I just purcahsed a '73 1800es. I'm quite happy with it despite a few cosmetic defects (slight rust both repaired and not). It handles well but it seems the wiring may be a mess (non functioning clock, radio, speedo). But I'll leave that for another post. What I am most worried about is that when at idle, the oil pressure gauges reads very low, close to 0; and the oil tempature gauge reads very high, into the red. I read that the oil temp gauge shouldn't get a reading until after about 20 minutes of driving, could this mean a bad gauge or bad oil temp sensor? After steady drivng the oil pressure gauge will almost reach 70, the red oil light still flickering, and the oil temp gauge will sometimes move all the way left indicating the lowest tempature possible. I am baffled, could it also be a bad oil pump or a clogged pick up screen? It makes me nervous to drive the car in this condition so any help would be greatly apperciated.

Thank You.

Adam.

/// Check the instrument voltage regulator. I don't have that mod but I have a 73 144. If the regulator fails the coolant temp will go high and the gas gauge will read high. Voltage on the regulated line should be 10.2 volts.

Long high speed cranking will zap the regulator. There is now a universal replacement from Volvo. It was $30 about ten years ago.

...I'm fairly certain, that since the original regulator was of a (slowly) cycling thermal element design, one would see either 0 or 12 Volts on the regulated output line, (the (long-term) AVERAGE of the line was 10V - this was apparently perfectly adequite for the instruments, which have an extremely slow response time). I gutted my 1800ES's when it failed, and replaced the thermal element with a modern fixed output electronic regulator. I would expect that's what the ones available from IPD have.

As far as the symptoms after failure...I would expect there to be two sets...one for if it failed at 0V output (supplied gauges would read zero) and one for if it failed at 12V output (guages would read high).

Hope that helps.

/// I am absolutely sure about my 73 144, I didn't have a 73 ES. I do have a 72 ES and since the gauges are not the same as on the 140 I would expect the regulator to be different. The circuit to change that mechanical regulator to the three pin electrical regulator is in the 1800 list archives.

I remember borrowing the regulator from the 73 to put into a 79 240 I had just purchased, (10 years ago).

My wife went out one wet morning and cranked the 79 until the battery started to die. The regulator was blown when I went out to stop her.

The failure of a regulator would still be a likely candidate. It should be eliminated as a problem source before tearing out wiring.

L K;

Did you ever figure out why cranking caused the regulator to fail? The regulator failure may just have been coincedental...it sounds like a stretch...or do you have some other information that suggests a link.

Cheers

/// I know why. A starter or other heavy electric motor generates spikes of voltage that can damage electronic circuits. This is, in part why you put a surge protector on your computer. There is transient and spike protection in the brake electronics of late mod Volvos.

It might help to put a surge protector or MOV on the regulated line but that would require a fuse also. MOV's and other protection devices work for the duration of the event (overvoltage or spike). They can dissipate huge currents for the short time period of a spike but would fail in an overvoltage situation. If one fails shorted fire is a possibility. Aircraft protectors have fuses for that purpose. If an aircraft protection circuit blows the device is off line until the fuse is replaced.

I think you've already found the problem: bad wiring.