Fan always on
Thread Starter
6th Gear
Joined: Oct 2018
Posts: 6
Likes: 0
From: Ashland, Ma
Fan always on
So problem was noticed when AC was turned on, light blinks a few times then shuts off, no AC. Then noticed the fans always running, fans stop when I shut the car off. Car seems to be running good otherwise it's a 2002
Any thoughts are appreciated
Andy
Any thoughts are appreciated
Andy
Drifting
Joined: Jul 2015
Posts: 1,844
Likes: 375
From: San Jose, CA
Those are two separate problems. Your AC doesn't work, and your fans always run.
Are you sure your fans always run? You turn the car on cold, coolant temp is 80F ... are the fans on? We can diagnose along with you, but you need to verify some stuff first.
Anyways, to fix the AC, I generally recommend you bring it to a shop. I know, I know. I try to DIY what I can, but I've learned that AC stuff is just really annoying. Chances are you are low or empty on refrigerant. Chances are that's because there's a significant leak in the system. You could figure out where that leak is, but a shop will probably do it faster. You can fix it, but AC systems are a pain and shops work on that all the time. And the shop will also do it in a way that's much better for both the environment and health (read: your health: because if you fix it yourself, you're gonna breathe in r134a, which is not nice.) To diagnose and repair the AC yourself you generally need manifold gauges and probably a vacuum pump, along with some adapters, UV-dye r134a cans, and potentially AC oil (I forget the precise details of which.)
Are you sure your fans always run? You turn the car on cold, coolant temp is 80F ... are the fans on? We can diagnose along with you, but you need to verify some stuff first.
Anyways, to fix the AC, I generally recommend you bring it to a shop. I know, I know. I try to DIY what I can, but I've learned that AC stuff is just really annoying. Chances are you are low or empty on refrigerant. Chances are that's because there's a significant leak in the system. You could figure out where that leak is, but a shop will probably do it faster. You can fix it, but AC systems are a pain and shops work on that all the time. And the shop will also do it in a way that's much better for both the environment and health (read: your health: because if you fix it yourself, you're gonna breathe in r134a, which is not nice.) To diagnose and repair the AC yourself you generally need manifold gauges and probably a vacuum pump, along with some adapters, UV-dye r134a cans, and potentially AC oil (I forget the precise details of which.)
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,626
Likes: 4,069
From: Cape Coral, Florida
WAAAAY to early to look at those crazy fan wiring schematics but it sounds like "maybe" the control relay driver (C1 connector pin 33- dark blue wire) at the PCM may be "stuck" closed...it provides grounds to both Fan 2 and 3 relays....I'd pull both cooling fan relays #2 and 3 and with a test light connected to battery POSITIVE when you turn the key ON see if the test lights illuminates when probing pins 85 at both relays...just look underneath the relay and you see how they are numbered...if light works with key ON the driver is stuck on...just thinking of some inputs that may be turning on the driver...say like a bad coolant temp sensor...just a guess !!...maybe I'll test out my new "sensor simulator" and crank in some "coolant temp" and see if the fan turns on !!
EDIT: when the fan is running yank the connector on the ECT sensor which sits by the #1 spark plug wire and see if the fan stops...sometimes the computer uses what we call "substituted values"...it what the computer "thinks" the value (temp) should be...you have to use a scan tool on the "OBD2 Generic" and not on the "Enhanced or Factory" side to see what the REAL ECT temp is !!
EDIT: when the fan is running yank the connector on the ECT sensor which sits by the #1 spark plug wire and see if the fan stops...sometimes the computer uses what we call "substituted values"...it what the computer "thinks" the value (temp) should be...you have to use a scan tool on the "OBD2 Generic" and not on the "Enhanced or Factory" side to see what the REAL ECT temp is !!
Last edited by C5 Diag; Jun 4, 2019 at 10:26 AM.
Drifting
Joined: Mar 2013
Posts: 1,496
Likes: 355
From: Little Rock Arkansas
Blinking light on the HVAC panel typically means system is low on Freon. You can actually check these things on the DIC as A/C levels will through a stored DTC code. Another issue that will cause the A/C button to blink is if outside ambient temperature is too low. If the OAT sensor detects a low temperature (it's something like 35 F) it will not allow the A/C to come on. This can be very easy to have happen if you say store your car in climate controlled garage and start it early in the morning (I don't know how cold summer mornings are in MA this time of the year).
The fans work a different way depending on the speed. On low setting the fans work in a series cutting the power delivered in half (for each). On high the relays shift to parallel power. Before digging in too deep I would check the relays.
A Tech 2 device will be able to tell you more since it can read what speeds are being operated at what time & what temp. It's sometimes difficult to tell what exactly is going on just by listening or trying to look at the shroud.
The fans work a different way depending on the speed. On low setting the fans work in a series cutting the power delivered in half (for each). On high the relays shift to parallel power. Before digging in too deep I would check the relays.
A Tech 2 device will be able to tell you more since it can read what speeds are being operated at what time & what temp. It's sometimes difficult to tell what exactly is going on just by listening or trying to look at the shroud.
