is no point in checking for voltage there until you are going about 30 mph and attempt to set the speed.
If it works intermittently I might just remelt the solder connections on the PC board. This can sometimes heal old electronics where mechanical connections deteriorate.
If Lucas was the "prince of darkness" then surely Hella must be the "Baron von Dunkelheit".

Steve

 

[jymmiejamz]

Have you replaced all of your vacuum lines? If not do that first.

There is a really good diagnostic flow chart in either the 94 or 95 workshop manual, and its only in that one. I have it printed off somewhere, I'll have a look in my box at work and see if I have it still.

 

[piper109]

As I stated in my original post, I have thoroughly checked all my vacuum hoses and electrical signals.
I also have the diagnostic chart you mention and I have used it so often I pretty much have it committed to memory.
All my electrical signals check out correct and everything points to the ECU. It seems they are notoriously flaky.
I have had it working, stop , then next time I use the vehicle it no longer works. Sometimes turning the cruise off at the dash then back on again makes it work again. Yes I have checked the switch, cleaned it yadayada. I think temperature may be affecting some component or another in the ECU or perhaps something is breaking down with age. I have three of them. Hopefully I can get some reliable operation out of one of them.

Steve

 

[d1driver]

I have sucked in on the vacuum lines at the pump and I can collapse and hold the diaphram thing on the intake closed without air leaking. Mine worked fine forever until about a year ago. Even with replacement pump in there, it doesn't work at all now.

 

[Two Cold Soakers]

Just throwing this out there...

Is there a way the Vehicle Speed Sensor could fail, allowing the speedo/odometer to work, but not the CC?

 

[jymmiejamz]

If you've gone through the diagnostic flow chart and it leads to the ECU, then you need an ECU...

 

[1MITCH1]

My cruise was inop and vacuum lines looked fine, all connections tight. New vacuum lines and now it works. Do yourself a favor and put on new lines before you do anything else. $2 worth of hose and 10 minutes isn't too much to ask.

 

[piper109]

But I have new lines already. Yes I will have to replace the ECU even though I have 3.

Problem is sometimes it works, sometimes it doesn't. Yesterday it worked.
I got a full 13 volts going to the pump on pin 1 after I set a speed. Today nada. Yes the pump works fine...when it gets voltage.

I would love to be able to repair the unit. I found a place on Ebay that will repair it for about $65. I think thats my next step.
I was hoping to find someone who had gone further with it than me.

Steve

 

[MilSpec]

But I have new lines already. Yes I will have to replace the ECU even though I have 3.

Problem is sometimes it works, sometimes it doesn't. Yesterday it worked.
I got a full 13 volts going to the pump on pin 1 after I set a speed. Today nada. Yes the pump works fine...when it gets voltage.

I would love to be able to repair the unit. I found a place on Ebay that will repair it for about $65. I think thats my next step.
I was hoping to find someone who had gone further with it than me.

Steve

Sounds like a loose wire or ground somewhere.

 

[Le shed]

Have you checked the brake pedal switch? My 95 RRC was doing a similar thing and it was leaking. Also it is worth resoldering the pcb.

 

[piper109]

Have you checked the brake pedal switch? My 95 RRC was doing a similar thing and it was leaking. Also it is worth resoldering the pcb.

Yes, I have checked both of them. One is on the vacuum switch and it allows voltage to pin 9. It cuts the unit off when brakes are applied. The other operates the brake lights and applies voltage to pin 5 when brakes are applied. Both are working. I get 12 plus volts. How does a switch leak? Do you mean not full voltage?

I have 3 ECU units. I have resoldered the pcb in one but not the one presently in the car, that works intermittently.

Steve

 

[d1driver]

Did you replace the vacuum line that goes through the firewall? If so, where does it go inside?

 

[jymmiejamz]

Did you replace the vacuum line that goes through the firewall? If so, where does it go inside?

It goes to a switch on the brake pedal to sense when you put on the brakes to disengage the cruise control.

Replace the cruise control ECU with a new one, its not surprising that used ones don't work since they go bad so frequently.

 

[piper109]

Did you replace the vacuum line that goes through the firewall? If so, where does it go inside?

Yes I have replaced that line. It goes to a black vacuum switch on the brake pedal. Just remove the cover above the pedals and follow the hose.
Be careful, the vacuum switch is held in place by very small plastic tabs and if you break a tab (easy) the switch will not sit properly and have a vacuum leak when the pedal returns. This will stop the cruise from working.
The vacuum switch also has an electrical switch which connects to pin 9 via the cruise lockout relay. You will probably need to remove the plug for this in order to remove the switch assembly.

Steve

 

[piper109]

It goes to a switch on the brake pedal to sense when you put on the brakes to disengage the cruise control.

Replace the cruise control ECU with a new one, its not surprising that used ones don't work since they go bad so frequently.

Its my understanding that they are no longer available new. They would be very expensive in any case.

Steve

 

[piper109]

Well I sent my cruise ECU off to a place in Moscow Idaho and had it repaired for about $70.
It works now

 

[fishEH]

Well I sent my cruise ECU off to a place in Moscow Idaho and had it repaired for about $70.
It works now

Cool. I bought a used(working) cruise ECU and I hope that fixes mine.
What was the name of the place?

 

[discostew]

Hey piper109, Please tell me more about the company that fixed your cruise module. Its becoming a big problem for us. I havent been able to find any modules and need to find a way around this. I find that whatever drives the vac. pump is taking a shit most times. I get no ground path,but have batt. pos. at the pump. I have 3 modules I could send them right now.