What is this gauge and what does it measure? It shows the BAR letters and the numbers 1, 2, and 3. I know it is not barometer!

Would BAR be relative to ambient atmospheric pressure at elevation?

Or absolute like PSI / BAR as with engine oil pressure the oil pump delivers that the oil pressure gauge displays?

Yet BAR may also be absolute pressure referencing ambient atmosphere at mean sea level of 14.7 pounds no matter the elevation Volvo 240 (and other RWD Volvo with such operating gauges) such as 6000 to 8000 feet in Santa Fe, NM?

Sort of more confused now whether absolute or relative to ambient.

https://en.wikipedia.org/wiki/Bar_(unit)

That's a nice dash with all them instruments!

Thanks.

--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity

" I know it is not barometer! "

Technically speaking, it is. But pointing that out just makes me the smart-aleck nerd you want to beat the crap out of after class.

The two right-most gauges are both "barometers," one designed to measure oil pressure, and the other, boost pressure. Are you installing it?




--
Art Benstein near Baltimore

My wife and I were happy for twenty years; then we met.

Hello again Art,

Nowhere on my schematics does a red wire show that connects to the BAR sender. They all show a single green wire.

But I do have this broken connector on the sender that connects to a red wire. I think it was broken and then soldered back on and that is what I plan to do when I start to put everything together again.

The red wire joins its green companion and a black wire that connects to the alternator and all three of them head off to the other side of the engine. They are bundled together and then run through a larger bundle to the LH side of the engine.

I will try to send a picture.

Can't be sure, given the likelihood others have done repairs before you, but I think that red wire belongs on the alternator.

The sender, when factory installed will have a black wire for the oil idiot light, and a green wire for the gauge. The alternator has a small red wire for pre-exciter stimulus, the large red wire to the starter, and a short blue wire to ground its case.
--
Art Benstein near Baltimore

The taste of low quality lingers long after the satisfaction of low price.

Hi Art,

That conforms with my Bentley/Haynes manuals. Black to the idiot light. Green to the gauge. Hmmm.

I disconnected a black wire from the alternator. I am wondering if this wire has been incorrectly installed and should have been connected to the sender and the red wire to the alternator.

I am having the alternator looked at by a local automotive electric shop right now but it makes sense to me to connect the red wire to the alternator and the black wire to the sender. I will get a good look at the spade connector when I get the alternator back.

These three wires, the black, the green, and the red, are bundled together within their own plastic sheath. And they in turn are bundled with the all of the other wires in a larger plastic sheath.

I am wondering if the alternator could have worked without its red exciter wire. Not sure how long this mistake has been in place.

Wait a minute. I originally thought the red wire went to the alternator. What I need to know is whether they broken connector belongs to the alternator or to the oil sender. I have been assuming it belonged to the sender but it probably more likely belongs to the alternator.

Sorry to think aloud like this. But you have provoked a lot of thinking!

Thanks again, Art.

Bob

Hi Peter, er I mean Bob,

Just posted a reply to maplebones on driveshaft work and had your name in my head when I began the post. Using the edit feature, I fixed that.

Interestingly, the alternator would indeed work if the oil idiot light (black wire) was connected instead of the red one. No harm done, but the oil light would work as the battery idiot light.


--
Art Benstein near Baltimore

Life is like a roll of toilet paper.
The closer you get to the end the faster it goes.

Okay. I have emailed the shop so I expect a reply tomorrow sometime. In the interim I can get the oil sender functional and hook it up to the black wire. I will get back when I have more to report.

Thank you Al and all others who educated me on the function of this gauge. It came with the car when I bought it in 1992 and I figured it had something to do with oil pressure.

But it always would read 'hard over hot' [I was an instrument tech in the air force in another life] and was rarely showing anything other than that so I tended to ignore it.

Lately, it has been stuck in the hard over hot position until I tapped it with my keys to get it to rest position.

So, I am in the midst of getting the alternator looked at and installing new gaskets for the water pump and I noticed one of the leads to the two terminal sender was broken off. I am also changing out the bottom rad hose because I read somewhere it is a good idea to change them out from time to time.

I was going to change the water pump but when I realized it was the original Volvo pump and it seems to be tight and functional I decided to keep it and just change the seals and gasket [it had been leaking from the O ring style seal at the top of the pump]. Hey, a pump that has been going for the last 38 years should have another ten or so left in it. Right? I am a sucker for original equipment.

Anyways now I have another item to deal with. I plan to take out the BAR sender, clean it up and repair the broken connection. Keeping my fingers crossed that the sender itself is still functional. They are very hard to come by according to my local parts guy.

It looks like a bear to get out but I haven't gone under the car yet to see if I can get a better look at it from below.

I thought the sender was the oil pressure sensor and was corrected by my local parts guy.

Thanks again for your input, Art.

Bob

I thought the sender was the oil pressure sensor and was corrected by my local parts guy.


The sensor for the idiot light is not the OP sending unit for the gauge so parts guy is correct in that statement. But the sending unit installs in the same location as the sensor. That is, it replaces the sensor. Anything under the car or more specifically under the engine (a wire connected to the oil pan drain plug) would be for oil temperature.

I wonder if a previous owner installed the gauge and hooked it up to the idiot light sensor thinking that was all there was to it.


--
'80 DL 2 door, '89 DL Wagon, '15 XC70 T6

To expand on what bulletproof wrote---As far as I remember the multi-function sending unit (which can come as a 3 bar--or 5 bar sender depending on the gauge--Volvo used both) mounts with an angled adaptor fitting between the sender and the block. One electrical connector blade is for the warning lamp--the other for the gauge. I would think that the 3 bar gauge would stay pinned (approx. 45 psi) most of the time while a 5 bar gauge would normally read less than pinned. The base of the sender will have it's spec stamped on it if needed to check that it matches the gauge. -- Dave

Hi,

The gauge measures pressure in metric units. 1 bar = 14.5 psi

Peter

Thank you Peter. I understand PSI better than BAR.

Also the difference of PSI / Bar.

Not quite following you on this Nahtanha. Do you mean PSI minus BAR. equal the reading?

I would take it that it is a simple Bourdon Tube style instrument that measures PSI in some kind of barometric scale.

Bob

It is the oil pressure gauge.


--
'80 DL 2 door, '89 DL Wagon, '15 XC70 T6