Hi. I'm new on this forum but not new to F-bodies or Corvettes. I just bought a 92 Z28 5.0L TPI, auto, (dual fans). As with ALL of these cars, they all run way too hot in stop and go traffic and idling. I've slapped in the usual remedy in all my other cars: hypertech thermomaster, 180 t-stat, and fan switch on @ 200/ off @ 185. This always seemed to work, but before I drop the cash...I want to know if I can just get away with putting in the 200/185 fan switch. Obviously theres no problem with air flowing through the radiator. This post may even seem redundant but I've read page after page on here and the opinions are all over the place and what I'm looking to do doesn't appear to be discussed. I don't want to screw up closed loop operation and yes I like having heat. I know everyone on here hates hypertech and honestly I didn't buy it for prior vehicles for any performance gains (never noticed a thing)-I just want my car to run no hotter that 220 no matter what the conditions. All input appreciated. Thanks =)

 

I run a 180° thermostat and the fan switch you mentioned. Car runs around 180° – 190°.

There's a lot of mis-information on Closed Loop. The fan switch won't have an affect on Closed Loop operation.

Closed Loop kicks in much sooner than most people think. Basically, the ECM looks at 3 things — how long the engine has been running, if the O2 Sensor is warmed up enough, and coolant temp.

The ECM goes into Closed Loop at — something like 2 min. run time from cold start, varying voltage from the O2 sensor and coolant sensor reading around 104°. It doesn't take much to meet these criteria. Definitely long before a lower t-stat or fan switch will have any affect.

Hope this helps.

 

Thanks for the info. It's good to know that I don't have to waste $ on the chip when all I'm looking for is a remedy to the car running too hot.

 

Just remember, that fan switch controls the secondary fan, the primary fan is controlled by the computer. It is normally set at 226*(108 celsius). You have to reburn the chip to change that.

 

Who would be best to contact to do the re-burn...also without putting my z28 in a "car-down" state for an excessive amount of time. Thanks

 

Interesting thing I've noticed is that on my car, both fans always turn on and off together. Makes my wonder that if the ECM seems the second fan turn on, then it goes ahead and turns on the primary fan.

 

You may wish to read the cooling fan article in the tech section. I found it to be very helpful.

Here are my suggestions.

1) Install the fan switch in the head which controls the secondary (usually left) fan. Then wire the fan relays together so that both fans operate with the in-head switch. This eliminates the problem with the computer controlled fan not turning on til 226' (or whatever the computer is programmed) They will both work together. Note that the primary fan won't come on when the A/C is turned on but I've found that the temperature is such that the fan is on anyway.

or

2) Re-program the computer to turn on/off where you desire and wire the relays together so that both fans operate together. Same benefits as above and they will still operate when the A/C is turned on. Also you won't have to buy the in-head switch.

or

3) Purchase a universal fan control relay like the Hayden one's sold at Autozone, Advance etc. Then wire both relays to the Hayden unit. The benefit here is that the fan control is adjustable so you can fine tune the on/off points.

I currently have option #3 installed on my car with an auxillary pusher fan in the front. All three fans come on together and it works really well. For the first time since I've owned this car the fans acutally turn off! Also, I am about to be able to reprogram my own chips and will convert to option #2 at that time.

I have used the 160' and 180' tstats with preferance given to the 180'. I am planning to use a 170' tstat GM # 10220957 on my next change.

Hope this helps you out.

 

Contact Angel at TPI Parts: www.tpiparts.net

He programs "piggyback" chips that make minor program changes to the stock PROM, one change being the fan temps. Here's the specific page:

http://tpiparts.net/inc/sdetail/657

The price is about 1/3-to-1/2 the price of buying an aftermarket chip. And the only downtime is the time it takes you to plug it in because you don't have to remove your chip until the new one arrives.

 

My solution is simple and works great for summer and winter.

180° thermostat
PCM programmed for on at 190°/off at 185°
fan switch 200°/185°

On a mild day, the car will run at 180 with the fans off. Go up a hill or get on it, the first fan might turn on. Occasionally the second one will too. Hot day and both fans keep the car in the 180°-200° range.

Of course on a hot day, the A/C kicks both fans on anyways regardless of PCM or fan switch settings. But it's still nice to have it run cool when you have the A/C off.

With the above setup, I have no worries about burning out fan motors from overuse.

 

I have a 92 Trans Am LB9 5spd, primary fan only comes on when A/C is turned on, has nothing to do with temp, just A/C pressure.

 

Thanks a lot for the responses =)
I think I'm going to contact the tpi parts website and have the piggyback prom programmed. Does fans on at 205 and off at 185 sound good. I think I'll put a 180 t-stat in it as well. So if I have this done, I shouldn't have to bother with the fan switch in the passenger cyl. head right?
The talk about wiring the relays together is really interesting. How would I go about doing that so both fans come on? I don't have wiring diagrams. Anyone got pics???

 

Super easy- well at least straight forward. On my 89 IROC the main fan relay (passenger side) is mounted on the fender just behind the battery and the secondary fan relay (drivers side) is mounted just under the radiator cap beside the battery. If you pull the connector from the relay(s) you'll find the "signal" wire. This is the ground wire that controls the relay. It's the green wire with a white stripe, 18 ga I believe.
Now what I did is to cut each of these wires about 2" below the connector. This gives you enough wire to work with. If you want both fans to work off the computer, then connect both wires that are still attached to the connectors to the green wire in the harness that used to be connected to the primary fan relay. If you want both fans to work off the fans switch in the head, then connect both wires that are still attached to the connectors to the green wire that used to be connected to the secondary fan relay.
Or (and this is how I currently have mine hooked up) install a Hayden fan control relay (available at Autozone) to both fan relays and totally bypass the factory controls. The advantage to this method is the Hayden fan control is adjustable. You can change the settings by simply turnig a **** under the hood. When I have the ability to burn my own chips I may elect to return control to the computer.

 

That's great advise. I think I'll try this before going the the prom route. So if I walk into an autozone looking for this Hayden relay, will they know what I'm talking about....any part #'s and rough idea on price? Thanks a lot =)

 

Mine's mounted and I can't see the part number. It came in an electric fan kit, but it's sold separatly. It's about 1 1/2" wide, 2" tall and 1" thick. It has a adjustment post (like you'd put a **** on) sticking out the front. It has a tiny (1/16" od) capilary tube about 18" long with a bulb on the end about the size and half as long as a pencil. I've seen them out in the isles by the electric fans and accessories.

This is a mechanical relay. That is the bulb is heated by the radiator and "mechanically" shifts the relay. I hooked one terminal of the relay to ground and the other to the stock electric fan relays. When the auxillary relay senses the temperature go up it shifts and turns on the factory relays therefore turning on the fans. Works pretty slick.

BTW- The "bulb" is supposed to go in the radiator fins against the cross flow tubes. It worked fine there but I moved mine directly in the upper radiator hose. Just bend the capilary tube so it follows the radiator inlet and then makes a U-turn so the end of the bulb is pointing twards the front of the car but inside the upper hose connection. I smeared a little silicone around the capiary tube and slid the hose over it and clamped it down. Hasn't leaked a bit.

 

sorry if this is a bit off topic, but i see everyone posting about primary and seoncdary fans, i only have a single fan, is the procedure still the same?

 

Here is a good site for wiring on our cars:
http://www.autozone.com/az/cds/en_us...rInfoPages.htm