OK, so I got my 94 940 NA up and running and back on the road for the first time in 4 months. That's the good news. The bad news is that when idling, either in park or in drive, the idiot lights would periodically flash and the a/c blower cuts off.

It seems like an electrical problem, but I have no idea how to troubleshoot it or where to check first.

Please share any thoughts on this that you can. This happened on a dry day, and I haven't driven through any puddles (although I did wash the car about an hour before the test drive (hood was closed, and no water was sprayed on the engine compartment.

Thanks in advance!

Dear Wareagle32789,

Hope you're well. By "idiot lights" do you mean the warning lights at the bottom of the instrument cluster? If so, the problem could be corrosion on the instrument cluster ground which - if I recall correctly - is behind the plastic panel on the door-side of the driver's footwell.

That panel is secured by two, T-20 screws. To remove the panel, you'll need to remove the first two screws that secure the threshhold strip. These screws are under the rectangular plastic covers, which can be removed by lifting them with the tip of a small (1/8" - 3.5mm wide) flat blade screw driver or the tip of a knife.

The panel covering the ground plate has a long upper extension. The panel is best removed by sliding it rearwards (towards the driver's seat), while disengaging the upper extension from beneath the plastic molding. Go gently: old plastic is brittle!!

Another possibility is that the ignition switch is "on the way out". A faulty ignition switch can cause multiple malfunctions of the sort you describe.

First, though, clean the grounds. An aerosol electric contact cleaner - which dissolves corrosion - is helpful. I use DeOxit, but there are others. Do not rely on visual inspection: a layer of corrosion a few molecules thick - for too little to be seen with an unaided eye - suffices to block flow of current.

Hope this helps.

Yours faithfully,

Spook

Dear Spook,

Good morning, and thanks for the prompt response.

Yes, I meant that all of the various and sundry message lights on the bottom of the instrument cluster would blink on, at the same time the a/c stopped blowing.

When you say to check the grounds, do you mean all of them, or are there specific ones I should focus on? Electrical is not my strong suit. Should I just start checking and look for corrosion or loose wires?

Wareagle

Dear Wareagle32789,

Hope you're well. I referred specifically to the ground plate behind the plastic panel, on the door-side of the driver's footwell, at which the instrument cluster is grounded (black wire).

Unless work has recently been done in that area, there's no reason anyone should have touched any of the ground wires and so there's no reason why any ground wire should be loose.

However, over time, a film of corrosion can form that disrupts the circuit(s). You can clean the ground place - tack-welded to the body - with fine steel wool. However, the ground wire terminals are best cleaned with an aerosol corrosion remover, e.g., DeOxit. Follow the instructions on the can.

If all of the instrument cluster warning lights come on while you're driving - and stay on - that's a pretty sure sign that: (a) the alternator belt has broken or (b) the alternator has failed.

If the alternator warning light does not come on (briefly) at start-up (but all others do come on), the alternator malfunction warning light bulb has failed. If so, the alternator will not charge. The alternator requires a "micro-kick", i.e., a small amount of current needs to be supplied, to trigger the charging process. That current is supplied via the alternator indicator light bulb. Thus, if the bulb burns-out, the alternator will not charge.

Hope this helps.

Yours faithfully,

Spook

Spook,

I checked the instrument cluster, and the alternator warning light comes on prior to cranking (I think it's the one that looks like a battery, right?).

I am thinking that the alternator is on its way out, so I'm going to get it rebuilt.

Probably hasn't been done ever & car is at 199K, so it can do nothing but help the situation.

I will report back when the fresh alternator is back on the car.

Thanks,

Wareagle

Did you check the alternator output at the battery with a meter?

On checking for corrosion ...I also read that corrosion could get inside the cables coming to the battery, but I am also wondering if that affects us as badly in the south. I have checked for corrosion on a variety of rwd bricks I have owned, and the one I have seen it worst on is my red 240 wagon that spent it's early years on the west coast.

So I wonder if there is a difference in where the car has lived in regards to how bad the corrosion can be?? Probably not... just thinking out loud!

The '94 940 has to be almost tortured to die. The wife's '94 has 460k, and I surely wish we were back at 200k and had done better care from that point forward.

I wish you well, and I wish Auburn well... till the last game! RTR! 😊
--
"Do you think that's air you're breathing now'? (The Matrix 1999) '94 940T (463K+), 92 245 (300K+), 90 740 (148k)

OK, so I just put the rebuilt alternator back in to the car, and the previously-described symptoms have disappeared, EXCEPT that now the fuel gauge is reading empty and the light on the gauge is on...WTF?

Any ideas on what could be causing this?

Good luck to the Tide today!

