Trying to learn about relays

Hi, I’m new to the site. I need help trying to learn about relays. I have real bad dyslexia all my life and very hard to learn something. Even writing this I will leave out few words and spelling, spell checker has melt down trying to figure what I’m trying to spell, that just a small part of my dyslexia.

So here it goes. On this site I have readied the stuff about relays and on how to test them using the numbers on the bottom of the relay, like 30 with 87. My car relays have no numbers on the bottoms.

I have a 2003 Pontica Vibe 1.8 all wheel drive, 175.000 miles on it. The a/c was acting up, when the car was cold the a/c would work, but the car got hot from driving and shut off the car and start it up after 15 minutes the a/c would not work. You hear the rpms go up and fan comes when you push the a/c button on, but no clutch spinning, I check the allen nut on the clutch face and it is tight. This went on for a week. Now when you press the a/c button nothings works. No higher rpms, fan doesn’t turn on, and no clutch spinning, when the car is cold.

What I have readied on this site that relays can get hot and cause problems, and I’m pretty sure it a relay problem.

The fan does come on for water temperature. I have a test meter, with cheat sheets.

Relays.

FAN No.1, Toyota Denso, 90084-98031 TN 156700-1027 12v on the back 8.D-20 4 prong

FAN No. 2, Toyota Denso, 90084-98032 TN 156700- 1062 12v on the back 9.D-5 5 prong

M/G CLT, Toyota Denso, 90987-02022 15600-2470 12v 4 prong

None of these have numbers by the prongs.

How can I test the relays.

How can I check for power to a/c clutch.

How can I hot wire with the relays out to see if the clutch come on and if the fan come on and rpms go up.

I need the a/c to work, I have a bad heart and it hot and humid, I have no money to have it check out and fix. Any help will be great.

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Run a DMM set to ohms to any pair of terminals.
The pair that differ by about 100 to 500 ohms are your coil terminals.
You can run 12 volts across these and then with 4 terminal relays, the third and fourth are joined/switched/commoned. With 5 terminals two out of the three others will be commoned, when 12 volts is applied across the coils that common join switches over.
Cooling fans should come on as soon as AC is switched on irrespective of ambient temperature.
AC compressor, test for 12 volt at the lead or apply 12 volts to that lead to see or hear if the clutch switches in. Have you tested battery, alternator and cooling system? First things I would look at. It's a bloody Toyota, I wouldn't suspect the electrics at all. Has there been any crash damage to the front, also have you checked the fuses properly?

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks for your help. The battery test was good, only 6 months old. Alternator check fine. When this first started with a/c, I took it to garage and the freon was tested fine and no leaks. But the car was hot and they said there was no power to the clutch and wanted $550 to fix it. Can’t afford it but the next day when the car was cold the ac work find, and that went on for over a week. When the car was hot only the fan would turn on and rpms went up and no clutch, but I lost that now even when the car is cold now. The fan will come on when the water temperature get hot.

I check all the fuses twice and replace them anyway, and there was no crash damage to the car ever.

Thanks for your help, will try your suggests.

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Try the other tests I mentioned but I'm thinking faulty compressor.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

So now when you turn the AC on from the control head you don't get the A/C or HighSpeed fan or engine RPM increase regardless of engine temperature?

The compressor won't engage if you are low on refrigerant, but you mentioned that has been checked.

Do you have an electronic heater control or is it a manual style control? (Knobs and dials or digital) Wonder if the AC request isn't making it out of the control head.

Yes, my second thought was refrigerant R132 not what the poster said, try running the wire from the compressor to your battery pos, we can then know if it's actually the compressor, you will hear the clutch clicking in.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks for the help. My wife is very sick and I haven’t had a chance to try your suggests yet, I will try tomorrow.

So now when you turn the AC on from the control head you don't get the A/C or HighSpeed fan or engine RPM increase regardless of engine temperature? That’s correct.

I have manul control knob and turn to the coldness setting.

Thank-you very much for your help. I will let you know what happens.

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There was only one black & white wire running to top of the compressor to a connecter that I can’t reach. Is this power or ground. Is there away to jump the compressor in the junction box.

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It will be power, every compressor I've ever seen was grounded through it's casing via the bolts to its mounting on the engine block, thus that's a power lead not a ground, Using a Stanley knife, bare some of the cable.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks,  I will check it out and test it.

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I have a digital multipmeter. I expose copper wire on the black & white wire going to the compressor. I check my ground to the battery pos side and it was good, there was no power going to the compressor. I check the fuses under the dash again and they were still good.

I then pull RDI Fan fuse 40A from the junction box and continuity was good.

I pull the relays to check the ohms. Fan 2 relay with 5 prongs, had three copper color prongs and two silver prongs. Only the silver prongs had ohms of 114.5. Fan 1 relay had two copper color prongs and two silver prongs, and silver prong ohms was 110.6. MIG/CLT relay was two copper and two silver and the ohms was on the silver prongs were 170.5.

