Q I own a 1995 Plymouth Voyager with a 3.0-liter engine. When it gets really hot in the summer, over 90 with high humidity, the starter does not work. There is no power to it. I have to connect jumper cables from the positive terminal on the battery to the bolt on the starter to get the starter to engage.
This has gone on for many years. I have tried everything: new starter, new key assembly, new relays. I have literally replaced everything except the wiring harness. What do you think the problem is? It has something to do with heat, because it never happens unless it is very hot outside, and once the van sits for an hour or so it will work again.
A You were on the right diagnostic track with the jumper cables. Anytime a starter motor will not engage and crank the engine, safely use the jumper cables to bypass the starter's electrical wiring and components, as you did.
But don't overlook the possibility of a poor electrical ground between drivetrain, chassis and battery. Test this by connecting the black/negative cable as an additional ground between drivetrain and negative battery post. Typical culprits include cables and connections, ignition switch, relays and solenoids. Double-check the starter relay and auto shutdown relay and their sockets in the fuse/relay box. Depending on whether your vehicle is equipped with the three- or four-speed automatic transmission, check the park/neutral safety switch. With the four-speed, a scan tool may be able to identify fault codes with the starting system as well.
Chrysler issued service bulletin 08-53-94 that identifies a poor quality positive connection at the battery as a possible cause of intermittent cranking problems on the 3.3-liter V6; it's worth a check.
You could also try hunting for the lost voltage with a series of voltage-drop tests. This is a bit safer than using the jumper cables to crank the engine because all you need to do is work back toward the battery and measure voltage-to-ground at each major starter connection. There shouldn't be more than about a tenth of a volt drop per connection. A larger drop in voltage may indicate high resistance in a cable or connection because of heat.
Q An interesting thing happened with my 2007 BMW 5-Series. I parked and locked the car with all windows shut and the moonroof closed. When I returned two hours later, all four windows were down and the moonroof open. Any clue as to what may have happened?
A Who else has a key? Teenage son, perhaps? All kidding aside, the most likely suspect is the power window control module -- yes, another electrical system now controlled by a microprocessor. Have the dealer use diagnostic software to interrogate the vehicle for "5120 locking system" faults.
