AC Hum?

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

Had the belts replaced sometime back and now when the AC is on, at certain speeds, I get a resonant hum. It goes away when the AC is turned off? Is this a bad belt? Is the AC going?

Any help or suggetions would be great

Post by **Mayhem_J30** » Mon Sep 02, 2002 5:51 pm

if it was a bad belt i think it would squeel instead of a hum. hey Prof can a pulley go bad on the a/c?

Post by **Professor_Mike** » Mon Sep 02, 2002 5:51 pm

Sounds like the belt adjustment may be off. Try running the motor at the RPM you hear the resonance while you watch the belt for vibration.

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

Put the car up on jacks and pulleded covers etc. The belts were so tight! Bedides the "reputable" mechanic use carquest cheapo belts on the car. I am getting replacement belts and will be doing it myself. I just hope the resonant hum was not the bearings on the ac unit from being over tightened

Also found a hose that was not properly connected.

I should be replacing tonight. Will update later.

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

Replaced belt and it is still there. Noticed a few things

I normally do not run AC but when I do the hum starts at a lower speed. I did notice something today when it was raining. When the wipers cycled, the hum would start when the wipers finished (end of cycle). and go away then again.

Could this hum be the start of the alternator going bad

There is no speed at which it starts. More evident when AC on (load condition) Never during acceleration or decel just at normal cruising.

Just put new tires on but this was evident before. No extra noise heard so I do not think it is the wheel bearings or tranny.

Help, ever since the radio crapped out, I am hearing things because I cannot drown them out

Post by **Professor_Mike** » Mon Sep 02, 2002 5:51 pm

You should pick up a cheap stethescope at the auto parts store to trace the noise. Sometimes the alternator will make noise while charging. Try disconnecting the connector on the alternator(not the one bolted on), if the noise is gone the alternator may be failing.

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

I just swapped out the AC Tensioner pulley and viola the resonant hum is gone. What a relief

I also invested in a timing light and checked the timing. It was at 27 deg so I adjusted it to 15 per spec. The guy who did the timing belt never adjusted! I even asked but he said there was no adjustment! I will never use him again. I am going to DIY as much as I can.

Found a good warranty place for those who cannot afford to plunk down 1500. http://www.warrantygroup.com Its by the monthy or year and is reasonable.

Still having problems posting, is anyone else having the same problem?

Thanks for all the input over the time on this issue!

Post by **Q45tech** » Mon Sep 02, 2002 5:51 pm

"It was at 27 deg so I adjusted it to 15 per spec." ?????

I can't imagine it being 27 Deg BTDC and not knocking severely and acting extremely weird .....are you sure you followed every single step in the proceedure including the rpms at 675., IAC discoed, and coolant temp at 176F.

I have seen them at 18 or 19 but never over 20 or under 12?

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

The RPm were around 675 to 700 the best I could tell. The coolant was warmed.

I was getting a hesitation that even my wife could notice. I adjusted tha MAF and that took care of part of it but It never ran just right after the timing belt change. I asked them if they check the adj and they said it was not adjustable (bs). At around 4k rom it sounded like it was noisier than before that is why I questioned the timing.

I folowwed the instructions in the manual to the letter. I am getting rady to do a good raod test in a few and will post later.

I am sure I did everyting correct but any suggestions would be appreciated. I can take constructive stuff.

I will recheck the timing in a few days to see.

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

I do not see anywhere in the manual to disconnect the IAC. I assume you mean the Idle Aic Control Valve.

I road tested the car and it was worse than before.

I used method b in the maual which goes off the power transistor because I did not have an extension.

Is this one of those "opps!" in the manual? Like the location of the bolt to replace brake pads?

Where is the connector for the IACV and I will disconnect and retry the timing tonight. I know the IACV is on the right rear but not sure what connector. The maual is not so clear on this

Your quick input is always appreciated Q45Tech!

Post by **juiceman** » Mon Sep 02, 2002 5:51 pm

Tried to get an extension but could not find one. Talked to a very experience mechanic and he told me that using the power transistor method you have to devide the degrees by two. This means my original reading of 27 is actually 13.5 degrees

I re-timed the car to a 30 reading which is actually 15 and now the car purrs no hesitation or howl @4000 rpm

I was told the power transistor fires twice to the spark pulg wire of one.

I am not sure of the technicals but it worked.

I still want to find an extension, does anyone have any idea how to obtain?

Did they ever get the posting thing straightened out? I can only respond to post that I generated.

AC Hum?

AC Hum?

Solved the problem

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