temp/pressure light

[lisascorvair]

In the last few days the temp/pressure light has come on. The oil level is fine, the fan belt is tight. The oil pressure switch is fairly new. If i increase the engine rpm the light will flicker Any thoughts? I really dislike idiot lights for obvious reasons,

[terribleted]

Check the oil pressure. If it is below 10PSI hot and idling you likely have an oil pressure problem (switch turns on around 7PSI). Most times the light staying on is caused by a faulty switch or light wires shorting to ground in the engine bay. This circuit has temp and pressure warning switches both feeding the bulb in the dash so be sure to check the wires from the engine harness to each switch for frayed spots or spots where they might be grounding to the engine sheet metal. If you and stated what car you were working on I might have been able to point ta a couple specific spots to look for the short. If the wires look good and the oil pressure checks out OK replace the switch.

The fan belt has absolutely nothing to do with the temp pressure lamp. Of course if the engine is operated with it off it will overheat, but, the temp switch will turn the light on at 525 degrees head temp if the switch is good, so the belt on or off is not directly related to lamp function. If the belt is off or loose it can readily effect the gen/fan warning lamp however.

[bbodie52]

Welcome to the Corvair Forum!

You did not provide any details about your Corvair model year, engine, transmission, etc. Those details can sometimes help with diagnosing the problem or with making recommendations.

There are two warning lights — GEN/FAN and TEMP/PRESS. The temperature/pressure warning light system is a relatively simple warning system that is connected to two warning sensor switches. Power is provided from the ignition switch to the instrument panel bulb, so turning the key ON without starting the engine provides a ground via the oil pressure sensor switch, which serves as a lamp test which illuminates the warning bulb until the engine is started. A GROUND provided by EITHER warning switch at the engine will cause the TEMP/PRESS warning light to illuminate, but the light does not differentiate between a ground at the oil pressure switch (next to the generator/alternator) or the cylinder head temperature warning switch (mounted in the right cylinder head, adjacent to the exhaust manifold).

In the illustration below, the area where the wiring passes through the engine sheet metal and connects to the cylinder head temperature warning switch is sometimes a problem. If the wiring is not routed correctly, and if the insulation on the wiring harness is damaged or pinched by the sheet metal, it may be accidentally shorting to ground and causing the warning light to illuminate. A faulty switch at EITHER location is also a possibility. Temporarily disconnecting one switch at a time can help to identify which switch is causing the warning light to come on (if the cause is not a shorted wiring harness). The oil pressure switch is generally more common as a faulty switch. The temperature warning switch seldom triggers a warning light. (I have never had an over-temp warning light come on in more that 50 years of driving Corvairs). Unless a small animal creates a bed under the sheet metal shroud that blocks airflow over the engine cooling fins, a Corvair engine seldom overheats if the cooling fan is operating. A failed fan belt would normally produce an immediate GEN/FAN warning light, causing the driver to shut the car off immediately — before the engine overheats.

» Sun Aug 15, 2021 11:06 am

In the last few days the temp/pressure light has come on. The oil level is fine, the fan belt is tight. The oil pressure switch is fairly new. If i increase the engine rpm the light will flicker Any thoughts? I really dislike idiot lights for obvious reasons,

Which light flickers?? The flickering of the TEMP/PRESS warning light when you rev the engine may be an indicator of an intermittent short to ground — a short that is being disturbed by increased engine vibration as you rev the engine. Faulty oil pressure warning light switches are sometimes manufactured. If you recently replaced the oil pressure warning light switch, the new switch could have an internal fault. Temporarily disconnecting the warning light switch wire should help to confirm that the oil pressure warning light switch is the source of the ground that is causing the light to illuminate. An actual loss of oil pressure would be unusual, as long as there is no major leak and the oil level in the engine is at normal levels.







This is a picture of the cylinder head temperature switch in the passenger side head. It is wired in series with the oil pressure warning switch that is normally found next to the generator/alternator but was initially installed on the right engine case, below the cylinder barrel near the head temperature switch on the earliest Corvair engines. The closure of EITHER switch will cause the TEMP/PRESS light to illuminate.


The link below will provide you with a list of useful websites that are Corvair-related. Some of the links will lead you to an extensive technical library that will allow you to download shop manuals and other technical references in Adobe Reader format at no cost. There is also a link that will help you to locate nearby CORSA (Corvair Society of America) club chapters. You will also find a list of essential Corvair parts suppliers. Clark's Corvair Parts in Shelburne Falls, MA is the biggest and oldest Corvair supplier in the world. You will find a link that can provide you with a series of videos that amount to a tour of the Clark's Corvair Parts facilities. Parts suppliers such as this truly make our Corvair hobby possible.

