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Old 05-31-2009, 16:55   #1 (permalink)
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Turn Signals Interfer With Cruise Control

I hope this is not a duplicate post. I can't find the post I tried to make a few minutes ago. I am just learning the forum.

Does anyone have an idea what would cause my cruise control to disengage when I turn on my turn signals? All turn signals and brake lights appear to operate normally. This is on a motor home with a 1992 F-53 Super Duty Chassis. The cruise can be immediately re-engaged by pressing SET and does not happen every time I use a turn signal.

Thanks. Richard
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Old 06-01-2009, 09:51   #2 (permalink)
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Re: Turn Signals Interfer With Cruise Control

There's an intermittent fault in a taillight socket, or its ground wire, causing the cruise module to think you're pressing the brake. Make sure you're using the correct bulb installed the correct direction (note the offset pegs) and check all the frame/body grounds back there.

For the full diagnostic procedure, read this & its caption:

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Old 06-01-2009, 20:50   #3 (permalink)
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Re: Turn Signals Interfer With Cruise Control

Quote:
Originally Posted by Steve83 View Post
There's an intermittent fault in a taillight socket, or its ground wire, causing the cruise module to think you're pressing the brake. Make sure you're using the correct bulb installed the correct direction (note the offset pegs) and check all the frame/body grounds back there.
Steve,

Thanks for the advice and the link to diagnostic procedure.

If I may, I would like to ask a couple of follow-up questions. Since the bulbs for the brake light/turn signals are the same bulbs (undisturbed) that have been in the motor home for many years, I do not think that they are the cause of my problem. However, the intermittent ground fault is a distinct possibility. I did not mention in my original post that I recently also started having a problem with my E4OD transmission not locking up or not staying locked up. I know that it normally unlocks when the brake lights are activated, so there could be a common cause for both problems.

My first question: Is this intermittent ground fault likely to be a short from the turn signal circuit to the brake light circuit or likely to be an open in the turn signal circuit which is back feeding the ground back into the brake light circuit? For some reason I have in the back of my mind that the circuit which grounds the cruise control circuit to disable the cruise or the transmission unlock circuit is in the left turn signal. I took the left lens off, inspected the socket and cleaned the contacts of both the bulb and socket. I did not go any further in looking for a ground fault because I do not know what I am looking for. Any suggestions here? BTW, we tow a car and we always check that the turn signals and brake lights on the MH and car are operating each morning before we get on the road; they "appear" to be working properly. That does not rule out a relatively high resistance short some place.

My second question: The transmission problem started happening as we left Kansas City and seems to correct itself after 15-40 miles of driving, if I stop, shut the engine down, restart and continue on my way. At that point I did not know that the turn signals were also a problem. Since the transmission temperature was running at about 220°F (normal about 180°F) at the torque converter output when unlocked and the engine is running 250-300 rpm faster than normal and the pan temperature was at about 140°F rather than it's normal of about 130°F , I stopped at a Ford garage in Springfield, IL on the Thursday before Memorial Day. They could not even do any diagnostics on it until late Friday and the Service Manager said if my transmission temperature did not get higher I would be alright to continue to our next stop just north of Indianapolis. BTW, we live in Rochester, NY so have another 600 miles to go to get home. Finally my question, will any diagnostic codes which might be stored be in the OBD computer or in a special computer for the transmission? And would a ground fault show up as a code?

Since we live in our motor home for 7-8 months of the year, I would like to have any repair work that might be necessary done in Rochester after we unload the motor home and get back into our home. I can live with the turn signal problem, but do not want to cause either more damage or start causing damage to the transmission. Do you think it is O.K. to drive another 600 miles, especially if the transmission will not go into lockup and runs at the temperatures above. I always drive at 55 mph so I am not pushing it but there must be something in the transmission slipping.

Sorry for the length of the post and thanks for any advice you can offer.

Richard
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Old 06-02-2009, 23:03   #4 (permalink)
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Re: Turn Signals Interfer With Cruise Control

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...the bulbs for the brake light/turn signals are the same bulbs (undisturbed) that have been in the motor home for many years, I do not think that they are the cause of my problem.
That's even more reason to suspect the bulbs. Pull them, clean their terminals & the sockets', and consider replacing them anyway. Then follow their wiring to the ground screw on the body or frame & inspect. A wire that stretches is corroded away inside.
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I recently also started having a problem with my E4OD transmission not locking up or not staying locked up.
Early E4ODs (before '95) are notorious for poor durability, so if yours hasn't been rebuilt since '96, now's the time. It's not cheap, but you'll probably never have another problem from it after the rebuild.
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Is this intermittent ground fault likely to be a short from the turn signal circuit to the brake light circuit...
An intermittent ground is almost the opposite of a 'short' circuit - it's an OPEN circuit (a weak connection; a broken wire; a loose contact).
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...an open in the turn signal circuit which is back feeding the ground back into the brake light circuit?
No, you're not wording that right. An open in the turn signal would prevent the bulb from coming on. And ground doesn't backfeed. It's the GROUND that could be open, causing power from the turn circuit to backfeed into the brake circuit, shutting down the cruise. (MAYBE!)
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...we always check that the turn signals and brake lights on the MH and car are operating each morning before we get on the road...
I'd expect a ground fault to show up then, so your symptom could be unrelated to the brake lights in any way. Go thru that diagnostic procedure & see what result you get.
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That does not rule out a relatively high resistance short some place.
High resistance is the opposite of a 'short' circuit (an open circuit being the highest possible resistance).
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...will any diagnostic codes which might be stored be in the OBD computer or in a special computer for the transmission?
The EEC is the only diagnostic module on your truck, and it monitors the engine & trans. But it flashes the TCIL (on the shifter) for trans faults. Read the 7th post in this thread.
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And would a ground fault show up as a code?
There are codes that indicate circuit faults (including on the ground side), but the EEC doesn't monitor the brake light circuit for them. It only uses the BOO output.
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Do you think it is O.K. to drive another 600 miles, especially if the transmission will not go into lockup and runs at the temperatures above.
Yes. As long as the temp stays under ~190°F, I'd say you could drive around the world. But I'm no slushbox mechanic.
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Old 06-03-2009, 19:31   #5 (permalink)
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Steve,

