Cruise control not working

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Topic author
PaulD
Posts: 48
Joined: Sat Jul 15, 2017 11:12 am
Location: Arkansas

Cruise control not working

Post by PaulD »

Tackling gremlins one by one in my 89 GW. My cruise control will not work at all. After looking a service manual and seeing suggestions from other forum threads, I have run out of things to check. The TSM says to use a special tester to check out the electronics. I do not have that tester but there are several items that can cause this problem and be tested without the special tester. So far I have
- Verified that the brake light switch works OK. When bad, it can prevent cruise from working
- Verified that the 4 amp inline fuse is OK. If bad (open) it can prevent cruise from working
- Installed new multi-function lever on steering column. I did this to fix a wiper problem but it should also eliminate the cruise controls on the lever from being the problem.
- Verified good vacuum. Tested vacuum motor next to engine and it held a vacuum. Also verified that it was getting a good vacuum from engine.

Narrows the problem down to three potential items
1) Vacuum servo on fender next to engine - connects to throttle linkage on carb. I checked vacuum and that is OK but no way to test it electrically. My 88 GW parts vehicle does not have one to steal.
2) Speed sensor in speedometer cable - don't know of any way to test
3) Cruise control module - yellow box under dash on passenger side. I swapped it with one (unknown condition) from my 88 GW parts vehicle but that did not help. No way to test without special OEM tester

Everything points to one of these three items but I don't have any way to verify which one may be bad. I am also leery of buying something used without knowing it is good. Anyone know of any test I can perform that I have missed?

Topic author
PaulD
Posts: 48
Joined: Sat Jul 15, 2017 11:12 am
Location: Arkansas

Re: Cruise control not working

Post by PaulD »

Finally found my problem. Took a lot of testing with my meter but I finally discovered that my control module was not receiving any 12VDC power. Tracked down the problem to the connection at the fuse panel. The power wire connection to the fuse panel had a plastic clip on it that was intended to hold the wire in place on the panel. For some reason, it would not allow the wire to insert correctly and mate with the panel. I removed the clip and inserted the bare spade tab into its proper slot and I had power to the control module. Took for a test drive and cruise control worked.
There is a formal tester (AM P-C-1R) that can be used to test the cruise control system but I did not have one. It plugs into the 14 pin wire harness that connects to the cruise control module. Instructions are in the service manual. As I looked at the manual, it occurred to me that I could use my meter to test many of the same test via the 14 pin connector. That is how I discovered that pin 7 did not have the 12VDC power that is should have.
As a result of my testing, I determined that a lot of easy testing can be done via that 14 pin connector as long as you have the manual to determine what the pin reading (ohms, VDC or VAC) should be. Yes.....there are VAC involved. I will try to consolidate my info and post something here to help others trouble shoot your cruise control system
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tgreese
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Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Cruise control not working

Post by tgreese »

That would be a good deed. None of my Jeeps have cruise, but I'm sure there would be interest from those that do.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
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Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
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candymancan
Posts: 3652
Joined: Tue Mar 22, 2016 11:32 pm

Re: Cruise control not working

Post by candymancan »

i wish my cruise was working. ive tried three boxes.. thr glass fuse behind intrument cluster.. a new servo in engine bay.. new switch on steering column.

still doesnt freakin work
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)

Topic author
PaulD
Posts: 48
Joined: Sat Jul 15, 2017 11:12 am
Location: Arkansas

Re: Cruise control not working

Post by PaulD »

candymancan wrote:i wish my cruise was working. ive tried three boxes.. thr glass fuse behind intrument cluster.. a new servo in engine bay.. new switch on steering column.

still doesnt freakin work
Just for kicks, check to see if you have 12V on pin 7 of the 14 pin connector to the control module in the yellow box. That was my problem. Turned out to be a poor connection to the fuse box. Once I had power restored, I had cruise.
I have prepared a draft write-up on some testing that can be done with a simple meter. It was done using just the wiring diagram. Now that I have my system running, I need to go back and see if I can add any more test point. Hopefully can post something tomorrow.

Topic author
PaulD
Posts: 48
Joined: Sat Jul 15, 2017 11:12 am
Location: Arkansas

Re: Cruise control not working

Post by PaulD »

In response to my problems and the lack of a formal tester, I prepared a tutorial on how to trouble shoot with a simple meter. See the tutorial at
http://www.fsjnetwork.com/forum/viewtop ... 10&t=13029
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candymancan
Posts: 3652
Joined: Tue Mar 22, 2016 11:32 pm

Re: Cruise control not working

Post by candymancan »

PaulD wrote:
candymancan wrote:i wish my cruise was working. ive tried three boxes.. thr glass fuse behind intrument cluster.. a new servo in engine bay.. new switch on steering column.

still doesnt freakin work
Just for kicks, check to see if you have 12V on pin 7 of the 14 pin connector to the control module in the yellow box. That was my problem. Turned out to be a poor connection to the fuse box. Once I had power restored, I had cruise.
I have prepared a draft write-up on some testing that can be done with a simple meter. It was done using just the wiring diagram. Now that I have my system running, I need to go back and see if I can add any more test point. Hopefully can post something tomorrow.

I do remember checking voltages on the connector pretty sure i had power.. and i could see the power changes when i flip the switch on the steering column off and on. I'll check again though.

Forgot to mention my speed sensor works as well, already tried another one and i tested mine anyway the sensor on the fender going down
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)
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