I need a easier understanding on how to run 12 volts to the relays to test them.

Thanks for the help.

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One each relay with two copper prongs, place one silver terminal to 12volts, the other to ground. The relays should make an audible click and you should go from infinity (= open circuit) to continuity, 0-1ohms.
One the relay with 3 copper terminals, at rest there should be open circuit between say 1 and 3 (my nominal markings) and continuity between, say 1 and 2. when you again short one of the silvers to ground the other silver to 12volts, again an audible click and then say 1 and 3 will have continuity, 1 and 2 open circuit. Hence 1 is common (= 30)
2 is normally closed (= 87a) and 3 is normally open (=87). Also known as a SPCO or single pole changeover.
See diagram.A21_untitled.bmp

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Now probe the slots on the relay bases where the copper terminals went. on the four terminal bases one of each should read 12 volt live, one the 5 terminal one of the three.
If not turn on the engine, now loop from the live to the other base for the copper terminal with a piece of wire, do the same for the 5 terminal to the one that joins to the live when the relay is powered up. Turn on engine, select AC with the fan at speed one.
Everything should work, and check that feed to the compressor for 12 volts, in fact you might have heard the compressor clutch plate kick in.
Everything should now work. If not it's an AC pressure switch or ECU problem.
If it works replace one relay at a time till it fails, that's your answer.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

That is great, I will try it tomorrow and let you know what happen.

Thanks, getting closer.

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I did the testing. Thanks for making it easier to understand. I did the 12v test to the three relays, all of them made a click sound. Fan 1 relay is for when the water temperature get hot and that work. I pull Fan1 relay out when the fan came on and fan shut down. I put the relay back in and fan came on.

With the relays out for Fan 2 and M/G CLT, I check terminals for power. The 5 terminal there is three across, the two outside terminal are silver and the one in the middle is copper. The one outside silver one had power only when the engine is on, I jump from one silver terminal to the other silver terminal and nothing happen. I tested the M/G CLT terminal and one silver and one copper terminal had power when engine was running , I jump the two and nothing happen. With the relays all put back in still no power to the compressor. Can I run 12v wire to the black & white wire that goes to the compressor.

I was tightening the hood latch when I drop the socket wench down by the front of the compressor. I start the engine and try turning the control nob for hot and cold, hot work but not the cold. But I notice on the dash red symbol, I look it up in the car book and it for the air bags and it just staying on. I know I didn’t do anything with the air bags. I remember seeing a black metal box with wires going into it where I drop the socket wench. I disconnect the battery and took two bolts off and got the metal box up to look at it. It was rusty, I disconnect the connect wires, there a plastic box inside the metal box, with two tiny terminal. I don’t know how to test this. On the menal box there a label saying Senor, Air Bag. FH. Toyota 89173-12100 187600-4990 Denso RH.

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I just saw this post. I have uploaded the wiring diagram for you A/C system to this site. There are other sensors that may be causing your problems and you may need to check all of them to determine the which is your culprit. The diagrams should get you started with the components involve, hope this helps.

A/C wiring diagram

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This information is provided only as a reference.
All circuits should be verified with a digital multi-meter prior to making any connections.

Thanks, I will check it out,

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I finally got chance to 12v on the black & white wire going to the compressor and the clutch engage.

I went back to the relays and pull out M/G CLT relay that I tested before and heard a click. I hot wire again where the relay was this time touching more then one setup and the clutch engage. I bought a new relay , will put in tomorrow, it to hot and humid. Was $15.00 dollars for the M/G CLT relay. The air bag relay, my wrench mash the connector when it fell, will work on that after the A/C is working. Thanks for your help, learn a lot and now I have good cheat sheets to use and learn.

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I bought a new M/C CLT for a/c magnetic clutch relay, clutch didn’t engage. Pull that relay out and hot wire and the clutch engage. Test the new relay it tested fine.

Then I went to Fan 2 relay pull it out and tested the terminals in the junction box this relay has 5 terminals. With the car running and a/c switch on, there was no power to the two silver terminals, but on the relay it self there continuity and ohms between the two silver terminals. There was power between one silver and one copper terminal. Between the two silver terminal is one copper terminal, with one silver terminal and the center copper terminal there power, switching to the other silver terminal there was power. If the two silver terminal on the relay tested with a click with 12v test, how will it work in the junction box with no power to the silver terminal.

I found this , but can’t find where it is.

The cooling fan < color=#810081 face=Arial>relay is located　below bumper fascia at right headlamp.　The ground for the < color=#810081 face=Arial>relay is at the headlight as well. the < color=#810081 face=Arial>relay is controlled by the pcm, so if you had a bad coolant temp sensor, this would cause the pcm to control the fan incorrectly, and possibly trip a check engine light. more than likely you have a bad connection or relay.

I found this too, I been looking but can’t find it.

If I remember the wiring I saw before, the relay is actually on the compressor some where (this is the reason it was overheating)

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