Hi MacDuff,

>I found my 1991 240 has corrosion at ground collection that use a screw or bolt to secure to the plate or sheet metal. I did this service like in 2012 on all three 240s and all ran much better with better throttle response and improved fuel economy.

Which ground are you talking about here?
How did fuel economy suffer when it got squirrely?

> The (Penn?) Sylvannia silver star 9004 / HB1

Look here for some first class info from Brickboarder Ron Kwas:
http://www.sw-em.com/techarticles.htm

http://www.sw-em.com/Wiring%20Notes.htm#the_lowly_250_push_on_terminal

http://www.sw-em.com/Deoxit_D5_Additional.htm#my_recommendations

http://www.sw-em.com/voltage_drop_in_headlights_power_in_hex_connector.htm

Then ditch the halogens for better LED headlights

>I doubt there is something generating RF powerful enough in your 900.

Cars make lot's of RFI, plus RFI can come from external strong sources.
Here's an article about cleaning up noise so you can hear things better with a HF or VHF radio in a car, boat, or plane.

https://www.rfcafe.com/references/popular-electronics/eliminate-mobile-radio-noise-popular-electronics-june-1966.htm

This same noise can corrupt geriatric computers.


>Spare ECUs or newer versions of ECUs your model can use helps as well as spare relays. I have a half dozen white fuel injection and other relays, merely reflow the solder, and add moar solder so welds do not crack again!

Relays crap out with use and age. Solder isn't everything. If the solder melted, it's likely because the circuit has too much current. I'm not sure
if it's a fuel pump that starts drawing more current or if its loose main relay
socket pins that are the reason for too much current.
How much additional current flow for loose arcing relay socket pins?
(That cause the fuse block to crispy critter.)
The last poster that was blowing 30 amp fuses in 940 Fuse 1 couldn't bother to
measure current and/or look for loose pins and report back.
You should see 10.5 amps at fuse 1, blowing a 30 amp fuse there is crazy.
Especially as it's fused at 25 amps.

Proactive:
A simple way to check Fuel pump health is by measuring current at Fuse 1.
If its 10.5 Amps relax, if it's more then fix it,
if its 20 amps call the fire department.

>Easy to replace in the 700/900 engine bar! Sort of terrible in the 240 engine bay. The factory shop manual says 'pull the gear box' to replace this thing on 240.

You lost me.... engine bar?

Happy new year, Keep well! Bill

Great photo - Kitty 🐱!

There is no space to give you a thumbs up. Since I can’t give you a thumbs up any other way here is a double!!

👍👍
--
Will I buy another Volvo??? We'll see....

Hi Bill,
There's a good reason the CPS cable shield isn't grounded at both ends. It's a common misconception with coax applications and not necessarily intuitive. Art and I had a conversation about this here a couple of years ago where he provided a link to an excellent paper on the topic. If both ends of the shield were connected then stray currents may flow through the shield from ECU chasssis ground potential to the bell housing ground potential, thus possibly inducing current in the axial conductors, which is exactly what you're trying to avoid. Any RF hitting the cable gets dissipated by the shield to the chassis at one end of the cable and having two paths to chassis ground would make little or no difference.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

fyi-no hall effect sensor is ever grounded to the engine or elsewhere. the foil coax wrap on 3 is the ground to the ecm. i've found that when that shield is broken, it causes problems. BUT, i've always seen the outer jacket cracked or broken, causing damage to the shield. i've also had non-oe sensors cause problems out of the box, so it's oe or bougicord only, no other brand.