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80 Cruise just stopped working any (sensible) ideas?

Chris

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I used Cruise Control (CC) earlier in the week. And it worked fine. Press end of stalk, CRUISE illuminates on the dash, flick stalk downwards and cruise engages. Took a run up to Laughton Cruiser Centre today, flicked stalk down - nothing. Tried several times, nada. Engine on and off, tried again, nope. Checked handbook for fuses. There doesn't seem to be a fuse actually designated for the cruise that I can see which is odd. Everything else does seem to be fine, hazards, lights, wipers etc etc. Can't find anything NOT working. Checked all fuses anyway and they're fine too. I have tried tapping the motor under the bonnet in good old fashioned style and that hasn't worked.

I have looked at the wiring diagrams in the FSM and it seem a relatively simple circuit. Couple of thoughts as to why it might not work. Cruise cancels if you touch the brakes, so if there was a fault in that switch then maybe it wouldn't set in the first place? Motor gone. It's always possible but as we know these things on Toyotas are incredibly reliable. Perhaps there is a fuse linked to Cruise and I am simply missing it. Break in a wire somewhere. Faulty stalk. After that I am struggling a bit. I could well have upset something with other work that I have been doing, but I don't think fitting the alarm will have touched any of those circuits, plus it worked earlier in the week.

Any experience of this one?

Thanks chaps.

Actually just found a whole trouble shooting section in the supplement guides. If the problem isn't covered by that lot I shall be surprised. I don't understand half of it but will give it a shot.

C
 
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you had your foot gently resting on the clutch pedal.................yes you did.

Frank
 
Wish that was it Frank. I have done some of the diagnostics and it all checks out so far. But gone dark an d hissing down now. So that's that.
 
Could the brake switch be faulty (on)?

edit:

Sorry, you already mentioned that :oops:
 
That is one of the possibilities CP. The brake lights seem to work fine though. One of the test routines (that I have not done yet) actually checks that. I have been a bit surprised at the amount of diagnostics that are available for the cruise system. I printed it out and it's 20 pages. It's the usual 'count the flashing lights' stuff and read off the fault. But it also tells you which bits are working normally too. I am sure it will be something quite simple.
 
I remember someone saying, and no idea what/why/when/if-true that some systems will stop activating if both brake lights are fused / not working.
It was many moons ago and don't know if there is any truth in it. Technically, it could be but not sure if they really are :|
 
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Cripin, on an auto you can not put it into drive if you have a brake light out.
 
CP. Interesting development - in a way coming from your reply. I could only test for one brake light earlier as the current wife was out and leaning out with foot on the brake could only see one lens. Couldn't be bothered to back up to the garage door. So just now after you thoughts, I hammed a sledgehammer (yes I know) on the pedal and went around the back. Both lights working fine. But. Also the tailgate number plate lights were half illuminated. Only when pedal depressed and that was with no key in the ignition. So clearly some current is 'bleeding' through somewhere. Now what this means exactly I don't know. But it shows that something IS wrong. In the current build, I have wired in the new number plate light on the tyre carrier arm. I plundered the towing electrics for power today as a short cut. First job is to disconnect those, then look at the brake lights and then go for a drive. It may be enough of a short or whatever to fool the ECU into saying - don't set the CC. All the way there and back today I had the side lights on. So perhaps some of that bleed was in the opposite direction back into the braking circuit. My dear boy you might have cracked it.
 
Check the bulbs also Chris, if twin filament ones they can sometimes touch and cause what you've just described.
Seen loads before where when you brake the side lights come on.
 
Cripin, on an auto you can not put it into drive if you have a brake light out.


Is this just toyota related?

I picked up my mums ML270 auto after it was parked up from a night out. it started and ran fine. when i got home my dad said it had a brake light out. so do mercs have something else?
 
Gary, they're all LEDs. And as we know, they can behave oddly at times. The new number plate lights were not on at all - just the ones on the tailgate. So I will have to fathom that one tomorrow. But there is a good chance we are at the root here.
 
Seriously? I need to go out and get some spare bulbs just in case! (oops, forgot to quote the bit about the brake lights out and can't put it in drive)
 
Wouldn't bother checking for filaments touching then lol.
Sounds like it's narrowed down to the lighting circuit, should save a load of hassle. Tow elecs could be worth a look over too, since it's started after using them for a supply.
 
CP. Interesting development - in a way coming from your reply. I could only test for one brake light earlier as the current wife was out and leaning out with foot on the brake could only see one lens. Couldn't be bothered to back up to the garage door. So just now after you thoughts, I hammed a sledgehammer (yes I know) on the pedal and went around the back. Both lights working fine. But. Also the tailgate number plate lights were half illuminated. Only when pedal depressed and that was with no key in the ignition. So clearly some current is 'bleeding' through somewhere. Now what this means exactly I don't know. But it shows that something IS wrong. In the current build, I have wired in the new number plate light on the tyre carrier arm. I plundered the towing electrics for power today as a short cut. First job is to disconnect those, then look at the brake lights and then go for a drive. It may be enough of a short or whatever to fool the ECU into saying - don't set the CC. All the way there and back today I had the side lights on. So perhaps some of that bleed was in the opposite direction back into the braking circuit. My dear boy you might have cracked it.

It's only taken my 4 years to contribute something useful....:dance:
 
My favourite line on this entire forum :) :) :) Go Crispin!! Let's hope you're right :p
Hope you get it sorted asap Chris..
It's only taken my 4 years to contribute something useful....:dance:
 
Have you checked both circuits of the stop light switch? Probably the actuator interrupt side of the switch has worn out. Your number plate light strangeness sounds like a bad earth at a common earthing point.
 
Jon, I haven't yet. No. I managed the first couple of tests in the manual before light and bad weather beat me. I am back to work this week so dark by the time I knock off. Got Friday off so I shall look then. However, also got a shipment of steel landing - finally making a welding bench.

It really has been working perfectly since I got the truck and up until last week hadn't had any problems at all. It feels like more than coincidence that the second I furtle around with the electrics, it packs up. I was making such good progress too.
 
Well I think I can probably rule out there being a problem, physically, with the CC. Went out today after disconnecting the new number plate lights just to be sure, and the cruise works perfectly. Until ..... I switch on the side lights at which point it cancels. I figure there must be something going on probably as JW suggested with an earth somewhere. I am guessing, but somehow current is going from the tail light circuit into the brakes and tripping the cruise. This is new though as I have driven all the way to Scotland in the dead of night on CC. And I am pretty sure I had the lights on.
 
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