Fellas, ya can't tell nothing ohming out a circuit that draws 300 amps! Even a few hundredths of a single ohm is enough to practically cripple an alternator for example.

High amp circuits can ONLY be tested under load using voltage drop test. No disassembly required, quick and easy.

http://www.aa1car.com/library/voltage_drop_testing.htm

"It doesn't take much of an increase in resistance to cause trouble. Let's say a 120 amp alternator operates in a circuit that has a normal resistance of 0.11 ohms. If that resistance were increased to 0.17 ohms because of a bad wiring connection, the alternator's maximum output would be limited to 80 amps. In other words, an increase of only 0.06 ohms (almost nothing!) would reduce the alternator's maximum output by almost a third! Under light load, the drop in charging output might not even be noticeable. But in a high load situation, the alternator wouldn't be able to keep up."

 

a friend owns an alternator/starter rebuilding shop he took over after his father retired.
Pat has been doing starters and alternators for the past 40 years, he started working in the shop when he was 13 years old. i have been dealing with them for the past 45 years.
he took a 170 amp case and custom built it for high output so it would fit in the small case brackets on my truck.

 

OK, so we're talking about testing the cable, not the cable connection where it's grounded to the vehicle by ohming from the battery to the engine block?

 

Here's some tests you can try:
Glow plugs ON (timing is a factor)...

• Read voltage from each positive battery post (not the cable) to the GPR large post closest to the front of the truck (supply post).
• Read the volts from each negative battery post to the engine.

If you see significant voltage at these locations, you have poor connection(s) somewhere.

 

Both cable and connections. Just go from "-" battery terminal to a clean spot on block near cable and you can also check to a clean spot to frame.

 

I tested the batteries while the truck was running and got a reading of 14.6V, 12.8 when it's off. Could it be in the glow plug harness connector at the valve cover? I've heard they can work loose on the inside of the cover. If the connector is loose, could that cause a "weak sounding" start?

It was -23C when this happened this past weekend. it's since warmed up and it started fine this morning.
Is there a way to test the glow plug circuitry to make sure that it's ok? what readings should I be looking for?
Thanks, George

 

In Fahrenheit, that's more than 9 degrees below zero! Unless I'm missing something here, even if your truck were brand new, it certainly wouldn't start with authority at that temperature.

 

That's the thing, it always started strong no matter what the temp was. Here in the Toronto area the last two winters have been brutal, -20C to - 30C reglarly and the truck had no problem starting as long as I had it plugged in. This has been a mild winter, most days above 0C 32f and I've noticed this issue a few times in the last 2 weeks.

I took off the wiring harness at the valve cover on the driver side and found it had oily residue inside, (don't know if it should) and I ohmed out the glow plug terminals. Three of the four pins gave an acceptable reading, the second pin from the front was infinite.

 

If he's a friend, perhaps you can ask and get an honest answer. Are all the parts he's using to do the rebuild coming from China? It doesn't seem like the local rebuilder outs out products that last as long as they used to.

Fixing it right is one thing, but if you're hampered by parts quality, there aren't many options. Perhaps a good rebuild will last as long as a new MIC part?

 

That is a great site. Thanks for the link.....saved.

 

when china parts became more common he stocked up on usa made parts and has 3 trailer loads of assorted parts in stock. plus he still uses local made parts while he can get them. he said once the trailers are empty he should be ready to retire.

 

Our local auto electric guy does both starters and alternators. I like the old fashion full service. You have a problem he solves it in 20 minutes at no charge, and you learn something most of the time. Keeping up on brushes, cleaning up carbon and dirt etc, really does help extend the life of the part. But not every rebuilder is the same. Glad we are blessed with one that cares about people. I have often wondered why he speaks Mandarin so well!

 

I recommend getting a megger and checking the cables for voltage drop since the OP lives in Canada. I had a .1 volt drop in my charging cable coming off the alternator to the starting relay that I was able to see with my voltmeter. This can indicate corrosion inside the cable(s). At the age of these trucks, and the environments some are operating in, corrosion is becoming a major concern. We constantly fought corrosion in the wiring of the aircraft I worked on in the Navy. Caused all kinds of problems, phantom problems and failures.

I replaced my entire charging harness, the solenoid and the starter (went with high RPM gear reduction starter) and have had no problems since. The harness is not hard to replace, and it is still available for around $85 on Rock Auto for my 01.

 

I don't know why but both my Fords (truck and Expedition) seem to need a trickle charger or something on the batteries if I let them sit for more than a couple weeks. Saturn doesn't seem to care.


I also have had some trouble with my batteries in the truck and it seems that having 2 in parallel may cause some issues. In 8 years I have had 3 of them "short out", meaning they won't hold a charge and within a half hour of charging, voltage is down to 10.5 or so. They have all be Interstate batteries, 2 from Auto Zone (their Golds) and one from Costco (it went just over 2 years before dying). When they short out, they pull down the other battery as well which is not good.


I keep a Harbor Freight "smart" trickle charger on them and when they are in good condition, the charger will keep them about 13.2 to 13.5. I check the voltage weekly now to be on the safe side, but the truck sits a lot, sometimes for a month at a time.


I'm not particularly down on Interstate, but I don't seem to have problems with my other vehicles or my trailer batteries, usually getting well over 5 years on them before I usually choose to replace them.

 

Gary, try unplugging the radio next time you leave the truck sit.
i went nuts looking for a parasitic draw in my 2 99 crown vics, 97 grand marquis, 2000 F350, and the 2002 F250.

tried it first with the crown vics, and with radios unplugged they could sit for 2 mounths and start rite up.
after that i now unplug radios when vehicles sit.
and i have no more problems with dead batteries after 2 weeks.