Testing relays

[E150GT]

So I'm chasing down and ABS light in the Lexus. Its probably the pump but the codes say it's C1253 pump motor relay. I thought I'd check that first.
I read you can use a 9v battery across two terminals and it should click. Mine does. If I put my meter across the same pins for continuity it starts beeping after it clicks. Cool. If I leave the multimeter leads on it and remove the battery should there still be continuity across the two terminals ? As soon as I take a lead off one of the pins the beeping stops and I put it back it won't beep. I'm not sure if that's the way it should be or if the relay is bad.

 

[Nukeman7]

So I'm chasing down and ABS light in the Lexus. Its probably the pump but the codes say it's C1253 pump motor relay. I thought I'd check that first.
I read you can use a 9v battery across two terminals and it should click. Mine does. If I put my meter across the same pins for continuity it starts beeping after it clicks. Cool. If I leave the multimeter leads on it and remove the battery should there still be continuity across the two terminals ? As soon as I take a lead off one of the pins the beeping stops

Everything described above is normal.

and I put it back it won't beep. I'm not sure if that's the way it should be or if the relay is bad.

^^^^This behavior is abnormal, it should beep every time you apply power; however, you should only be testing with a 12 volt D.C. power source, not a 9 volt battery.

Can you swap that relay with another identical relay (from a different circuit) in the fuse box?

 

[E150GT]

Everything described above is normal.

^^^^This behavior is abnormal, it should beep every time you apply power; however, you should only be testing with a 12 volt D.C. power source, not a 9 volt battery.

Can you swap that relay with another identical relay (from a different circuit) in the fuse box?

Unfortunately not

 

[E150GT]

Sooo. While I don't have another identical relay I did pull another one that has 5 pins and did the same test. The continuity stops when the power source is removed as one would expect.

 

[Nukeman7]

So I'm chasing down and ABS light in the Lexus. Its probably the pump but the codes say it's C1253 pump motor relay. I thought I'd check that first.
I read you can use a 9v battery across two terminals and it should click. Mine does. If I put my meter across the same pins for continuity it starts beeping after it clicks.

You should be applying 12v power to terminals #85 & #86 to energize the relay. The audible meter probes should be attached to terminals #87 (not 87a) & #30 (i.e., the load circuit), not terminals #85 & #86 (i.e., the magnet switch circuit).

Sooo. While I don't have another identical relay I did pull another one that has 5 pins and did the same test. The continuity stops when the power source is removed as one would expect.

Per your description in Post #1, I don't think you have your meter connected to the correct terminals for the test. Take a look at the circuit diagrams for a typical 5 terminal Bosch relay here: What is a (Bosch) Relay?

 

[E150GT]

You should be applying 12v power to terminals #85 & #86 to energize the relay. The audible meter probes should be attached to terminals #87 (not 87a) & #30 (i.e., the load circuit), not terminals #85 & #86 (i.e., the magnet switch circuit).

Per your description in Post #1, I don't think you have your meter connected to the correct terminals for the test. Take a look at the circuit diagrams for a typical 5 terminal Bosch relay here: What is a (Bosch) Relay?

Very helpful. This is a denso relay and nothing is labeled. When I hook it up as described it seems to work properly.

 

[E150GT]

You should be applying 12v power to terminals #85 & #86 to energize the relay. The audible meter probes should be attached to terminals #87 (not 87a) & #30 (i.e., the load circuit), not terminals #85 & #86 (i.e., the magnet switch circuit).

Per your description in Post #1, I don't think you have your meter connected to the correct terminals for the test. Take a look at the circuit diagrams for a typical 5 terminal Bosch relay here: What is a (Bosch) Relay?

So if you test continuity between 85 and 86 they only should have continuity internally while energized ? I was getting readings where sometimes they would have continuity after power had been removed. That does not seem normal or maybe it is? It just not consistent.

