Corsa dash in Monza = Temp sending unit?

[rnd5553]

I am installing a Corsa dash on my 66 Monza 110, and plan to use the Corsa head temp gauge. I have the thermister and the needed thermister adaptor from Clarks to be able to use the Corsa cluster's cylinder head temp gauge.

My question, how do you install the head temp "switch" that operates the idiot light since the thermister is in it's location now?

On Corsa dash the idiot light reads TEMP- PRESS. So am I to assume that on the 110 hp, I will only be able to operate the head temp gauge, and will need to forgo the idiot light, since there's no mounting location in the head now?

I assume the oil press part of the idiot light is on a different wiring circuit.

Also, when connecting the Monza dash harness to the Corsa cluster, I assume the fuel gauge will operate without having to change any wiring, is this correct.

Thanks

[cad-kid]

You could run an additional wire for the varister and install it in the other cylinder head. Each head has a mounting boss for the senders.

[66vairguy]

Brad will probably post some great wiring diagrams.

The Corsa overtemp switch works the same as the Monza. The switch is wired to a warning lamp just like with the Monza and uses the SAME connection at the instrument plug to the main harness. The only difference is the Corsa had two wires, one from oil switch, one from temp. switch that ran up to the dash and were united by a diode BEFORE connecting to the instrument cluster warning lamp. This was done because the Turbo cars got a buzzer for over temperature conditions AND the warning light. The diode prevented the oil pressure switch from turning on the buzzer whenever you'd started the car.

You don't need the "buzzer" so there is no need to change anything in the Monza harness for the oil and temp. switches. Just add the wire from the thermistor to the instrument cluster plug. Completely separate from the warning lamp circuit. There was NO wiring for the thermistor in the in the Monza wiring harness(es). You'll have to run a wire from the engine bay through the tunnel and up under the dash to the instrument cluster socket. If you don't have the socket connectors you can bypass the socket and run the wire directly to the temperature gauge. Not what I'd do, but many do.

BTW - over temp switch on one head, thermistor on the other head.

[bbodie52]

The engine compartment wiring for the Corsa, Monza and 500 warning light is identical for all three models. The only difference is the Corsa, with the thermistor in the left cylinder head, and its separate wire added to feed the temperature gauge. The additional wire from the coil negative terminal supports the tachometer. The vacuum/pressure gauge is mechanical, and is supported by thin nylon tubing. The clock is unlikely to be functional (they did not last long before failure), but the internal mechanism can be replaced with an electronic unit if you decide that you want a functional clock. The speedometer is a weak link. The odometer and trip mileage internal gear mechanism is usually worn out, and once it fails there are no new replacement components.

The attached CORSA article discusses Corsa speedometer repair.

Corsa Speedometer Repair - Communique - 2012 May - Vol 34 - No 4.pdf

Corsa Speedometer Repair - Communique - 2012 May - Vol 34 - No 4

(785.62 KiB) Downloaded 38 times

[azdave]

Short answer is that you can't use the existing single wire (that is shared by the low oil pressure switch and high temperature switch) for the new gauge unless you give up both of those features. Just run a new wire for the CHT circuit and put the thermistor in the other head. That's how everyone else does it.

[rnd5553]

So it sounds like I need to drill out and "tap" a hold in the driver side head to be able to mount the thermister? This is something I was trying to avoid doing. If this is really needed, what's the "drilling" process entail drill size etc? Thanks again

[cnicol]

No. Don't drill. I used to do that when I was a teenager and that eventually resulted in a ruined head because the drilled hole aligns with the head gasket. Instead, use the Clark's adapter which provides the needed depth and proper threads for the thermister. (The left head is already drilled BTW, it's just the wrong thread and isn't deep enough for a thermister)

[rnd5553]

Ok so Let me see, on a 110 the left head has a threaded hole already that I could install the thermister in using the adapter I have from Clark's, and then replace the temp sensor sending unit in the left side head. There is really no way to check these sending units to see if their still functioning properly is there? Thanks

[cnicol]

Both heads have identical holes.
Install the thermistor on the left head using a Clarks adapter
Leave the right head (and its temperature switch) as-is

Check thermistor with an ohm meter. If it reads 5000-7000 ohms at room temperature it's good. Also check thermistor mountihg threads because they are often broken during removal. You can actually still use a thermistor with partially broken off threads; you only need about one turn remaining but of course full threads are better. Also check the threads on the wire terminal end because you need to be able to secure the wire well. Also make sure the stud is secure and doesn't rotate. If it rotates, that will break the internal temperature sensor.

[rnd5553]

Thank you but are you sure there a drilled hole there, I read that there's a Boss for the thermister that needs to be drilled out on the 110 HP left head.

[cnicol]

YES! There's already a drilled hole! It's just that it's not deep enough and has the wrong thread pitch. The adapter screws into the existing hole (has the correct thread pitch for the head) and adds needed depth and offers the correct thread pitch for the thermister. It's an ADAPTER.

[91blaze]

Both heads are completely identical. Just use the adapter, no need to drill.

[jmikulec]

Ok, how would I hook up the oil temp and pressure?

[cnicol]

Ok, how would I hook up the oil temp and pressure?

Temp and Press are already wired to the warning lamp on all Corvairs. Nothing needs to change when you add a thermister and head temperature gauge to the left head. (BTW It's head temp on 61-9 models, only 60's sensed oil temp)

[rnd5553]

Ok I'll have a look but the nice guys at Clarks told me there a Boss on the left head that needs to be drilled, hope they are wrong. Yes, I do have the required thermister adapter too. Thanks.

[joemonza]

Changing gears just slightly. I have a 1966 Monza with a Corsa dash installed (in it when I bought the car) and it is a 1966 140 horse. There shouldn't have been a thermister there as the original gauges wouldn't have needed it. Right? My question is would I need to use the adaptor from Clark's on a 140 as well if it's not a Corsa? I have purchased a thermistor already courtesy of Mr. Nicol. At the present time all that works is the speedometer and it is pretty much spot on.