Simple auto electronics? NOT!

Morich · 05-04-2020, 08:11 AM

I've mentioned a few times about the problems I was having starting my toad, a 2014 Ford Focus. It got into an intermittent problem where it might not crank at times. Back last summer it started acting weird as it might not turn over the first few times I turned the key but I knew a shop would have trouble sorting the question if it was not doing the deed when they were looking so I sat on it and assumed it would get worse. Gradually over months, it got bad enough to think the shop could find the problem and I took it in to Ford. I had done all the simple stuff like assure the battery was good (changed out the old), made sure the cables and connections were good, tight and clean, as this shop had a "diagnostics check" of $140 and I did not want to pay to have them clean the cables!
For added fun, this Fous has a long history of TCM (transmission control module) problems and it now has a lifetime warranty as well as class action lawsuit settlements for any TCM problems.
So the first day they changed the TCM, said to come get it, took it back two days later and they changed the TCM again. No charge due to recall, but the third time they said I needed a new battery which I refused as they had not LOOKED at the battery, tested it, nor even considered they were wrong!
I took it off to another local Ford dealer who had the car for ten days as I refused to pick it up if they did not keep it and try to start it the next day.
Anybody want to guess what they finally found after many tries?

A little help on diagnostics? The car would start fine if you tried it any time up to about 4-5 hours after driving but not if you waited overnight. If you turned the key enough times, it would finally crank and always turned over well and started, just refused to crank. NOT a key, nor switch, problem!

Winterbagoal · 05-04-2020, 08:15 AM

Loose connection at the starter motor? Engine and starter motor casing hot and nuts/bolts expanded and making good contact, starts. Cools overnight or after sitting, and the nuts/bolts cool and contract making the connection dodgy, no start.

Goodspike · 05-04-2020, 08:18 AM

Quote:

Originally Posted by Winterbagoal

Loose connection at the starter motor? Engine and starter motor casing hot and nuts/bolts expanded and making good contact, starts. Cools overnight or after sitting, and the nuts/bolts cool and contract making the connection dodgy, no start.

Or at the main ground connection--basically other end of the circuit.

Winterbagoal · 05-04-2020, 09:38 AM

Quote:

Originally Posted by Goodspike

Or at the main ground connection--basically other end of the circuit.

I based my guess on a similar problem I had with my 1973 Mustang Mach 1 convertible (had all the M1 dressing including the honeycomb grill, but in a ragtop). It had an intermittent no start after use (the opposite) problem which turned out to be the nut/washer at the starter motor casing would loosen after heating up. If it sat overnight, it usually started fine in the morning. I figured it out by accident. While under the hood, I tugged the main cables from the battery and had a friend turn the key, and voila. Just pulling on the battery cable improved the connection enough that it wouuld turn over. Got down underneath, and discovered the loosened nut/washer. Fixed with a locking nut/sprung washer combo.

Morich · 05-04-2020, 11:43 AM

You guys must be part of the outdated old school of repair!
Obvious you are not up to date and using a computer to do your thinking. What the computer does for the real techie tech is let him avoid thinking, so when he plugs it in and it says the TCM is not getting good voltage, he is sure the battery is bad, even if he didn't know it was new and then he didn't bother to look or test as the computer said the voltage was 10.2, totally ignored the fact that the car was starting at the time he got the bad reading!
That's when I went for a second shop, there the test showed the TCM was still bad, so they changed it, said all was good but I had them keep it overnight to be sure. Eight days later, they had changed the TCM, the starter and the relay on the added battery cutoff needed for towing and it still was a problem.
Finally they checked the ground from the engine to the frame!
Lays out like this:
Battery is grounded to frame, TCM is bolted on the engine/transmission but it doesn't work well if the ground from that to the frame is not good and solid!

Old story is that we often get so intent on following voltage that we can forget the whole thing has to be a circuit and that means it has to have a full circle for current to flow.
Bet the techs at the second shop will have this in mind for a while but the first tech has not learned a thing!

Winterbagoal · 05-04-2020, 11:54 AM

Quote:

Originally Posted by Morich

You guys must be part of the outdated old school of repair!
Obvious you are not up to date and using a computer to do your thinking. What the computer does for the real techie tech is let him avoid thinking, so when he plugs it in and it says the TCM is not getting good voltage, he is sure the battery is bad, even if he didn't know it was new and then he didn't bother to look or test as the computer said the voltage was 10.2, totally ignored the fact that the car was starting at the time he got the bad reading!
That's when I went for a second shop, there the test showed the TCM was still bad, so they changed it, said all was good but I had them keep it overnight to be sure. Eight days later, they had changed the TCM, the starter and the relay on the added battery cutoff needed for towing and it still was a problem.
Finally they checked the ground from the engine to the frame!
Lays out like this:
Battery is grounded to frame, TCM is bolted on the engine/transmission but it doesn't work well if the ground from that to the frame is not good and solid!

Old story is that we often get so intent on following voltage that we can forget the whole thing has to be a circuit and that means it has to have a full circle for current to flow.
Bet the techs at the second shop will have this in mind for a while but the first tech has not learned a thing!

For me, at least, it's just a case of "been there, done that".

Fletcher0077 · 05-13-2020, 12:22 AM

Back in the day I bought a 1992 4 WD p/u with manual hubs and 10,000 miles on it.
With hubs engaged and transfer case in 2 WD a vibration like a U joint going out would start at ~ 40 MPH. No vibration with hubs disengaged. I thought what the heck it's still under warranty. I can get it fixed.
The first dealer replaced drive line and U joints and then had the drive line balanced. The second dealer replaced the hubs, bearings, rotors and shocks. The third dealer handed it off to a farm boy turned mechanic.
He put the pick up up in the air, started it and put the transfer case in 4 WD then watched the front end drive train turning. He replaced the yoke coming out of the front differential and problem fixed. The original yoke had been built, lathed slightly off center. The wobble was slightly noticeable when you watched it. Smartest mechanic, didn't use the book but used logical thinking.
But hey....my Ford got a lot of new parts

Morich · 05-13-2020, 08:17 AM

Sometimes it gets to be a bit of a headshaker when we deal with folks who are supposed to know!
Since they were so good at staying with the problem and finally fixing it, I thought I would give them a bit of easy work with a vehicle inspection and the windshield fluid leaking.
Easy to explain that the fluid was a slow leak and took maybe 5-6 days to run dry and I never found fluid under the car. It has the new car feature of being too compact to see the container but I was aware that it requires major body removal to get to it, so it is out of my comfort zone. We discussed it was likely to be a bit expensive but I wanted to do it.
They called in six hours and said the car was ready! They put the car on a rack and watched for fluid, saw none and decided it had fixed itself!
Part of the downside to being in a growing area is that it is really hard to get good service! Still leaks. Just not sure where? Maybe I should take it to a good garage?

Goodspike · 05-13-2020, 08:58 AM

Not every mechanic is a good problem solver, and problem solving involves ruling out the basic cheap fixes that can cause problems.

Then there's the problem of the dishonest mechanic. My SIL was having problems with his older Explorer and took it to a neighborhood mechanic who wrote up a bid for almost $3,000 of work. Reviewing it I knew that none of the work would help because it was an obvious drivetrain issue, not a suspension or brake issue, so we took it to my mechanic. It was a $150 sensor that required another $150 of diagnosis and install time. I suspect that first mechanic would have probably put in that $150 part for free without mentioning it, which he probably pays less than $100 for.