 

[Nukeman7]

So if you test continuity between 85 and 86 they only should have continuity internally while energized ? I was getting readings where sometimes they would have continuity after power had been removed. That does not seem normal or maybe it is? It just not consistent.

Terminals 85 and 86 are the ends of the spiral wound magnetic coil (see below). Unless the coil is burned out, terminals 85 & 86 should always have continuity (although with some measurable resistance). Continuity between 85 & 86 does not rely on anything being energized.

Continuity between 87 and 30 should only have continuity when 85 & 86 are energized (i.e., when you hear the "click").

Your hookup looks correct if those alligator clips are the leads to the multimeter (see diagram below).

 

[Chris142]

How much is a new relay?

 

[E150GT]

How much is a new relay?

Shockingly $90 at the local toyota dealership

 

[f355spider]

How does one test this relay beyond continuity and ensure it can carry the necessary current/load?

I'd probably just throw a new relay at it and even if it doesn't fix the current issue, consider it "maintenance". Though you can open them up and examine the contacts.

I change out relays on some of my cars that have known issues for relays failing or sticking "on"...as maintenance. Not all of them, but the circuits with known problems. Usually radiator fan relays, or pump relays. Inspection can sometimes show some serious pitting of the contacts.

 

[nomas]

How does one test this relay and ensure it can carry the necessary current/load?

I'd probably just throw a new relay at it and even if it doesn't fix the current issue, consider it "maintenance". Though you can open them up and examine the contacts.

I change out relays on some of my cars that have known issues for relays failing or sticking "on"...as maintenance. Not all of them, but the circuits with known problems. Usually radiator fan relays, or pump relays.

All relays should have the coil voltage and contact rating marked on it somewhere .

 

[zzyzzx]

Shockingly $90 at the local toyota dealership

I would not spend extra money on an OE relay. It's just a relay. if you for some reason insist of getting an OE relay, try a junkyard.

 

[f355spider]

I would not spend extra money on an OE relay. It's just a relay. if you for some reason insist of getting an OE relay, try a junkyard.

Used electrical parts can be particularly risky due to storage conditions of the cars, often open to the elements in junkyards

 

[f355spider]

All relays should have the coil voltage and contact rating marked on it somewhere .

But is there a way to test for that, short of complicated or expensive testing equipment?

 

[X15]

How does one test this relay beyond continuity and ensure it can carry the necessary current/load?

I'd probably just throw a new relay at it and even if it doesn't fix the current issue, consider it "maintenance". Though you can open them up and examine the contacts.

I change out relays on some of my cars that have known issues for relays failing or sticking "on"...as maintenance. Not all of them, but the circuits with known problems. Usually radiator fan relays, or pump relays. Inspection can sometimes show some serious pitting of the contacts.

You can measure the contact resistance, but it's still somewhat of a judgement call. You have to do it with the representative or actual load the contacts are switching though, just using a DMM on resistance won't cut it.

https://www.te.com/en/products/rela...ation-diagnosis-suspected-relay-failures.html

 

[Randol]

Wow, If I read the original post correctly you are using your continuity beeper across the coil, while you are powering the same coil with a 9V battery? Don't do that.
DMM's have different thresholds of resistance for when they will beep and you don't use an ohmmeter or continuity beeper on powered circuits, you get weird results connecting two sources.
Check the coil using the DMM in the ohms setting, Slightly tap the relay while connected to see if the resistance jumps around, an analog meter comes in handy here. The #1 failure mode are broken wires inside that can be intermittent.
You have established the relay clicks with 9V applied. Tap it while energized to see if it drops out.
Some relays have built in flyback diodes, so they can be polarized.
Next check the contacts. As X15 said, it's best to connect a representative load. If the contacts switch an arcing load, a DMM may show the contacts as open. Check all poles and both NO and NC contacts. Try tapping the relay too.
I'm not sure if you are dealing with the generic automotive 12V relay here or not, it looks smaller to me.

Check your wiring to the relay as well.
Have you checked the Lexus forums for similar issues, those guys can be pretty helpful.

Hope this helps.