This article is partially RV related. But not the first part. My “work truck” is a 2004 Ford Explorer Sport Trac. It’s a great little truck. I bought it used, with a third party Alarm and Remote Start unit installed. I would be working out in the garage or yard and would hear the locks on the truck “locking”. Anywhere from 3 to 30 seconds apart, all the door locks would click like I was hitting the lock button on the remote. I presumed it was the alarm/remote and started diagnosing around the box. The first anomaly I found was the supply voltage was fluctuating. Odd. I checked the fuses – they were fine. Still had fluctuating voltage. I went to the battery and put my probes on the battery cable clamps – and fluctuating voltage. What? Batteries don’t do that. I put my probes on the battery posts (this battery has the round cylinder posts). No fluctuation except a tiny amount when the locks cycled.
The clamps were tight, clean and no apparent corrosion. So, I took them off and looked inside and I did see a bit of discoloration. Not enough to notice if I wasn’t looking for it. I cleaned it off, put it all back together and no cycling locks. For about three months. Rinse, Repeat – I cleaned them again. Same result. Three months later they were cycling again. This time I cut off the cable clamps and installed new ones. It has been a couple of years now, on the same battery and the problem never returned. The odd thing is I never had a problem starting the engine even with this situation. So there must have been something mixed in with the lead in the clamps that was creating an odd resistive layer that was only resistive at low current but allowed full flow under starting load.
Now, to part two. My son-in-law called with a dead van while they were camping “somewhere out west”. They assured me that nothing had been left on. He took out his meter and we started checking voltage at the battery. He reported that the meter reading was jumping all over the place. Since he has side-flat-post connectors he had to remove the cables to get a direct on the battery reading. The battery was run down but the voltage reading was rock steady. I had him clean the connectors good and after a recharge everything was fine. Since the battery was 5 years old and had been run down, they were also going to replace it a few days later. My thinking is this weird corrosive layer caused a voltage drop to the car. Items in the van (newer van with lots of computers) that are “asleep” drawing very little power wake up as the voltage fluctuates back up. While the van was parked for a couple of days, this cycle was enough to run down an old battery.
So, the takeaway here is it does matter whether you put your meter leads on the cable clamp or the post!
p.s. while I’m here I just have to tell another story about my 2004 Ford Explorer Sport Trac. My previous car was a Saturn Vue. I had rented a trailer from U-Haul using my Vue via their website. Well, I went to the U-Haul website to rent a trailer for my Sport Trac but since I was in a hurry, I didn’t bother to change my vehicle type. I knew my truck was more capable than my Vue, why bother? We got to U-Haul and the service guy came out, took one look and said “I can’t rent you a trailer”. WHY? “Because this is an Explorer”. Wait – its a truck, not an Explorer! “Doesn’t matter, can’t rent you a trailer.”
We left and found a truck at another company (no one else had trailers). But I started researching and sure enough, the U-Haul website confirmed that they won’t rent to anyone with a vehicle with the name Explorer on the vehicle. They insist it is not a safety issue (they will rent to a Mercury-badged version of the same truck). Apparently, they had a spate of liability lawsuits involving “Explorer” named vehicles and the company lawyers won out over reason. As so often they do…….