Hemmings technical comments

[Barney Eaton]

The September issue of Hemmings (Howe -to, page 83) there is a question from a Corvette owner about temperature gage problems.

He put in three different sending units and after the car warmed, the gage would peg to HOT.

Jim Howe the Hemmings technical writer, contacted John Wolf at John Wolf Instruments about the problem.

Bottom line, GM's supply of parts (and probably those from other sellers)

are coming from China. John Wolf said that he is finding a need to "tune" the sending unit and gage. By putting a rheostat in the line and with the backup from a infrared temp unit, adjust the rheostat to get the gage to read correctly. Then measure the rheostat setting and put a resistor in the line with that resistance.

I liked the comment " GM has decided that China can somehow build these components to a higher standare of quality than US Manufacturers. (it couldn't be the price, could it?)"

The above could be contributing to problems we have on Reattas..... I know one person that sold a perfectly good Reatta because, the temp gage would peg, when the car got to running temp.... he had checked or replaced several things and confirmed the car was NOT running hot, he just could not stand the gage lying to him.

[Blue90]

Being lied to by your dream car can be a heart-breaker!

[KDirk]

A very good point here. The thing is, this is an electronic problem that can be compensated for, provided you have the knowledge. The bigger issue is mechanical parts (like wheel bearings just as an example). No way to compensate for **** poor quality in those parts, since you would need a smelting operation, a machining operation and who knows what else to correct substandard parts, or roll your own.

And what about truly critical parts - oil or water pumps, if these fail you can quickly and easily destroy an engine. Since the weasels (oops, I mean lawyers) have crafted bullet proof warranty language (for the company, not the customer) do you think an engine rebuild would be covered? Of course not. But they will gladly give you another garbage part to put on your now blown engine, since that is what the warranty says they will do - and all they will do.

So, we are increasingly at the mercy of companies who have decided to sell us garbage, since it is apparently the only way they can turn a profit. I think that says a lot about the current state of things, and none of it good.

KDirk

[Guest steveskyhawk]

Sounds to me that installing the correct resistor would do the trick provided the sending unit/gage resistance function was linear. Padgett?

[Guest Mc_Reatta]

Sounds to me returning the defective sensors to GM and telling them what they can do with them and buying ones from an another aftermarket supplier that bothers to make ones that conform to specifications would do more to end the BS, rather than trying to make do with junk ones.

[stealthbob]

Sounds to me that installing the correct resistor would do the trick provided the sending unit/gage resistance function was linear. Padgett?

That's a good point...your calibrating at one point but if the signal is not linear you will be only accurate at that specific spot.

[padgett]

GM gauges have never been linear and senders fail often. I have had oil pressure senders (my bane) fail high, fail low, fail open, and leak. There was even a TSB on the sender. I always keep a spare around. Even the FSM says to use a mechanical gauge if suspect.

Major issue is that the "L" uses a different range than the "C" and if you put an "L" sender in a "C", it will "think" midpoint is 60 psi not 40 psi and read low on a "C".

I would not correct with a resistor, I would correct with a different sender that fit the thread and read correctly.

BTW if I had a sender that pegged almost immediately, I would suspect that it was a switch mislabled as a sender but would not be surprised.