Common and Useful Corvair Websites

Corvair Forum http://www.corvairforum.com/forum/viewt ... 225&t=6007


I would like to encourage you to expand on your initial post and tell us more about yourself, your Corvair interests, and your goals for your Corvair. If you can describe your personal assessment of your mechanical skills and abilities, that would help a lot. Members of the Corvair Forum love to be helpful in assisting other Corvair owners with technical support and advice, but it helps a lot if we have some understanding of your technical background and mechanical abilities, Corvair-related knowledge, etc. Helping us to know more about you will help us to write comments to you that are tailored to your needs and experience. Knowing your location may also suggest some helpful ideas.

[lisascorvair]

My bad. 67 Monza Convertible , 110 hp engine, auto trans.

[gbullman]

You need to verify it is or isn't oil pressure as soon as you practically can, low or no oil pressure can do an engine in pretty quickly. If your fan is operating and there is no blockage of air passages under the shroud it is pretty unlikely it is actually getting to the 525 degrees that causes that switch to close and even if it were that it would take a while to get there.

You can test for a short (likely intermittent with what you describe) by temporarily taking the connector off the oil switch (just don't let it touch ground). If the light is still on or flickers the same that kind of rules out the oil pressure switch and indicates a short or possibly a failed temperature switch (which I'd be surprised if it failed in that manner). If it stays off under the same conditions the switch is at least suspect but then you really need to measure the pressure with a gauge to be sure. This one should thread in where the switch is now (may need some brass fittings to raise it up to clear other items); https://www.amazon.com/LSD-TUNING-USA-P ... ve&sr=1-15

Good luck figuring out what the issue is.

[terribleted]

My bad. 67 Monza Convertible , 110 hp engine, auto trans.

Primary spots to look for wire wear are where the oil sender wire passes behind the distributor and where the head temp switch wire passes through the R rear vertical shroud just to the right of the harmonic balancer. The temp wire can also short against a nearby pushrod tube as well. If you do not find a shorting issue then, you can try replacing the oil pressure switch. If the light is still on then you must get an oil pressure gauge, Remove the oil pressure switch and temporarily replace it with the gauge and see what the oil pressure is. If the oil pressure is low then repair of oil pump or engine main bearings is likely needed.

[joelsplace]

Brad,
You posted a picture of the thermostat not the temp switch. You can see the temp switch connector at the top but not the switch.

[bbodie52]

I used a picture showing the oil pressure and cylinder head temperatures switches by themselves, a photo showing a view of the wiring harness connector plugged into the switch, and a drawing showing the wiring harness and pointing to the swtch in the head. I thought that would be enough.

I have added a close-up of the installed switch below.

[joelsplace]

That bottom picture is good but I think the top picture of the thermostat would confuse the person needing a picture.

[bbodie52]

Here is some additional engine heat information from Clark's...




https://ssl.corvair.com/user-cgi/catalo ... w_page=387

https://ssl.corvair.com/user-cgi/catalo ... ow_page=20

Different thread (coarse or fine-thread) listed for different heads...

Part number C438R: REPRO HEAD TEMP SENDER-61-69 (EXC TURBO & 140) COARSE THREAD-GASKET=C644 FOR IDIOT LT

Weight: 0 lbs 4 oz
Catalog Page(s): 11(23),20(44),93B,183
Price: $ 33.65



Part number C437R: REPRO HEAD TEMP SENDER-62-69 TURBO & 140 FINE THREAD-GASKET=C644 RUNS IDIOT LIGHT

Weight: 0 lbs 4 oz
Catalog Page(s): 11(23),20(44),51,93B, 183
Price: $ 39.80

[lisascorvair]

UPDATE: Before embarking on a anything else, I decided to replace the sending unit. $7.04 later, the problem was solved. This is the second vehicle in the late six months that I didn't get two years out of sending unit.

[bbodie52]

I assume you are talking about the oil pressure switch, the first of which turned out to be faulty? I have heard others say that these inexpensive switches can have manufacturing faults that can cause them to cause false error lights, not work at all, or leak.


Part number C484: OIL PRESSURE SWITCH-THIS IS NOT TEMP!!!! SPECIAL SOCKET=C5274 (MAKES EASIER)

Weight: 0 lbs 4 oz
Catalog Page(s): 11(24)
Price:
1 - 2 $ 5.95
3+ $ 5.30

If you want both a gauge and idiot light, then this is the sender you need!

If you want both a warning light signal ground switch and an oil pressure gauge sending unit, this dual-function unit is a good substitution...

VDO 360-009 Oil Pressure Sender
https://www.amazon.com/VDO-360-009D-360 ... XEBG&psc=1
https://www.summitracing.com/parts/vdo-360009#overview
VDO 2-1/16 Oil Pressure Gauge, Cockpit Series
https://www.amazon.com/VDO-Pressure-Gen ... 783&sr=8-2
https://www.summitracing.com/parts/vdo-350040

[gbullman]

UPDATE: Before embarking on a anything else, I decided to replace the sending unit. $7.04 later, the problem was solved. This is the second vehicle in the late six months that I didn't get two years out of sending unit.

Great news, that is by far the simplest fix!