this is totally new to me and i am wondering if anyone has ever had this happen

1. occurs at 28mph and faster but loudest loudest between 28 -38mph
2. sounds like a loud insect buzzing
3. origin of the sound is behind the center area of the dash behind the climate controls perhaps even a bit to the left near the cluster
4. there appears to be no effect on anything related to driving or any system that operates from engine to heating...everything seems to work perfectly despite the insect sound.

after going through pretty much anything that seemed logical within the car because the sound originates 100% sure in the dash area the one thing that eliminated initially the entire sound was pressing the the relays tighter into the electrical panel. the sound was gone after that but has returned as of yesterday but only in the smallest way.......barely noticeable and NOT everytime i drive the car.

does anyone know if any particular relay is susceptible to buzzing when it starts to heat up or fail?

If it's a relay that's buzzing and mostly just under load at higher road speeds, not plastic vibrating, and if I had to bet, it would be a failing fuel pump relay. In 700/900s, it's either the tall white relay, 2nd row left in front of the round red bulb out sensor relay, or in later B230Fs it can be the small cube relay, rightmost in the front row. Drive with your ash tray holder removed and simply touch the top of the ful pump relay when it's making noise. You may well feel it buzzing or the sound might change when being pushed down.

If that's it then later remove it, with minimal wiggle pulling it straight up using neighbouring relays for hand leverage, and carefully inspect under a bright light the relay case, the relay bottom, relay spade contacts, relay tray plastic socket and down into the female contacts for signs of overheat or anything looking less than pristeen. If it's the white fuel pump relay, then pry off the case and again look for signs of hot contact areas inside, also using a magnifying glass see if you can see pitting on the relay coil contact faces. At the age of these cars, the fuel pump relay can be considered a wear item. Worn fuel pumps can start to overheat what would otherwise be an okay relay and speed it's demise. Re-flowing the solder at the main joints can restore relays that have cracked and failed through repeated thermal expansion, but I can't imagine that being the cause of vibrations. The small cube fuel pump relays are basically non-repairable in my experience.

Another distinct possibilty is plastic vibrating in the lower console area, such as the relay tray in it's holder frame. Just having had your hand in the relay area may have momentarily shifted plastic conntact. Push down or in on the sides of the relay tray and frame to see if the sound changes. Note the little plastic fuse puller on the right could be hanging half in mid-air by it's plastic cord and the plastic vibrate against anything there. There's lots of other plastic, cables and wiring in that area that could also vibrate with road speed.

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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi,

Careless removal of relays by rocking back and forth can spread open relay
socket pins. Relays should be removed carefully, prying from the bottom
or better by using a relay extraction tool such as Lisle # 46950

https://www.ebay.com/itm/126221472190

There's cheaper options from you know where, and you take your chances.
Loose relay socket pins and or bad internal connections in a relay can cause
arcing with high current DC circuits. This can lead to toasted relays and/or relay sockets and finally start blowing fuses.
If the relay coil contact is loose you might be hearing the relay coil
cycling the points at high speed, a poor mans buzzer.
See my post near the start of this thread.

Bill

additional info.

1. the sound starts on cold engine startup as soon as i reach 28mph.
a. sometimes at higher speeds the sound disappears or seeems to
2. heater controls make no change on or off
3. headlights are off when this occurs if put on no change


the relays i had not though about and will check this possibility out today (sunday)

windshield molding is securely tight

i am thinking maybe something in the cluster... i have 2 working complete spare ones and will swap one out to see

relays my gut tell me other than cluster maybe my best shot

i will report back

Dear trichard,

Hope you're well and stay so. Check things - especially sheet metal - exposed to airflow.

Among these:
(a) heat shields on: (1) the exhaust manifold and (2) on the catalytic converter.
(b) exhaust system hangers.

A piece of loose metal - or plastic (e.g., grille, etc.) - exposed to airflow may start to resonate at 28 mph. But if metal heats-up, the expansion may just be enough to disrupt the resonation.

Hope this helps.

Yours faithfully,

Spook

You say your have determined the sound is from behind the dash but I decided to respond with my somewhat similar experience.

I had a buzzing sound that came on in the 30mph range in our 89 740. I eventually found that it was the stainless trim that surrounds the windshield.

I eliminated the buzzing by inserting a thin piece of plastic (cut from a parking pass that hangs from the rearview mirror). That "loaded" the edge of the trim and stopped the flexing that was allowing the buzzing.

Randy

--
Any twenty minute job is just a broken bolt away from a three day ordeal

Hi Randy,

Are you still having trouble logging in?

Today I switched to Quad9 DNS service for a test drive:
goto https://www.quad9.net/ for info.
and with the new DNS I enter www.brickboard.com/RWD
and it takes me here:

http://ec2-18-216-8-63.us-east-2.compute.amazonaws.com/RWD/

This looks just like Brickboard, but I can't login
without typing the URL in the Mozilla URL field, DNS weirdness.

I'm getting lots of creepy amazon popup windows with my Mozilla browser
and none from Netsurf which isn't full of call home junk you get with
Google infested browsers.

