Hi All,

I was in traffic, today, and noticed the temp gauge climbing. It got close to red line and the fans never came on. As the traffic cleared I was able to bring down the temperature with airflow and running the heater at max temp.

Anyway, got it home and checked the fuses. They're both OK (primary fan and secondary fan). So I'm thinking it's probably the ECT sensor (Engine Coolant Temp) on the water pump ('96 LT1).

Any other suggestions before I go to a whole lot of trouble over the ECT?

Many thanks!

 

What did your Digital Gauge read?

 

The analog gauge was at the second hash mark past 185 which would be about 235 degrees.
The Digital read out was 220 degrees.

At what temp should I expect the fans to come on?

I am assuming (yes, I know what that means) the ECT at the water pump sends the signal that drives the fans. Is that correct? I've paid no attention to the sending unit on the side of the block.

Is there something else that can prevent the fans from coming on? Something on the radiator or fans, themselves?

Many thanks for your input!

 

your fans are programed to come on at 225. From what you posted you are fine. To be sure start the car up let it run watch the digital gauge and the fans my quess is they are fine

 

About 228-230° your not running Hot, just a bit nervous! Let her idle up to the Fan turn on and observe the read out..

 

Thanks, Fellas!

I did a little research and found that the "secondary" fan switches on with the A/C. I've only had the car a week and today is the first day I can remember running the car without the A/C on.

So, I just started it up and turned on the A/C and, sure enough, the fans switched on! So, I know the fans work and I can manually switch them on if need be.

I will try your suggestion, above, and report back. I expected the fans to come on before 220°. Y'all know what wise men say about expectations!

 

Hook power up direct to the primary fan.

They go intermittently before they go for good.

 

Thanks, Brian.

However, I'm not sure I understand what you mean, nor which of the two would be the primary (as they both seem to come on with the A/C), nor where to put power to it as all of the wires are shielded.

 

You can not go by that analog gauge.
It does not have a linear scale, so you really have no idea what it was reading.
Switch to your digital temp gauge and see if the fans come on then.
They will come on at approx. 227°F (digital gauge)

 

Id consider replacing the relay.

 

Didn't know there's a relay in the system. Thought the ECT connected directly to the PMC. Where is the relay located?

Thanks!

 

Why should he replace the relay?
He does not know for sure he has a problem yet.

Yes, there is a relay.
They are located on the drivers side of the fan shroud.

But do as suggested earlier first, and tell us the temp reading from your digital temp gauge.

That needle on the analog gauge will be very close too (but not quite into) the shaded area on the gauge, when your digital temp gauge reads in the 227°F range.

1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)

Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.

 

I'm sure someone else would say this soon if I didn't - a factory service manual is an excellent investment if you plan on tinkering with the car yourself, especially for the things that are specific to your particular car.

 

I have a Chilton's and found out today, as you suggest, it's not enough.

 

I made the same mistake, almost useless except for routine maintenance, lol. The wiring portion is the worst part of those manuals, IMO.

 

Just back from eBay. Purchased the two volume GM set of '96 Corvette Shop Manuals.

Thanks for the recommendations!

 

DrDyno,

The FSM will be invaluable --- however, there are at least 3 different sections to review to fully understand the cooling fan operations. Please refer to your FSM for exact set-point temperatures for your 1996, pay attention as LT1 is different than LT4 settings.

1996 have two coolant temperature gauges and associated senders.

1. analog, on right side of dash, and driven by a single wire temperature sensor mounted in the passenger side head (closer to the fire wall).

2. Digital, displayed on center of dash, controlled by DIC 'gauges' button, and driven by a multiple wire ECT sensor mounted in the water pump.

If the thermostat and water pump are working correctly, there should only be about 10 degrees F between the two gauges. For example, if the analog gauge is at the 185 mark (first hash mark), then the digital gauge should read about 194. If there is a larger difference between the gauges, it could imply the thermostat is not the correct one, or has separated (lower section can separate from upper section) or it is failing.

There are differences between each year of the C4 -- also true in the way the cooling fans operate. Your 1996 has many improvements over older years.

1996 fans both operate together -- either both in slow speed (primary circuit) -or- both in high speed (secondary circuit).

1996 cooling fans are controlled via 3 relays mounted to the driver side of the radiator housing. The 3 relays are controlled by the PCM. the PCM used the ECT (water pump sensor) to determine the 'on' set-points (roughly 228 for 'primary' -and- 238 for 'secondary'). The PCM also used the A/C pressure sensor in determining when to turn on the fans (rough memory -- 180psi for primary circuit -- 260psi for secondary circuit).

With A/C OFF, the PCM should engage the 'primary' circuit so that both fans come on at slow speed at a digital temperature of about 228 degrees F. Should the digital temperature continue to rise to about 238 degrees F, the PCM will engage the 'secondary' circuit and switch both fans to high speed.

With A/C ON (and A/C system properly charged), both fans should almost immediately come on at slow speed and/or shortly thereafter switch to high speed.

Note, most of us drive during the summer and especially at stop lights with the A/C ON to keep the coolant temperature below 200 degrees F.

 

WHOA, Admiral! Many thanks for that info!!