aux. fan help

[hick92]

i know i read it here before but i can't seem to find it now but at what will make it turn on i think when the a/c is on but i don't remember

[Boots]

It should come on with the AC and when the engine reaches a certain temp. There should be a switch thing in the radiator.

[hick92]

ok thanks can someone please tell me where exactly this switch is located

[JeffN]

mine was drivers side on the radiator, there is a fan relay that will go bad also, it is on the drivers side fenderwell

[89er]

Is the fan running when the ac is on? See my aug 24th post and the info I got. I am still not sure that the aux fan is working off the switch as my truck never gets to the 230 mark, but replacing the ac relay on pass side fixed the running hot problem for me and fixed the ac. The relays in the system are all the same and about 10 bucks at auto parts store. I bought one and started at the radiator and exchanged it out till I found the bad one, so unless you have more than one bad relay you can run a test on system with just one. I found a wiring diagram in the dyi section under aux fan does not turn on. Good luck Ron

[ParadiseMJ]

mine was drivers side on the radiator, there is a fan relay that will go bad also, it is on the drivers side fenderwell

 

This is the aux. fan temp switch on a RENIX radiator

 

 

Some HO radiators come with the bung under a plastic plug, most don't. If it has a neck for the cap, it likely doesn't have the switch.

 

The temp. SWITCH runs thru the ECU and then the fan relay (on the DS fenderwell like JeffN said), the temp SENDER in the block for the gauge/light, the Coolant Temp SENSOR in the block under the manifold to ECU for fuel/air mix.

[mvusse]

On HO engines there's a temp sensor on the thermostat hosing that runs through the ECU.

 

Also some Renix 4.0s didn't have an auxiliary fan as my 87 doesn't even have the plug for one, or the relay for that matter.

[ParadiseMJ]

My 88 did not have a fan, but it does have A/C and the relay as well as the plug and wiring. It was easy to wire it to a switch. I converted the cooling system to a post 91 set-up, open, with a HO raidator. There was no bung for the RENIX switch.