bad alternator causing Engine overheat code?
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Senior User
Joined: May 2005
Posts: 128
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From: NEWTOWN, ct
bad alternator causing Engine overheat code?
long story short.
180k on my 1999 f250. needed all new plugs, exhaust manifolds, coils, and a bunch of other ****.
if plugs were stuck and since the bolts for the exhaust manifolds were stuck in the head, it would have been clos to 3 grand to do the work on an old motor. I went the Jasper route and repowered the truck.
Since I got it back it has run great, but occcasionally, it gets a cylinder head temp code that send the temp gauge instantly hot, and eventually goes into "limp" mode. yet when plugged into the OBD scanner the temperature always reads an appropriate temp for the conditions, even when the temp needle is pinned (still only reading around 230 degrees on the highway) as soon as I turn the key on and off, it goes back to normal. First my guy thought it may be a bad coil, even though I purchased all new motorcraft coils from ford and brought them to him myself to save money. Then he said Jasper suspected a bad PCM. My guy recommended it go to ford for a diagnosis, and if it was a jasper, issue, it would be figured out under warranty.
Ford almost immediately said No way to the PCM issue and said it was exactly what the code said, a bad cylinder head temp sensor (which is new in the jasper block.)
So I bring it back to my guy who performs the head temp sensor swap under warranty and put about 75 miles on the truck without a hitch. I was psyched. After 3 days of driving it does it again. My mechanic had one of his guys look at it again today and he's 100% certian it's the alternator seding out bad voltage to the PCM and shooting a code. he's going to replace it free of labor and charge me his cost for the alternator.
I should have came here right off the bat, but here I am now, I cant ever tow with this because it cant be going into limp mode while towing a backhoe up a hill!
Please tell me someone has experience with this issue!!!
180k on my 1999 f250. needed all new plugs, exhaust manifolds, coils, and a bunch of other ****.
if plugs were stuck and since the bolts for the exhaust manifolds were stuck in the head, it would have been clos to 3 grand to do the work on an old motor. I went the Jasper route and repowered the truck.
Since I got it back it has run great, but occcasionally, it gets a cylinder head temp code that send the temp gauge instantly hot, and eventually goes into "limp" mode. yet when plugged into the OBD scanner the temperature always reads an appropriate temp for the conditions, even when the temp needle is pinned (still only reading around 230 degrees on the highway) as soon as I turn the key on and off, it goes back to normal. First my guy thought it may be a bad coil, even though I purchased all new motorcraft coils from ford and brought them to him myself to save money. Then he said Jasper suspected a bad PCM. My guy recommended it go to ford for a diagnosis, and if it was a jasper, issue, it would be figured out under warranty.
Ford almost immediately said No way to the PCM issue and said it was exactly what the code said, a bad cylinder head temp sensor (which is new in the jasper block.)
So I bring it back to my guy who performs the head temp sensor swap under warranty and put about 75 miles on the truck without a hitch. I was psyched. After 3 days of driving it does it again. My mechanic had one of his guys look at it again today and he's 100% certian it's the alternator seding out bad voltage to the PCM and shooting a code. he's going to replace it free of labor and charge me his cost for the alternator.
I should have came here right off the bat, but here I am now, I cant ever tow with this because it cant be going into limp mode while towing a backhoe up a hill!
Please tell me someone has experience with this issue!!!
Fleet Mechanic
Joined: Aug 2005
Posts: 1,339
Likes: 5
From: NJ
Well 230 deg is overheating in my book, my 04 5.4 never goes above 195 or so, maybe 200 on a real hot day, what is your normal temp when the gage is not hot? I would be very surprised if it turned out to be the alternator
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niceguyeddie
1999 - 2016 Super Duty
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Apr 29, 2014 07:54 PM
arbryant1
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Apr 4, 2014 02:24 PM
1986, altenator, alternator, bad, car, code, cylinder, e150, engine, expedition, ford, o7, obd, overheat, overheating
