Hello again: Have a 1993 Volvo 240 wagon. 185,000. miles. Auto Transm. B230F engine.

I’m still having difficulty with this oil pressure light problem (see previous posts below).

At the wiring harness connector (inside car, above passanger floorboard, where the fuel pump relay is) I cut the oil pressure sensor wire (terminal #17, black wire) on the connector and the light went off.

However, when I jumpered a wire from this point on the connector back directly to the oil pressure sensor (effectivly replacing and bypassing the bad wire) I still have a problem.

Something is not right.

With this jumper in place, with the ignition on, all the dashlights should light up. They all come on except for the oil pressure light.

Then after you start the car, the oil pressure light should stay on for about a second.

It does not. It never lights.

Any other suggestion would be appreciated.

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posted by Cliff Pope on Fri Jan 21 03:47 EST 2005

That's it Don, spot on. I had exactly that on my 93. The alternator cable was corroding, it got hot, melted the insulation, shorted through to the oil sender wire.

The alternator cable is of course live all the time, which is why the light came on even with the ignition off.

It is worth sorting out all the wiring there, and then re-routing it so that it isn't trapped behind the engine mounting.

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posted by Don Foster on Thu Jan 20 15:41 EST 2005

I'd bet a cold one that the oil pressure wire is shorting to the alternator wire where they come together behind the alternator or where the harness loops under the front pulley.

An older 240 would probably have a failing engine harness. Yours is newer and might have suffered a crushed or pinched harness, which could have punctured the insulation. (But I don't know how this would happen....)

Don Foster (near Cape Cod, MA)

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posted by Mr. Tool on Thu Jan 20 09:08 EST 2005

Hello all: I have a 1993 Volvo 240 wagon. 185,000. miles. Auto Transm. B230F engine.

I’m having a strange electrical problem.

When the car is shut off. No key in the ignition, the red oil pressure light on the dash is glowing.

When I turn the ignition on (not cranking) all the dash lights come on (as they should) except for the oil pressure light.

I have done the following so far:

1. Removed the fuse block strip, removed all the fuses, cleaned them, and cleaned all the connectors (fuse and spade terminals), front and back, and put dielectric grease on all the fuse connections and spade terminals and re-installed.

2. Cleaned the connector at the oil pressure sensor on the engine block.

3. I believe all my ground connections are good, because I cleaned and dielectric greased all of them about 2-3 years ago.

One symptom recently (about 4 days ago) was a burning smell coming from the heat duct. I believe the large resistor on my blower motor is going bad.

Also, as weird as this sounds a weird buzzing noise intermittently came from behind the IP panel at that same time.

This occurred off and on for a day, and then stopped.

Even after these symptoms, it wasn’t until yesterday that the oil pressure light trouble started.

If you have any suggestions I would appreciate it.....Thanks...Mr. Tool.

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Mr. Tool

did you ever figure this out? I've had intermittent problems with car not starting, then starting fine. Now it starts, but 2 dash lights stay on when ignition off (oil being one of them). I read that the 850's had an ignition problem that caused dash lights to stay on
sbroughton335@gmail.com

Here is an update. I replaced the Oil Pressure Sensor (Switch) with a known good one. No change in the problem. My next plan is to keep the bypass wire (replacement) wire in place foir the oil pressure swith, and now to disconnect and bypass the small 12+wire at the alternator. Any additional comments would be appreciates. I have also pulled the IP out. All visually looks good, at first glance.....Mr. Tool
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Mr. Tool

Does the OP light still come on (Key Off) if the wire at the OP sensor switch is DISconnected?
It shouldn't, if that is the ground path allowing the light to come on.

If it does still light with OP wire off, disconnect the small red wire at the alternator (D+) and see if that changes the symptom.

For an Oil Pressure light with Key Off, there must be a bogus source of +12V on one side of the bulb — and a ground path on the other side (usually the normally closed oil pressure switch).

My wild guess is that the wire to the OP sender is OPEN (no light with Key ON), and voltage from somewhere (???) is getting on the bulb side of that "open" and feeding back "upstream" to the bulb.

The flaw in this theory is that there is no obvious ground path for this reverse voltage. But I have a hunch. . .
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Now that you have rerouted the wire, the oil light no longer comes on with the ignition off. Right? (Or does the same problem exist, as indicated by the subject line?)

If so, then if the oil light doesn't come on at all when hooked up to the sender, I'd suspect the sender. They're cheap to replace (I paid about $11 CDN for an Echlin sender from NAPA).
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1980 245 Canadian B21A with SU carb and M46 trans

Thats right, with the wire rerouted the light no longer comes on with the ignition off. HOWEVER, it doesn't come on with the ignition on either. Nor does it stay on for 1 second after the car starts. It could be that I had a wire shorting problem at the same time the oil pressure sending unit went bad. I will check into this possibility. I'm also leaning to maybe having a problem within or behind the IP. Based on my original posting I think possibly that the burning smell and wierd noise may be linked to this problem. Any more suggestions would be appreciated........Thanks again.....Mr. Tool
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Mr. Tool

IF you have an ohms tester check your oil pressure switch. With the engine off the sensor lead should read no resistance with ground. Or use a volt meter: attach one lead to the battery and the other to the the sensor lead with the engine off. You should get 12 volts if the switch is working. If the engine is running you should get O volts.