Hello I have a 1999 aura tl. Car runs normal no check engine light. When car reaches normal operating temperature the fans should cycle on and off normally. My fans won't kick on until gauge reaches 3/4 the way. Now to help keep my engine cool I run a/c on all the time because the ac switch turns on my fan and it helps disperse the heat. My guess is coolant switches. Only problem is there are two switches on the schematic and I can only locate one switch on the engine the other very hard to find. Any educated ideas?

 

The second one is behind the timing belt cover near the water pump... yeah it sounds that fun to replace.

 

Now the one by the water pump is that the sensor I need to change? To my understanding one turns on around 180 degrees and the other around 220. The one switch for 220 (almost overheating at 3/4) works but the one switch that should kick on at normal operating temperature is not kicking on my fans. Which one is which? The obvious temp sensor I found is near the egr not sure which one to change

 

Its called "Fan Switch" and yes they are 2 in the Base Model, Type-S has 3 of them.
Both models share the same locations, Water Pump and Lower intake manifold near the EGR. Right at the A/F intake tube is the temp sensor for the gauge.

What I can tell you is that the Temp sensor can go bad and it will trigger bad temp readings.. What makes you think the Fan Switches are bad? A notorious case of overheating will make the A/F reservoir overflow.. If your reservoir is at normal levels then the temp sensor must be going bad...

Mine failed at 190K it showed full overheat for 2 seconds then dropped back to normal levels then rise again continuously..

 

I think one of the switches are bad. These acuras normal running the gauge stays below halfway, if I don't turn on the ac, the fans wont kick on until 3/4 meaning one fan switch isnt sensing the car reached operating temp and sending signal to the fan to cycle on. The million dollar question I have the base model, which fan switch do I change? The one by the water pump or the one under the intake?

 

Do you have the Service Manual? there is troubleshooting for the switches using a volt-meter.
In any case you don´t want to mess with the one near the timing belt... its a whole day job just to get to it, replace the easy one first?

What I find curious is why you dont get a MIL Code.. The switches have their own MIL codes for each one.

 

The temp gauge isn't sporadic it rises and drops normally like it should gradually.

 

Unfortunately I don't have the service manual. If I did it would tell me which sensor turns fans on at operating temperature and which sensor turns fans on at 3/4 before you blow your gasket and crack your engine

 

3/4ths wont damage the engine.. Its full overheat which will do.
Let me find the pages and I will scan them for ya.

 

Thanks, where can you buy a service manual with such in depth diagnostic troubleshooting?

 

You can download it, The links should be up in the Service Manual Thread here in Acurazine. If they aren't I can upload it for you but it will take me a while since its 680MB and my Upload speed is garbage.


Here are the pages about it:



Fan Switch A



Fan Switch B



* Don't mind the Fan Switch C as its only for the Type-S

 

Awesome man thank you so much

 

It appears im in luck as per the diagram switch a is bad. The one that's easy to change. I'll change it, burp system and I'll update if It's fixed

 

Fan Switch A is the usual cause, iirc 99 its on the thermostat housing?? easy on top of engine access
Follow owner book on burping- its much more than let it run at idle~
Make sure the heater is set to full hot temp and cabin fan is on full speed when burping
Open car doors to allow hot air to escape
Mini radiator that is the heater loves to hide air!

 

Yea it's easy to change but I still have the same problem. Gauge goes 3/4 and switch b overrides and turns fans on. I even jumped switch a at thermostat housing and fans kick on. I changed the sensor twice same issue. Now what? Everything seems to be fine. I wonder if there is a switch stuck in fan control module? Do you have any ideas?

 

Actually now that I think about it. If the thermostat is bad and opening and closing incorrectly, it will greatly affect temperature and what a coincidence the switch that's not sending power to fans is sitting exactly on THERMOSTAT HOUSING. I think it's time to change thermostat, it's ten bucks plus 3 for a gasket, what do I have to lose at this point

 

Try it out and see how it goes. I had an overheating issue in the 2G a few months ago but it was the relay box under the hood itself that went bad.

 

Awesome news! It's fixed after replacing thermostat. The old thermostat was not opening enough to submerge the coolant sensor on the thermostat housing therefore ultimately not turning on my fans causing slight overheat. It's crazy but 100% true. My needle stays below halfway at all times it was hot here in Pennsylvania today all good. It's crazy because I changed sensor thinking that was issue but a stuck thermostat. The old one was torn and ripped, no more driving with heat on blast to keep gauge down! Thanks guys for helping me pinpoint my issue! This one solved.

 

Glad to hear you're all set. This forum has helped me out a lot also.