What browser are you using?

Bill

Hi Bill,

I use Chrome. I hadn't needed to login for some time, but after clearing my history I found that I was not able to. However, now I find that I can login. I don't have and explanation.

Randy
--
Any twenty minute job is just a broken bolt away from a three day ordeal

Hi Randy,

Here's some explanation or made up excuse by industry for what happened here.
It's hard for me to believe the "Virus story" with main stream browsers being so privacy invasive.

https://www.malwarefox.com/amazonaws-virus/

The bad behavior may be confined to a specific Mozilla browser here, and now
things seem to be working normally?

Bill

Unfortunately, I'm afraid it's often inconsistencies due to Jarrod's cookie handler. This has been an on and off problem for decades whenever Jarrod makes a change to the cookie layout, which he has apparently been doing lately. I use various versions of four different browsers over four devices to access the brickboard and occasionally have these types of problems. Mostly it's with versions of the Mozilla-based Firefox browsers, both PC and iOS, but sometimes also Chrome and once even Safari. In the past year I've had at least three occasions where all I get is 404/403 errors as if the website was down in addition to the occasional unexpected lost signon and problem logging back on. I've even told Jarrod the site is down and he obligingly restarts the server. That may not always be the problem, but it's at least guaranteed to reset access to the user database.

The fix that works more often than not is to clear all permanent and temporary browser cookies that contain "brickboard.com", exit your browser to be sure temporary cookies are reset, and sign back on. Although rare, if you use multiple devices and browsers you may need to first go into each and signoff the brickboard. Unless you're good with your browser advanced settings you may need to clear all cookies and lose all curtrent website signons and access preferences. Jarrod once had a web page script you could go to that reset just your brickboard RWD browser cookies, but I just tried it and I don't think it works anymore. If you still have problems signing on, click on the home page link and try coming back in that way. If it continues to stay knotted then make a new anonimous post that you're still having problems after having deleted cookies. If I spot enough of those I'll rattle Jarrod's cage, which I try to avoid as he's a busy guy and the brickboard is no longer a personal priority of his.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

I thought about telling the OP about that, but it was mostly just a 700 issue. My '89 developed that problem at highway speeds. You could identify the area by selective use of taping various areas of trim, usually the upper area of the side moulding strip. Volvo actually had a TSB about vibrating/whistling windshield trim in 700s. As I recall, for customers who came in to complain about it, the fix was to slip a trim tool under the moulding at the mounting points shown in a diagram and turn (counterclockwise?) the square plastic mounting clip a bit so the plastic fingers stuck out properly to grab under the lip of the moulding. By the time I read that, I'd already shot silicone sealant underneath to end the problem.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

All kinds of possibilities I can think of for buzzing/vibration sounds in the upper center console region.

First, have a passenger verify where the sound is coming from. I've been misled many times guessing where a noise is coming from at road speed to the point of being almost certain, yet out by 2-3 feet. Even better, give them a mechanic's stethoscope or hard piece of plastic/vinyl tubing to hold close against (not in) their ear to find the loudest area. Once you've got that more precisely narrowed then try to make it temporarily go away by pressing on things, moving things a bit, taping things together, whatever it takes to make things a bit different. You know your car best, so make yourself the passenger.

o Does it vary by road surface? if not then possibly a relay buzzing that normally doesn't buzz. Try turning off your headlights at speed. Access the relay tray and wiggle/reseat all relays then try driving again. Drive with access to the relay tray open and put your fingers on each relay -CAUTION some relays run very hot, consider gloves.
o Operate the heater controls, air vents, move/press on the louvered dash vents, and vary the fan speed.
o Press/push on the defroster vent(!!) plastic bezels and the windshield trim
o Open the glove box, push on all sides.
o Push on the switch panel, especially the thin trim around the heater control panel.
o Push on the console side panels and under dash panels

Those are the kinds of noise areas I've encountered over the years in 900l/700 dashes.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

> Drive with access to the relay tray open and put your fingers on each relay
> -CAUTION some relays run very hot, consider gloves.

What relays run hot without some issue with a faulty connector?

Loose Relay pins arcing might be the noise he's hearing.
It should be accompanied with some toasting of the relay socket.

Loose female pins are easily tested, adjusted or replaced.

Make a test gauge out of a 1/4" male blade connector crimped on a stiff wire.

Make a pin extraction tool by grinding a long taper straight slot tip on
a stainless ten speed bike spoke.

Get new pins from www.davebarton.com

Best regards, Bill

Exactly, I should have finished that thought and said any hot relays indicate a potential problem and can lead to melted and deformed relay sockets if it hasn't already started to happen. The top of any of the high current load relays may often be found warm under normal circumstances, but should not be hot. The fuel pump relay, especially the small Hella cube style as I recall, and maybe the headlight relay are often good and warm after a long trip. Things like worn fuel pumps and using high wattage headlight bulbs can aggravate the situation. It's actually worth occasionally checking for that so you know it's time to pull out and inspect the relay tray, including underneath.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now