View Full Version : Rad Fan electrical issue

banshee 101
08-29-2010, 06:00 PM
so i own a 91 celica gt4, recently my rad fan broke and my car overheated.
i replaced the fan with a derale and still had overheating issues. I now know that its an electrical issue, for the moment i just have the rad fan relay jumped so the fan stays on all the time.
so i know that when the fan switch is unplugged the fan should run all the time, which it doesnt, when i have it jumped of course i get power once i put the relay back in i get nothing, the relay clicks on but i loose power to the fan. i know that the rad and ac fans are grounded together and the power fluctuates depending on the temperature of the engine. so the ac fan still gets power. i've checked all grounds and wires and cant figure out whats causing the fan not to go on. i have check all fuses and relays, im kind of stuck

any ideas, i dont want to pass a new relay but im thinking it might be the best and less complicated option, i would like to keep everything as stock as possible, but we'll see, just wondering if anyone has any ideas

08-30-2010, 12:19 PM
I would advise to try another relay.

Just because your fan relay clicks doesn't mean it is working. The clicking noise indicates the solenoid (coil) part of the relay is working and is closing the contact. It doesn't mean the contact is in good shape and capable of allowing a lot of current flowing through it (pitted, burnt, or maybe just plain broke).

Try this first and let us know what happens.

banshee 101
08-30-2010, 01:39 PM
i forgot to mention that i did buy all new relays, installed them with the same outcome

08-30-2010, 02:09 PM
Hmm, something isn't right here.

You said you could hear the relay clicking. I'm assuming you are talking about the Fan No. 1 relay here, right? The one in the junction box located next to the battery?

If so, this tells me the coil side of the wiring to and from the relay is working fine. What pins in the relay connector are you jumping to get the radiator fan to run? Pins 3 & 4? Pin 4 is your power source, so if you are using that, then you have everything working on the power side of the radiator fan motor. So the only source of a no-run condition must be the relay. Interesting.

If you are not jumping pins 3 & 4, which pins are your jumping? If you are not jumping pins 3 & 4, check your 30A CDS fuse in the same junction box where your radiator fan relay no. 1 is located. That may be out.

banshee 101
08-30-2010, 05:32 PM
i am jumping 3 and 4, and yes fan n1, i had a very good electrical mechanic look at the issue and he got very frustrated because he could discover what was wrong, one thing to mention is when the fan died, its the actual fan blade that came loose and im pretty sure shorted the motor, when i took the fan off the blades were hardly attached to the motor. im thinkin git shorted something somewhere just cant find it.
all fuse were checked and working properly

08-31-2010, 02:37 AM
Do you have a 12VDC test light? It would be interesting, with the coolant temperature switch disconnected at the radiator, and the Fan No. 1 relay pulled, with the key on or the engine running, if you got the test light to come one when connecting across terminals 1 & 2 of the Fan No. 1 relay socket. If this test is positive (test light lights up) then the relay will close, and do exactly what your jumper between terminals 3 & 4 are doing. You said you heard the relay clicking, so one would assume you had a power flow between terminals 1 & 2, but why don't you check to make sure. And let us know what you find out.

banshee 101
08-31-2010, 05:36 PM
thats the thing i do have a test light, between 3-4 theirs power but 1-2 i get nothing, this is with the key on and the switch disconnected of course

08-31-2010, 11:08 PM
OK, how are you testing that you know you have power between terminals 3 & 4, but not between 1 & 2? Are you using a volt meter or a multimeter?

banshee 101
09-01-2010, 12:59 AM
multimeter, i had an actually mechanic test it

09-01-2010, 12:26 PM
Actually, in reviewing this circuit more, the results your mechanic got are correct, for a test that involved the coolant temperature switch being disconnected at the radiator.

The fan should turn on when this wiring harness at the coolant temperature switch is disconnected (or if the coolant temperature switch is reading a temperature above 93 deg C (199 deg F)), as it is a open circuit that activates the fans.

Are you sure you got the right relay in the Radiator Fan Relay No. 1? This relay, unlike most, is a normally closed relay (if no power between terminals 1 & 2, the contact between terminals 3 & 4 is closed). Pull your Radiator Fan Relay No. 1 out, and test that you have continuity between terminals 1 & 2 (coil side) and between terminals 3 & 4 (fan side, where the contact should be closed with no power flowing between terminals 1 & 2). If you do not get continuity between terminals 3 & 4, then either your relay is bad, or you are using the wrong relay part no. for this application.

banshee 101
09-03-2010, 01:15 PM
i've replace teh relay with a brand new oem which was tested before the install, the relay is good and its the right part number.

the fan does not turn on when i unplug the temp switch, nor does it turn on when the engine temp is over 93 deg. i do get power on the 3 - 4 terminals when the switch is unplugged, nothing from 1 and 2. when i plug the fan connector to the fan nothing happens, i have to jump terminals 3-4 to get the fan to start, which is how i have it set up for now.

let me know if that clears some stuff up

09-03-2010, 02:32 PM
Banshee101, we are trying to help you here, OK?

What is the part number for your Fan No. 1 relay? Mine is 90987-03001.

How was yours tested to ensure it is good? This relay is unusual in that it is a normally closed relay. When you have it removed and in your hand, terminals 1 & 2 do not have any signal power going through them. Yet, if you check continuity between terminals 3 & 4, you will have continuity (0 resistance) between these terminals, so the relay w/o power to terminals 1 & 2 will do exactly what your jumper is doing connecting terminals 3 & 4 now. So this is what is telling me that either your relay is not good, or it in not the correct part number (most relays are normally open, and they have the same pin pattern, which makes them look interchangeable, but they are not).

So let us all know what your relay part number is, and check if you have 0 resistance across terminals 3 & 4 of your relay when you have it disconnected from the relay block.

banshee 101
09-09-2010, 05:40 PM
resistance was checked and is okay, part number is that same as mentionned above
im just going to pass a new relay i guess, directly from the temperature switch

09-10-2010, 12:33 AM
Resistance across the coil part? What was it? Also, what was the resistance across the contact part when not energized?