Griff2002

I'm trying to figure out why the problem only occurs when the engine gets hot? I am assuming if it is a connection or shorting problem that it would occur cold or hot. But maybe something is happening in the sensor when it gets hot?

FireballXL5

Absolutely a good guess... Perhaps it's grounding itself out on the side of the unit and interrupting the ohms signal? Think Wilcox pointed out there's a cardboard tube in there... Perhaps it deteriorated and is allowing grounding? All signs would point towards the sending unit in my opinion... I'm trying to track down a new one myself as my temp gauges haven't worked since I bought my vette last summer... ;-)

AirBusPilot

It's a new motor w/AFR heads. It might be a thread contact issue, but I doubt it. We'll see when the new sensor arrives. I'll update.

0Willcox Corvette

I wanted to update this after talking to our electrical engineer... The oil inside the sender is not something to play around with. It's more than likely pyranol which contains pcb's.

FireballXL5

So... After striking out with the 'quick local' search for finding my sending units... I would like to find out what I DO have, and where I can buy new ones... Don't have a lathe, so I'm not going to try and rebuild mine... But now I'm curious how to find the ones I need...

I'm hoping I don't have to pull em out to find part numbers.. This is the temp gauge sending unit on the drivers side...

FireballXL5

This is the oil temp gauge sending unit on the passenger side...

DucatiDon

That second pic isnt an oil temp gauge...looks like a temp. activated fan switch.
Oil temp would be in an oil passage, not a water passage in the head.

FireballXL5

Lol. That makes faaaar too much sense... Lol. It is connected to the aux elec fan... I'll dig deeper to 'locate' my oil temp sending unit... I'm such a noob

M A Fry

Hey Willcox do you have a test proceedure for the amp gauge in a 69 vette?

Mark

0Willcox Corvette

That is the Auxiliary cooling fan switch that turns on your electric fan. We should have the switches you need on the site. What year is the car.


@ MaFry.

I have a tester here for that, but for home use.. The test is a simple one.. you use a double A battery and solder wire ends on it. If you touch one end to one terminal, and then briefly touch the other end to the other terminal the gauge should deflect... switch the battery around and it should deflect the other way.

If you hold the battery on too long you'll cook the gauge.. so just a quick touch and it should answer your question.

tejasak

This threads like this is why Willcox is the best. I saw this write up on FB and have to wonder. What possessed you to undertake this project?

FireballXL5

Mine is a 1981 corvette(built. Oct 1980) with a transplanted 383 crate motor... I'm looking for the water temp, oil temp, and aux fan sending units... ;-)

0Willcox Corvette

Seems odd that they would all be bad... have you ohm'd them out to make sure first. You really should remove, clean the senders and re-install... Then clean up those wire connectors. The top one.. the connector should be pointing straight and not downward. I'd remove that crimp on end, clean the wire and put a new end or connector on. Same goes for the fan sender.. if the old connector is worn out, you'd be better served with two spade terminals and some clean connections vs. what you have.

Water temp is no a problem except it won't give you an accurate reading... this one, 81-84 is closer than any of the other temp gauges I've tested. If it doesn't read correct I have a fix coming for that soon...

http://willcoxcorvette.com/product_i...oducts_id=5014


The oil temp is off the charts high, and there is an imported version with the gauge that is cheaper...
http://willcoxcorvette.com/product_i...ducts_id=27961


The aux. fan switch is discontinued..
http://willcoxcorvette.com/product_i...oducts_id=6586
and looked like this.

0Willcox Corvette

You know... That’s a very good question. I must say the leading factor was to prove a point. But we've been doing this for a long time, I just decided to publish this the next time we needed to do one. (This past week)

As mentioned above, I've tested every brand of sending unit available on the market place and I've even had manufacturers tell me their unit had the oil in them just like the originals... And when I pop the cap off I find them dry.

Most manufacturers (aftermarket and repro) don't know the issue isn't the oil.. (Yes I'm sure the oil helps conduct heat through out the entire sender) The issue is the Thermistor in the sending unit not being calibrated correctly. The temperature gauge is a non linear gauge and so the Thermistor must follow this same pattern...

When you are fixing a car in your shop, your name stamp kind of follows this repair. If a customer comes in wanting a temperature gauge to read correct... the only solution (for now) is to do as we've done above. While it might not be pretty... it works! Sadly the equipment required to do this is not something most would have in their garage though.

Since the gauge is non-linear, placing resistance in the sender wire is not the answer... Aftermarket senders tend to read cold... And to make the read higher you have to remove resistance. (put a resistor inline) Even if this were possible, it would make the gauge accurate at only one temperature and not over the entire scale.

So.. Where is all this going...

There is a solution and I will have it soon. I posted a picture of the last prototype on the fb page a few weeks ago and I’m waiting for boards right now. When the boards arrive the fix for the reproduction senders will be finished.

Willcox

FireballXL5

Many thanks! And I will do as you suggested and try to clean em up as best I can... Will also try and run some 'tests ' on them when I have them out... See if I can effectively bring these units back to life... ;-)

0Willcox Corvette

I just saw this post.. this thing really got popping.

Some aftermarket senders go berserk when they get hot... this may be your problem. Original senders are kind of easy to ID by the markings.

Willcox

Griff2002

Thanks. I'm going to replace it and see what happens. I haven't removed it yet, but from the outside it appears original. It was moved to the intake manifold, presumably because the AFR heads have the smaller threads.

0Willcox Corvette

The move won't hurt anything...

Griff2002

None of the original markings as shown in the pictures. And yet it doesn't look like the current aftermarket senders. I'd guess it was replaced long ago.

M A Fry

Thanks Willcox