1988GTA500HP

My son's 88 GTA has had a TPI to carb swap and has a single coolant fan (I believe stock is dual?) which is wired to come on as soon as you turn the key. I think the car is taking too long to warm up and I would like to fix it so that the fan comes on when needed.

Pic 1 shows the coolant fan, which has 2 wires (dark blue and gray).

Pic 2 shows the fan relay (1 of 2 I believe, I assume the other one is not being used but I haven't traced the wires yet). I traced the wires back from the fan and the gray wire is grounded to the fender well. The blue wire is spliced into an orange wire which is then spliced into the white wire that fed the relay originally. It's hard to tell in the pic but you can see the exposed copper wire from the relay which is white.

Pic 3 shows what I believe is a plug in the vortec head.

From using the search function and hours of reading threads, I think I know what needs to be done but would like to confirm it. I believe I have to:

1. Disconnect the white wire from the fans blue wire and reconnect it to its original position on the relay.

2. Cut into the orange wire on the relay and attach the fan blue wire to the orange wire coming from the relay.

3. Remove the plug from the Vortec head and install a thermal switch in its place.

4. Connect the thermal switch to the dark green/white wire coming from the relay.

If I am correct, any idea what temp the thermal switch for the head needs to be and do I need to drain the coolant before pulling the plug? Any help at all is appreciated.

Jeffs82TA

iTrader: (1)

the orange wire goes to battery/fused power
red goes to an ignition source
green to thermal ground switch
black/red to fan motor

then you ground the other fan motor wire.

1988GTA500HP

It doesn't have a red wire. It has a white wire which has been cut and fed to the fan instead of to the relay. The fan comes on when I turn the key so the white wire must be an ignition source. The green wire has a white stripe. So if I understand you correctly, I should hook the white wire back up, run the green/white wire to the thermal switch, BUT hook the black/red wire to the fan, not the orange wire?

Jeffs82TA

iTrader: (1)

yes the black/red wire is the postive fan motor wire.

Orange will be to battery source and fused

then maybe white was ignition source, I just though it was red is all.

the extra wire of the fan motor just ground to frame or something.

1988GTA500HP

Thanks Jeffs82ta, you're aces in my book.

Anyone have an idea on the thermal switch I need?

1988GTA500HP

I don't know if this is the temperature guage sender/switch or what I need for the fan relay. Anyone?

http://www.autozone.com/autozone/cat...&parentId=52-0

Jeffs82TA

iTrader: (1)

just buy a 87-92 GM sensor they generally are 228on 204off

Jeffs82TA

iTrader: (1)

http://www.autozone.com/autozone/cat...&parentId=63-0

1988GTA500HP

Wow. Thanks again Jeff, I really appreciate it. I'm off to autozone tomorrow.

1988GTA500HP

Jeff, or anybody actually, would you happen to know which head, drivers or passengers, toward front or back, the coolant fan thermal ground switch was mounted in? I am trying to see if the original connector is still attached and dangling somewhere, but haven't had much luck. I may be digging in the wrong area though. Thanks.

Jeffs82TA

iTrader: (1)

passenger side between 6 & 8th spark plug.

1988GTA500HP

Thanks again Jeff...my heads have a plug in exactly that spot. May have to go to the JY for the connector though.

Jeffs82TA

iTrader: (1)

autozone usually carries those connectors or napa. If you can't find a good one at J/Y the knock sensor is the same connector as well.

Pocket

iTrader: (24)

Its the same as a knock sensor so you shouldnt have trouble finding one from any common GM car

The circuit you described in the first post seems sound and should work

A side note, the fan only cools the fluid in the radiator. When the engine is warming up, the t-stat is closed and fluid is not circulating back to the radiator so the fan is cooling already cool fluid. Once the t-stat pops it will circulate and cool like normal, but until it does the engine is closed off indifferent to what happens in the radiator and how cold it is. For a slow warm up condition, Id check for low coolant or sticky t-stat instead of over cooling from the fan

That being said, running the fan continuous from the IGN is a good way to burn up the fan and lead to a disaster down the road. An automated fan switch like you're doing is recommended regardless of what actually is causing the slow warm up

1988GTA500HP

Okay, now I'm a little confused. Do I attach the orange wire or black/red wire to the fan or will it work either way?

Great news they carry that connector at parts stores. I never would have thought that unless GM continues to use that connector today. The car is 22 years old.

And thanks for the info, Pocket. I knew the coolant didn't circulate until the thermostat opened but I thought that maybe the fan was cooling the block a little just by running.

Jeffs82TA

iTrader: (1)

1988GTA500HP

Oh thanks, Jeff. That is very helpful. I printed it out.

Of course, I don't have the ECM anymore so I hope it all still works.

Jeffs82TA

iTrader: (1)

Don't worry about the wires going to the ecm. In your case just run that green/white wire to your thermal sensor.

1988GTA500HP

'preciate it, Jeff...I'll let you know if it works.

1988GTA500HP

Jeff, you were right. It didn't work at first and after much troubleshooting with my test meter, turns out the new thermal switch was bad. I got another one and it works perfectly. The car is def running hotter now and it actually feels a little smoother. I think it was running too cool. After all the troubleshooting I am starting to figure out how these relays work.

The D terminal (white) is the input to the relay controlling circuit and gets power when the key is in the run position.The F terminal (green/white) is the ground from the relay that completes the controlling circuit. However, since it is fed to the thermal switch the circuit isn't completed until the thermal switch reaches a specific temperature and then grounds itself to the engine block.

The E terminal (orange) has a constant 12 volts and is the input to the fan circuit. It's normal position it's connected to the C terminal which is unused. When the thermal switch grounds itself that causes the E terminal to switch to the A Terminal (black/pink) so power is fed to the fan which is grounded straight to the body and the fan turns on. When the thermal switch cools off enough it removes the ground from the block which causes the E terminal to switch back to the C terminal killing the power to the fan.

Thanks so much for all your help. This is much better than having the fan always on.

Jeffs82TA

iTrader: (1)

Make sure you don't use thread sealer on coolant related sensors since this can cause a grounding issue. I've never had one leak without sealer on them.

Jeffs82TA

iTrader: (1)

If you want a toggle switch control in case the thermal switch fails. Just ground one terminal on the switch and run wire from the other terminal to that green/white wire and you can manually turn the fan on at anytime.

1988GTA500HP

The thermal switch came with teflon tape on half the threads. I was worried about that. I may take it out and pull the tape off. I wondered if that is why the first one wasn't working. The guy at napa said they always do it that way.

Pocket

iTrader: (24)

Teflon is to make a water tight seal between the sensor and head. As long as its not wrapped so thick it cant thread into the head, you wont have an issue

Remove it and you risk a slow drip

SERIO

Hey jeff I been searching for this all over the threads lol. So what you are saying the ground on the switch that I bought will connect to the green/white wire going to my thermal switch right. Then after that I can flip my switch to turn on my fan or let the thermal switch do it right. Hope that's what you meant.

1988GTA500HP

Hey Serio. Yeah the thermal switch in the head is simply a switch that goes to ground. It switches itself at specific temeperatures. Adding your own switch to ground will override the thermal. If you want to keep the thermal switch too then you will just need to add an alternate root to ground. Splice into the green/white wire to feed your switch, so it will be like a "y". The other connection on the switch should go to ground. You want to keep the wire going to the thermal switch as well which will function normally when your switch is off.

Weffy

What is that schematic from?

SERIO

Oh ok cool. Thanks a bunch. Summer is gonna be more fun now lol.