Thanks

Dear Wareagle32789,

Hope you're well. I second Amarin's suggestion as to getting the fuel tank send unit into good working order. Use a fuel system cleaner to dissolve some of the paraffins (waxes) - normally present in gasoline (petrol) - that deposit on fuel system surfaces, and "gum-up" the fuel sender.

Because the send unit is stuck on "empty" i.e., the float is at the bottom of the send unit's tube (barrel), I'd add a full bottle of the cleaner and just five gallons of gas (a tad more than one-quarter tank capacity). A higher concentration of cleaner in the gasoline likely enhances results.

If possible, let the car sit for a couple of days. That will allow the solvent time to work. Then, add another five gallons of gasoline. If the float starts to move - and the gauge no longer reads "empty" - add another bottle of fuel system cleaner. Let the car sit. Then, fill the tank. I'd guess the gauge will show a "full" tank. If so, problem solved.

If not, then it will be needful to pull the send unit and clean it. Immersing the send unit's barrel in a cleaner rich in polyether amine (e.g., Techron Fuel System Cleaner) is likely to do the trick.

Hope this helps.

Yours faithfully,

Spook

Spook/Amarin,


I think that a direct attack on the sending unit/float may be in order.

Is this sending unit accessed from the trunk? I found a panel under the carpet in the trunk directly below the package shelf.

When I opened the panel, I could see hoses and a round plastic ring mounted at about a 90 degree angle inside this panel.

Is this the sending unit or some kind of fuel pump? Maybe I'm looking in the wrong place?

Years ago, I had a fuel pump go out on a 740 wagon, but don't remember if the sending unit was integral with the pump.

Please advise.

Thanks!

Yes thats the one under the panel. The whole unit is a sender with fuel pump attached by its side.

If you're doing this I'd recommend getting a replacement filter sock for the in-tank pump first.

Undo the plastic ring with hammer hits thru a block of wood to start it turning. If you use a screwdriver like I did you might chip off some bits off the ring. Disconnect the hoses too as the unit can't be pulled out without doing that. With the unit out you'll see a long plastic barrel - thats the sender with the fuel float disc inside. I used carb cleaner and repeatedly tip the barrel upside-down to make sure the disc is freely moving inside along the barrel.

The 940 uses a spring loaded fuel sender - the barrel was designed to extend itself out to the tank's bottom during installation. You'll have to compress (shorten) the barrel then tie it using string to make it stay that way. Insert back the unit (sender-fuel pump) into tank with the shortened barrel pointed at 4 o'clock position. Turn it down to 6 o'clock position and release the string. The barrel would extend right down to the tank's bottom. Install everything back in reverse order.

Be sure to do this at a place with lots of ventilation and disconnect the negative batt cable.



Regards,
Amarin.

Amarin,

Thanks for the info. I was able to convince my son to help me out, and between us, we got the unit out, cleaned up the float with some brake cleaner, and re-installed.

I now have a working fuel gauge!

Thanks for updating the board!

I think this repair should be in the FAQ.

Regards,
Amarin.

Hi,

That looks looks like you're low on fuel ; )

I think the in-tank sender still works but its float is stuck at the lowest point. The sender is a long tubular plastic with two resistance rods in the middle. The float has two holes in it which the rods run thru. The float electrically "connects" the two rods changing the total resistance depending on fuel level in tank.

I think the short way around this is to mix some cleaner with the fuel hoping it would also clean some deposits on the float to free it. The long way is to go on dismantling the sender from tank. You'll have to face the fuel fumes doing it this way. Don't underestimate the effect of fuel fumes. Bad headaches may come but if push comes to shove thats it. On the plus side you could replace the sock filter and inspect the rubber hose of the in-tank pump while you're at it. The last time I did this I used some carb cleaner on the sender to ensure the float moves freely.

Other methods? You may knock on the tank's bottom hoping that could free the float but I've never done this.

No I don't think you need to replace the sender. Its repairable.

Regards,
Amarin.

Hi,

Sounds like alt (power) issue. Had similar symptom previously when the carbon brushes worn short (but no blower cut off in mine). Have a look at those. Could be batt problem too if left unused for long. Recharge the batt by having a long nice drive or take it to a shop. Batt problem may be avoided by disconnecting it when car not in use.

While you're at it clean all main electrical connections - batt and alt power leads plus ground wires.

Usually power issues produce no OBD codes.

Regards,
Amarin.

Had alternator rebuilt & problem disappeared!

Hi Wareagle 32789,

Thanks for updating the board.

Regards,
Amarin.

Amarin,

Good morning, and thanks for the info. The battery was kept on a trickle charge, and there's plenty of cranking power, so I doubt that's the problem.

I will look at the alternator, maybe throw a meter on it to see what kind of output I'm getting at idle.

The car has 199,000 miles, and is probably on the original alternator.

Wareagle