Automotive puzzler for you mechanics out there.

[HiFructosePronSyrup]

I've got a 1983 Ford E250 van, with a newish battery (<1 year)

Yesterday was foggy and I left my lights on, needing a jump start later in the evening.

While driving around recharging my battery, I had this problem. The van started making this horrible obnoxious screeching sound. This occured when I first cranked the engine over, while I accelerated, and while cruising at 20-30 mph. It would disappear while idleing, or while driving at highway speeds.

There were two of these noises, with different pitches. The deeper pitch screech would start after and end before the higher pitch screech noise. They appeared to be coming from different places in the engine compartment.

I've always been under the impression that these noises were symptomatic of worn or damaged belts. You hear them a lot from older cars, particularly on cold mornings.

The question is this- why would this noise occur only after a jump start, and why did they disappear this morning after a normal start up?

[MineralMan]

1. Could be a frozen up alternator or A/C compressor

That would cause the belt to slip and squeal. A loose belt will also do it. You need to cause the noise while stopped, so you can look under the hood and see what's going on.

Or, take it in to a diagnostic place and have them locate the noise.

[krispos42]

2. I would guess the fan belts as well

Perhaps condensation from the fog has made them slippery. I would tighten them up and see if that took care of it.

I would also check the voltage output of your alternator to make sure it's running properly. If it's below 13 volts or above 15, it probably needs to be replaced.

Does your power steering feel heavy?

[SacredCow]

3. Jump starts *can* freak out certain electronics.....

My old Beetle, for instance- it's generally best to not jump start any old air-cooled vw that has the original fuel injection (about 1974 through 1979), as it can corrupt the FI module.

So I'd say it's possible the jump start could have been the cause, but I'd be more inclined to say that it was a coincidence.

[Optical.Catalyst]

4. Your alternator is working double duty to recharge the battery

It is taking a bit more torque to turn the pulley.

PS - get new belts.