81 Diplomat Cruise control fuse?

[shadango]

Hey all

When I originally got the car a few years back the cruise worked....used it on the way home from the purchase even. About 38k miles on the car. Yes it is a "survivor" as they say.

But anyways....at some point sometime the cruise stopped working...I don't do a lot of highway miles with it so I haven't been too concerned.

But of course when the tinkering bug takes hold, look out...LOL

I have the service manual.....went through the items. The brake stop switch is way up under the dash and I didn't feel like breaking my back today so figured I would first move on to the easier stuff....

The cable is attached at the carb....I have a speedo so I know the two speedo cables are ok.....I turned the ignition to "on" and worked the cruise switch and can hear the servo clicking as the book says to do....I cleaned up the three wire ends and terminals at the servo anyways, they were a little crusty.

But one "easy" thing left is to check the fuse per the manual. I cant find it.....the fuse block doesnt show that, and everything listed on the block works....and I assume that the fuse is fine since the servo clicks (right?)

But can someone clue me in on which fuse in the block is the one that controls the cruise?

The service manual shows pics for "J-E-T', 'B-F-G', 'X-S', and 'Y" models.

Call me an idjut, but I cant seem to figure out what the 81 Diplomat is.....those dont match the carline codes of J, Y,, M (diplomat), H, P, S and P shown in the front of the manual. So I feel dumb.

So I am going by "F" for F body.....and that image shows cavity #2, a yellow fuse..for rear window heat, speed control and "cornering lamps".....The fuse looks fine to me....I dont have "cornering lamps" and the rear heat connectors are busted at the window...LOL..so no way to test but the fuse looks fine to me...

Plus like I said, the servo clicks when tested.

I am guessing that maybe the stop switch should be my next visit.....in the manual I bought (it didnt come with the car) someone had written the part number and cost for that very switch in the manual on that page. So I know it can be an issue obviously.

But want to rule out the fuse before i contort my aged back into a pretzel and suffer for a week afterwards....LOL

Or maybe I dont need cruise afterall....

 

[Aspen500]

Diplomat would be called "G". The "F" doesn't mean F-body, it's LeBaron. The body letters aren't used for service parts or in the service manual. For example, Aspen is "N", Volare "H", etc.

The power feed to the cruise system should be a black wire going to a 4 pin connector at the base of the steering column. It plugs into one of the blue 3-way accessory feed connectors which is fused by (usually) a 20 amp fuse in the fuse block. It goes to the cruise switch. The servo gets power through one side of the dual brake lamp switch, which gets it's power sent to it through the cruise switch when the system is turned on. That side of the brake pedal switch is normally closed and allowing power to the servo on the dk blue wire. If the servo clicks when turning the system on, the brake pedal switch has to be OK.

Sounds like there's either a problem with the switch in the "set" or "resume" position or the servo is bad, either electrically (holding coil open) or the diaphragm is ruptured. In the speed control section of the service manual, there is the procedure for testing the stalk switches and holding coil. Too much to try and type in here.

 

[shadango]

Diplomat would be called "G". The "F" doesn't mean F-body, it's LeBaron. The body letters aren't used for service parts or in the service manual. For example, Aspen is "N", Volare "H", etc.

The power feed to the cruise system should be a black wire going to a 4 pin connector at the base of the steering column. It plugs into one of the blue 3-way accessory feed connectors which is fused by (usually) a 20 amp fuse in the fuse block. It goes to the cruise switch. The servo gets power through one side of the dual brake lamp switch, which gets it's power sent to it through the cruise switch when the system is turned on. That side of the brake pedal switch is normally closed and allowing power to the servo on the dk blue wire. If the servo clicks when turning the system on, the brake pedal switch has to be OK.

Sounds like there's either a problem with the switch in the "set" or "resume" position or the servo is bad, either electrically (holding coil open) or the diaphragm is ruptured. In the speed control section of the service manual, there is the procedure for testing the stalk switches and holding coil. Too much to try and type in here.

Thanks sir.

Where did you find the info in the factory manual as far as determining what model is what letter?

I did the test in the book for the "locking coil"....momentarily disconnecting and reconnecting the double connector at the servo terminals.....and a click is heard as prescribed....

I figured that since the "click" happens when I use the stalk switch off and on, the switch is ok (as would be the fuse)......?

The holding coil test requires putting the rear on jackstands and running to 35 mph
Leave connectors on at servo
Place test lamp probe on white with red tracer wire terminal of the servo, other probe to ground.
With speed control switch in ON position, depress and release the SET button. The speed should vary around 35mph and the test lamp should remain on until the brake pedal is depressed.

But I guess if the stalk switch is not working right this test wouldnt be valid....

So I guess my next step would be to do the control switch test procedure....

"1-check fuse for continuity"

"2-disconnect 4 wire connector at column"

"3-connect 12v+ to yellow wire in the speed control harness connector"

"4-with slide switch "on" attach one lead of test lamp to the connector (brown wire with red tracer on J,E, T models) other lead to a good ground " (but it doesnt say WHICH connector for "G") test lamp should light and should go off when set button is depressed

"5- move the test lamp lead to the connector dark blue wire, test lamp should light and should go off when slide switch is turned to the off position"

"6- with the slide switch in the on position, move test lamp lead to the connector white wire with red tracer, test lamp should light by either depressing the speed set button or by moving the slide switch to resume.

 

[Aspen500]

If you do the holding coil test and the test lamp doesn't light, then I would suspect the switch or wire between the switch and servo. If it does light with "set" depressed (even if the cruise doesn't work), the switch and wire are OK and then the most probable fault is the servo itself.

Yes, if the servo clicks when turning the switch on, the fuse, wire, stalk switch (on-off part) and brake lamp switch are all functioning correctly.

I found the model designations in a parts catalog. It's also shown in the service manual (page 2 of my '79 manual) in the "Introduction and General Information" section.

It looks like you attach a 12 volt source to the black wire of the 4-pin connector for the switches to the male pin (the component side, to the switch) then a test lamp to the yellow wire. It should light with the SET button pressed. They could have worded that part a little better.

 

[shadango]

I found the model designations in a parts catalog. It's also shown in the service manual (page 2 of my '79 manual) in the "Introduction and General Information" section.

re: the model -- my page two has a "1981 VIn code chart" --- and it shows the Diplomat as an "M" for car line code....but that's all the info there....page 3 talks about the engine and trans serial numbers, the body code plate...4& 5 are code plate interpretation, safety labels and bolt torque reference chart. page 6 is track width, dimensions......and thats it for intro/general info which is where you would think the info would be. The next page starts the lube and maintenance chapter.

No mention whatsoever of the "G" there...but the rest of the manual uses ONLy the J,E,T,X,S,Y,B,F,G codes.....sigh...I guess a misprint? I attached a pic.

It looks like you attach a 12 volt source to the black wire of the 4-pin connector for the switches to the male pin (the component side, to the switch) then a test lamp to the yellow wire. It should light with the SET button pressed. They could have worded that part a little better.

But in step #3 it says the 12 volt test wire connects to the yellow wire???

Wait....so maybe what it is trying to say is "put a test light between the yellow wire in one connector and its mate in the other" ??

 

[GregG48213]

what model is what letter

These letters would make more sense if you had a Chrysler manual prior to 1981. The letter would have been the first digit of the VIN (A.K.A: Carline). 1981 was the first year for the newly expanded VIN to seventeen digits. Evidently it took some time for the rest of the manual to catch up to the new nomenclature. Here's a handy reference:
Diplomat VIN and Tag Decoding

 

[Aspen500]

Any luck with the cruise yet? By luck I mean the good type.