Hypertech thermostat and fan switch

[thirdtimevetteowner]

I just R&R'd my stock cooland temp fan switch for a hypertech unit, along w/ the cooresponding 160 stat. After the motor had run about 5 to 10 minutes max, the dash temp guage went from lo to 299. I unplugged it, and it reads nothing (as it should, I guess), but upon plugging it back in the temp guage did exactly the same thing (w/out the motor running even). Sounds like a direct ground somewhere to me. Possibly a faulty sender from Hypertech is my next thought. Any help would be surely appreciated. Right now I am waiting for the motor to cool enough to put the orig sender back in and see what happens, hoping it didn't damage the dash components. It could only happen to me, once more, or has anyone else ran into such a problem?

Rich K

 

[MPoore]

On my 85, the fan switch has nothing to do with temp readings. Assuming yours is the same, you might want to check wiring for the temp sending unit. There is one on the left side, which is easy to unplug, and one under the throttle body, which is harder to unplug. I think the one on the left side provides data for the gauge and the one under the t.b. is used by the ecm. Since you car has a different ecm, this might be different.

Please follow-up with the result.

 

[ecss]

If this is on an 89, the sender between cylinder 6 and 8 is used by the dash cluster for engine temp. display.

It has a spade lug push on connector.

If you have the optional Auxillary fan, you'll have a temperature switch located between cylinder 1 and 3. It has a single wire connector that you release by using your fingers to compress the connector and then it pulls off. The connector end on the switch end looks like a mushroom.

The Primary fan is controlled by the ECM.

So if you want the Primary fan to come on at a lower temp. you have to reprogram the Eprom or you can install the Hypertech switch in the head between the 1 and 3 spark plug and run an additional wire from it to the Primary fan relay Dark Green/Wire. When the proper temp. is reached. the switch will ground the Dark Green/White wire and turn on both the Primary fan relay and the Auxillary fan relay.

 

[Agent 86]

If this is on an 89, the sender between cylinder 6 and 8 is used by the dash cluster for engine temp. display.

It has a spade lug push on connector.

If you have the optional Auxillary fan, you'll have a temperature switch located between cylinder 1 and 3. It has a single wire connector that you release by using your fingers to compress the connector and then it pulls off. The connector end on the switch end looks like a mushroom.

The Primary fan is controlled by the ECM.

So if you want the Primary fan to come on at a lower temp. you have to reprogram the Eprom or you can install the Hypertech switch in the head between the 1 and 3 spark plug and run an additional wire from it to the Primary fan relay Dark Green/Wire. When the proper temp. is reached. the switch will ground the Dark Green/White wire and turn on both the Primary fan relay and the Auxillary fan relay.

Couldn't have said it better.

 

[thirdtimevetteowner]

Thanks to all for the help. Later that day, I figured out that where I put the Hypertech fan control was not where it goes (in the hole where the temp sending unit is, between #6 and #8 spark plugs, as noted in the instructions). Anyway, I looked between #1and #3, and there is a plug there, exactly where it would be if the heads were to be switched from one side to the other. The problem is, it appears to be smaller, although it shouldn't be.

I'm gonna attempt to remove it later today, but the fact that it's been there since '89 has me sceptical that it will come out w/out pulling the threads w/it.

So, ecss, if it is the same size and I can screw the Hypertech switch into it, then I can simply run a wire to the Green/White wire, once I dig it out and trace it to the fan to make sure it is the right one, correct?

One other thing. I have yet to hear the fan come on. Can I jump a wire directly to the fan to verify it even works, or does it have a relay that would need to be jumped? If so, where is it?

I really gotta get a service manual, but haven't had any luck finding one. Thanks again.

Rich K

 

[ecss]

It appears you don't have the auxillary fan.

The Relay for the Primary fan is mounted on the black plastic wheel well housing. It's right next to the front of the Brake Master Cylinder.

To test the Primary Fan, you short pin A to B on the Diagnostic connector located above the drivers right knee.

Connector looks like this.

[F|E|D|C|B|A]
[G|H|I|K|L|M|

Turn the ignition on (don't start the engine). The fan should come on and you'll hear some other noise which is the IAC seating in its bore.

I've heard people taking a socket extension drive and grinding it to fit the pipe plug in the head. Some people have had success in removing the plug and some haven't.
I've never heard anyone stripping the threads out. Usually the pipe plug head gets messed up.

The hole should be the same size as the one on the Passenger side head. When you get the new Switch installed run a wire to the Green/White wire of the Primary Relay.

The Primary Fan Relay has four wires. A heavy gage Red wire and a heavy gage Black/Red wire. When the relay closes, the Red wire supplies 12 volts to the Black/Red wire which goes to the Fan motor.

The other two wires are a smaller gage wire. The Dark Blue wire comes from the ECM ENG. fuse. The Dark Green/White wire comes from the ECM. The ECM grounds the Dark Green/White wire to turn on the fan. So all you need to do is run a wire from the New Switch and splice into the Dark Green/White wire. With the ignition on, if you ground the Dark Green/White wire, the fan should come on.

Make sure you disconnect the negative battery cable if you do any rewiring.

 

[thirdtimevetteowner]

ecss, just finished reading your last post to my earlier thread, and am impressed with how easy you made it all appear to be, now that I have read it. I think I can figure it out now, and can't thank you enough! It makes me wonder why some have aux. fans and why some, like mine, don't, which I didn't know until I read what you wrote. Anyway, now I can work on getting that plug out, to install the Hypertech fan switch. I am thinking I should get the Powermaster (I think that's the name) chip, to go along with the cooler stat and fan settings.

BTW, 2 weeks ago I finally got to make a couple passes at the "not too local" dragstrip. (It's about an hour and a half away). Anyway it ran a 14.56 @ 94.71 which I was pleased with considering the outside temp was 99*'s, and my radiator temp was near 200*. The second pass was a tad slower at 14.70 @ 94.56 because the jerk hosed down the burnout area so much I couldn't drive around it, so I had some tire spin. It's stock, minus the frisbee, w/de-screened MAF, and K&N filter w/open lid, so I thought it's not too shabby. Of course headers, duals, and whatever mufflers I can decide on are going on this winter. I may go for a 2500 or so stall convertor also, and hopefully a Dana 44 w/3.45's the following year. Thanks again to everyone who helped.

Rich K