Gents, I am in need of assistance.

My girl has a 93 850 that we purchased about a year ago. The car had 90K on it and we were thrilled with it for the price.

However, over the winter, both the Low Oil and Oil Pressure light started to come on and go off intermittantly. If you would hit a bump or expansion joint in the road, the light would go on or off. Now, they just stay on.

The car is dealer serviced for the oil changes and has never had a problem with using or blowing oil.

The car did have a rebuilt head on the car when we bought it, the car didn't have a timing belt changed it's entire life, and at approx. 89,800 miles, it snapped and bent a few valves. The car was bought by a dealer for a song who had it fixed from a reputeable shop (I have all reciepts and works orders) along with other small things (sunroof motor, headlight wiper, etc.)

After talking with a few folks (Volvo dealer service, NAPA, local foreign car parts fellas {who are Saab and BMW guys from waaaay back}), it was determined that the oil pressure switch was the culprit.

So, I take the cooling fan and shroud out and change the sensor, check the coupling on the wire and the wire to see if it is broke, all are fine. I replace the sensor, button it all back up, and "sh*t" is all I could say. The lights were still on. I topped off the oil (yeah, yeah, I wasn't thinking and dribbled about 1/2 a quart on the garage floor when I took the old sensor out LOL) and waited for 15-20 minutes and tried again. Still on. I undid the battery, waited another 30 mins to see if the ECU would reset and viola! Still on and now the radio won't work (silly radio codes..."Hello, Volvo dealer service...I am an idiot...").

So, anyone have any idea?

The oil pump was ruled out by the Volvo dealer. If the pump was or is bad, it would be a big bill by now, but it's been 6 months and no problems. Castrol semi-synthetic every 3K at the dealer.

My girl is easy on the car, so I am not sure what the hell is up.

If anyone says eletrical, pleae give me something to go by. Electrical in an automibile is a blackart to me, unless it's a Mustang.

Thanks for any and all help.

Matt

 

The 93 models were the only ones that used a oil level warning light. I did dig up the schematic of the circuit and it appears that there is a diode in the control module that will illuminate both lights (Low oil and oil pressure) if the oil pressure sender reads low. It is not as clear as to what happens when just the oil level sender is triggered.

At the end of the day it may be a bad control module. The control module is relay number 201 and it is located in the upper left corner of the lower electrical center. The lower electrical center is located inside the car, high on the firewall, just below the fusebox. It will be very difficult to get to that relay without removing the relays below it - it is a very tight fit.

If you are lucky that relay might just be loose since the problem started intermittently.

Here is the schematic:



The device key is:

4/18 - Relay 201
7/6 - Oil Pressure Sender
7/35 - Oil Level Sender
5/1 - Instrument Panel

...Lee

 

Hi lee,

During my electrical training here in Australia, I was taught all components on a wiring or schematic diagram are always shown (drawn) in the de-activated position.

In the schematic diagram you've provided, the contacts on both the low oil level and the oil pressure switches are both drawn in the open position and I assume when (a) there is sufficient oil in the sump and (b) the engine is running and the oil is pressurised (C) both of these contacts change to the closed position.

The diagram also shows both IP warning lights supplied with a common 12v + and the bottom side of the lights grounded through the switch contacts.

So according to the schematic, if the oil level and pressure were both O.K, the IP warning lights would be on constantly - but I know that wouldn't be the case.

What am I getting wrong?

 

Most of the schematics I deal with are drawn in the "normally open" or "normally closed" position based on "normal"- not in the failure mode -operation.The only thing I can think of is that the relay isschematically a "Black Box" and I have no earthly idea what it does if it is missing a signal or if it is missing B+ (Battery voltage). Matt said he changed the oil pressure sender so I doubt the replacement sender is bad.

I always take the easiest route first and then dig deeper as necessary. I wound up removing the entire dash to trace down the wires that had chaffed against the premium sound amplifier casewhich created a short in my Platinum that took out the field coil voltage to the alternator and caused dang near every idiot light on the cluster to illuminate.

In the end I could have done it without removing the dash but the dash mounts were broken anyway and the - USA - passengers side was flopping around and making just God awful noises at every bump.

It gave me an opportunity to deal with that.

I doubt any cares but I took some pictures along the way and did a writeup on the subject here:

http://www.matthewsvolvosite.com/cha...ic.php?t=15115


...Lee