Measuring Continuity....??? Options

[FrankB2]

Okay.... I recently tested a relay for continuity, and two terminals caused my meter to beep, and the other two terminals caused my meter to read .064 without beeping. I came across a car forum question, in which the poster was using a 4 pin toyota relay on his hot rod, and was testing continuity. This was the same normally closed relay I was testing, and he got the same results. One person said the .064 was continuity for Toyota relays. I'm not an electronics wizard, so if anyone has any knowledge here, that'd be great. I broke a relay case yesterday tugging it out, and picked up a new relay this morning. It's supposed to have continuity across two pins and no continuity across the other two (fan relay no. 2) without power. Both the new and old relay read .061 ohms across the pins that are supposed to have continuity, so I'm guessing that's continuity without the beep.

[Special_Edy]

Just swap the relay with your starter or efi relay. If the problem follows the relay and the efi or starter act up you have a faulty relay

[FrankB2]

Hi Edy,
I saw your post with this advice (Thanks!), but I was curious about continuity testing these relays. My son did say something about it yesterday, but he mumbles... and he left for his base again. He works on C5 aircraft, and the avionics are self diagnostic now. He just pulls and replaces components. Lockheed Martin has civilian workers on base, and they encourage the LOTS of replacement parts.....$$$$$$

[Special_Edy]

Okay so terminal 86 is the input, terminals 85 is ground and these are most likely a wound coil that act like a magnet to throw a small mechanical switch inside the relay. The mechanical switch bridges 30 (which is 12+ from the battery) and terminal 87(the output to the accessory) so power can flow to the component of the car being powered by the relay.

So 87 - 30 should have no continuity and 85 - 86 should have continuity. How much, I dont know. But there should be some resistance present.


I wonder, if the relay is stuck ON then wouldnt the fans run even with the ignition shut off? I think the relays are wired straight to the battery not through the ignition.

Try turning the car on so that the fans begin running, then pull the relay out and test for 12v across terminals 85 and 86 in the socket of the fuse/relay box. If 12v is present then the ECU is erroneously telling the fans to run, if 12v is not present then the relay is likely the culprit

[FrankB2]

Hi Edy,
With the engine ice cold, I followed your procedure. Engine off key on, the fans were running. Pulled the relay, and they continued running. Tested 85 and 86, no voltage. This is a normally closed relay, and when I tested it with power off the car, the switch did open (no continuity between 37 and 80). The EFI is buried deeper than the Fan relay, and I stopped after giving it a tug. It's like Toyota doesn't want to make removing relays easy.... or I need a tool to pull relays. I did order another fan relay from the dealer, but that's going to cost $85 to test. Junkyards are nonexistent where I live.

I did test the resistance of the ECT sensor. Yesterday was in the 70's, and a cold reading was 1.92 kOhms. This morning was 57 degrees, and I got 3.2 kOhms. Seems like a big difference for less than 20 degrees ambient temperature. The harness is sending 5 volts, so....? I measured the sensor last week, and the resistance dropped considerably once the engine warmed.

P.S. I looked for any signs of the fans being wired to the ignition, but couldn't find anything. It looks 100% factory.

This post has been edited by FrankB2: Sep 14, 2013 - 9:21 AM

[FrankB2]

Thinking...... this is a normally closed relay, and when energized, the switch opens breaking continuity between 87 and 30. Shouldn't I be getting 12 volts to the relay when the engine is cold? It would seem that 12 volts at the relay when cold would open the circuit, and cause the fans not to run. That doesn't account for the fans running without a relay at all, however.

[Bitter]

Usually when I see a toyota with the fans on all the time it's a bad temp sensor/temp switch. I'm not sure how the Celica is wire up but other toyota have a redundancy in the system which causes the fans to run high speed all the time when a part of the circuit fails which is why the relay is normally closed, it's opened by an input from the operational circuit and closed when a failure occurs.

[Special_Edy]

No the relays are naturally open circuited, with no continuity at all

When power is applied across 85 and 86 the relay closes and sends power.

This way, the relays always have direct power from the battery (30) and only come on when the ecu sends a 12v signal to terminal 86



If the fans are still running when you pull out the fan relay there are 2 possibilities I can think of-
-You are pulling the wrong relay, my 94 GT has 3 fan relays, two in a small relay box near the top passengerside of the radiator and just behind the highbeam (the radiator fans I think) or a single relay in the main fuse/relay box along the driverside fender(this is for the climate control blower motor)
- Or you have a direct short circuit between the radiator fans and some ignition wire.

[FrankB2]

Hi Edy,
I'm using this BGB schematic: http://bgbonline.celicatech.com/94_6gmanua...0four%20cyl.pdf
It's for a 1994, but I'm guessing it applies to my '97. Fan relay no. 1 is supposed to have continuity across the pins shown on page 3, without power. With power, pins 30 and 87 loose continuity. The relay I'm pulling is the green topped one closest to the driver, on the outboard side of the engine compartment fuse panel. I thought about putting a paperclip in the slots for 30 and 87 to see if that would shut the fans off when the engine is cold, but I'm not that desperate or crazy yet.

Edit: according to the BGB above, the engine main relay is supposed to be tested as well.

This post has been edited by FrankB2: Sep 14, 2013 - 12:57 PM

[FrankB2]

Went to Toyota, and niece's boyfriend used a scan tool that read coolant sensor. Bought one, and have to wait for the temp to drop. We did check the volts at fan relay no. 1, and with the engine warm, it was getting 11.8v. Hopefully this will be the end of my fan nonsense, and I can move on to getting the front bumper cover painted.

Edit: Installed ECT Sensor, fans still running when engine is cold.......

This post has been edited by FrankB2: Sep 15, 2013 - 7:48 AM

[Bitter]

1997 GT Convertible diagram. 3 switches that feed ground to the various relays, it's a somewhat complicated system at first glance but once you trace it all down and look at it as a BASIC AND/OR sort of operation it's not so bad.

[FrankB2]

Excellent! From the looks of that schematic, the radio I installed last October wouldn't be an issue. I haven't done any other electrical work to the car, so I guess it's a matter of testing all the relays shown....and then look at the ECM.

[Bitter]

I'd look at the thermo switches and pressure switch first. Much more likely that one of those has failed.