Thank you so much for such a detailed response to my long post. I am learning so much from you.

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That's even more reason to suspect the bulbs. ..... Then follow their wiring to the ground screw on the body or frame & inspect.
I'll install new bulbs. If it ever stops raining, I will try to trace the ground wires to where they are attached and clean those connections. Do you think just removing the bulbs and test driving would eliminate the feedback into the brake light circuit as a possibility? Obviously, this would be a test only.

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Early E4ODs (before '95) are notorious for poor durability, so if yours hasn't been rebuilt since '96, now's the time.
I'm sorry to hear that! Since my chassis is a '92 and has just under 130K on it, I think you are probably right. I do religiously change the fluid and filter every 15-20K miles. I just hope we can make it back to Rochester for the rebuild. Do you recommend this being done at the only Ford truck service center in Rochester or an independent transmission shop? I know that using Ford will cost me more but they MAY do a better job.

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I'd expect a ground fault to show up then, so your symptom could be unrelated to the brake lights in any way. Go thru that diagnostic procedure & see what result you get.
Obviously, when I take the motor home for service they will run the complete diagnostics. I do not have the equipment (or knowledge) to run the tests.

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....you're not wording that right.
Your right, your restatement is what I was trying to say.

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Originally Posted by Steve83 View Post
I'd expect a ground fault to show up then, so your symptom could be unrelated to the brake lights in any way. Go thru that diagnostic procedure & see what result you get.
I'll have it done.

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The EEC is the only diagnostic module on your truck, and it monitors the engine & trans. But it flashes the TCIL (on the shifter) for trans faults. Read the 7th post in this thread. There are codes that indicate circuit faults (including on the ground side), but the EEC doesn't monitor the brake light circuit for them. It only uses the BOO output.
Thank you very much for that link. I have copied it and will study it to determine whether any of the tests are something I might undertake. BTW, I have never seen the light on my overdrive switch flash when the transmission is not locking up. The only symptoms are a higher engine rpm and an increase in transmission temperature.

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Yes. As long as the temp stays under ~190°F, I'd say you could drive around the world.
I hope your are referring to the pan temperature and not the torque converter output. I installed sensors in both places and the pan temperature has not exceeded about ~140°F, however the T.C. output temps have reached ~220°F. The F-53 seems to have an excellent transmission fluid cooler. As far as driving around the world, I am not so sure about that in light of you recommendation to consider a transmission rebuild sooner than later.

Thanks again for your time and help.

Richard
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Old 06-03-2009, 21:35   #6 (permalink)
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Re: Turn Signals Interfer With Cruise Control

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Do you think just removing the bulbs and test driving would eliminate the feedback into the brake light circuit as a possibility?
Yes, if you can get ALL of them. IDK how your particular motorhome is wired, or how many turn/brake bulbs there are on it. If you can find an original wiring diagram from the body mfr, that would be the most accurate.
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Do you recommend this being done at...
I can't recommend any shop (dealer or independent) in your area. Every shop is different, and only as good as the sum of its techs, managers, & owners. A good tech working in bad shop could fix it, but the suits might rip you off on the price. A good shop with a poor transmission tech would be even worse. And there's no way for me to know - you'll have to do some research locally. Call a few used-car lots & ask where they send their Ford truck transmission jobs. Even the dealership might send theirs out if they don't have a good tech on-staff.
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Obviously, when I take the motor home for service they will run the complete diagnostics.
No, it's FAR from obvious. Even the dealership techs miss stuff like that, or don't know about that publication & end up spending MUCH more time to get the same results. If you want someone to do that diagnosis, either show them that page on their computer, or print it out yourself & bring it to them. But there's no telling what they'll charge you.
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I do not have the equipment (or knowledge) to run the tests.
Read thru it again. It only takes a test light & a cheapo DMM. If it wasn't something a novice could do, I wouldn't have suggested it.
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I have never seen the light on my overdrive switch flash when the transmission is not locking up.
That's not what I meant. The TCIL flashes for DTCs related to the trans. The TC being unlocked isn't a fault - it's a normal operating condition.
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I hope your are referring to the pan temperature and not the torque converter output.
I was guessing based on your number & the normal engine coolant temp. As I said: I'm not a trans guy - I really don't know at what temp ATF begins to break down, but I'm sure you could Google it pretty quickly.
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