spedy7

This has been a bit annoying now on my 85 SE, whenever I have all the electrics going (radio, blower, wipers, lights like today when it decided to rain) at idle the radio sounds like it quits but is still on. Get going again and all is well. Also noticed the radio had noise in sync with the wipers. I'm wondering if there may be a corroded/loose connection or radio, a faulty alternator regulator, or something else causing it and if anyone else has had a similar problem? Full load also shows less than 12v on the dash, just can't check if it's accurate today since it's raining and I have no garage. Another small issue is cold start idle - around 1300rpm as the high idle kicks down it'll start jumping up and down, warmed up it's steady at 800. I just replaced the TPS since it was causing the same issue all the time and could not get it to sit at B+ on one terminal, as well as replaced a broken vacuum tee. My dad got curious with it too and tore down the BACV, cleaned it out and regasketed it. Thanks in advance!

KansasCityREPU

iTrader: (9)

There is a condenser right at the top trans inspection plate. It's purpose is to eliminate noise from other circuits. It has a bullet connector.

LongDuck

Well, it could be a couple of things. In order of likelihood;
1) Battery is weak - if this is an older battery, it may not be holding a charge very well. Batteries don't last long I the AZ summer heat, so unless it's garaged regularly and a rolled gel-cell (Optima, etc.), expect to replace them about every 2-3yrs.
2) Battery Terminal connections are corroded - this will look like white dust on your battery terminals, usually the (+) side. Clean those up and you might be able to restore a good connection which will help all around with electrical current flow.
3) Grounds - yep, I was bitten by this one recently, so check the body ground at the Driver's side strut tower facing the A/C, and also the one on the Starter. Be sure they're good and tight and clean those up. Look for frayed wiring or corrosion on the exposed copper strand wires.
4) Alternator - they aren't as big as you'd find on modern cars, so they don't really put out a lot of juice for charging the battery. Combined with a weak or old battery, and that could be causing a low voltage all around. A lot of us have installed a separate ground from the (-) battery terminal to the Alternator support bracket to ensure a good connection for charging circuit.

That should get you started. Replacing the battery will likely fix you up, even if it's a charging or grounding problem, as having a known good battery goes a long way, and usually requires you to check the cables, terminal posts and ground connections. Good luck,

chuyler1

iTrader: (1)

This is the best explanation of what the condenser does I have found.
Ignition Condensors by Alan Hale

If it fails or is disconnected, I think the common symptom is RPM based whine from the speakers as the flow of current is rapidly stopped/started in the ignition circuit causing a resonance in electrical current throughout the rest of the system.

The fact he has issues in sync with the wipers leads me to other conclusions like bad ground wires or a bad battery.
1) With car off check battery voltage. Should be around 12.5v, if less than 12v, you need a new battery.
2) With car on but all accessories off check battery voltage. Should be around 13.7v, if less than 13, could be alternator issue.
3) Check ground cable on battery and clean as necessary
4) Check ground cable where it meets fender well, there is a smaller cable from harness connnected here too. Clean it all off, lightly sand fender and ground cable terminal to get a good connection when you reinstall it
5) Check ground cable where it connects to starter bolt, clean as necessary.
6) Pull out fusible links and reinstall, give a few back and forth motions to clean off the contacts

Cool little trinket to add to your next Harbor Freight order for cleaning battery contacts...
https://www.harborfreight.com/batter...ner-94450.html

FührerTüner

iTrader: (5)

I'd agree with the posts above and say grounds.

KansasCityREPU

iTrader: (9)

The factory service manual does say that the noise can be cause by things like the wiper circuit and bad grounds. They say to ensure the screws hols the radio to the radio chassis are tighten. No mention of the condensers.

spedy7

My thought too, had a customer with an older chevy come in a while back and the block to battery ground was loose causing problems. Probably the main issue, but sprayed some contact cleaner in all the engine bay connectors I could get to with no real difference. Does anyone have a reference to other ground points besides the battery ground? Also finally got a new battery, other one was 6 years old (!) and only tested 100 cca low, so that can be ruled out. Alternator B+ has a tiny bit of corrosion, that'll get a new one spliced in with a 70 amp alternator someday. I'm thinking the electrical gremlin is under the dash though - had the air on recirc this morning, started it with the radio on this afternoon and the sound was low, went back to fresh air and sound went back to normal. My uncle did say he had the floor flooded at one point years and years ago, so I wonder if that may just be it.

As for the idle issue, can't really get it to go away. Messed with the tps and idle speed and got it set yesterday after finding the double/dual throttle diaphragm line was plugged with a screw and causing a vacuum leak - I just plugged the hole on the intake for now. Probably a stupid question too, but below 1000 rpm the marks on the tach are 100 each right?