a/c compressor relay

why do i keep burning up the a/c relay

 

Because you're so hot Ricki Lee

 

How many have you been through?

 

A few more details might help

 

"burning out" the coil or the contacts?

 

sorry i tried to make it more clear before posting but it just went away, anyway it's 2009 4wd 4.0 replaced one and it worked for about an hour ( got it from autozone not my favorite but they had one not by listing but from old part #) so got another lasted about 5 min. then oh it's autozone so got a factory one same thing, i think it's in the a/c clutch ( short circuit?) pos. a/c amp.? going o jump terminals with a fuse in between to see if it blows the fuse, the comp. works fine with no noise (when working after relay replaced. thanks all

 

ps replaced water pump 1 1/2 months ago so had to take comp. loose to do this (had to just get out of the way) to remove drive belt tensioner, maybe i disturbed the grd. wires? the contacts do not seem to be burnt

 

I'm not sure what the relay looks like? Plug in? Can the bad one be tested with a meter?? Check the Coil to see if it's burned/open? If possible open it (even if a highly calibrated hammer is required) and inspect to see if the points or coils are burned /shorted??

There may be two fuses for this?? - one for the coil of the relay, One for the power line for the clutch. I would check to ensure that the correct value fuses are in place - especially the hot wire for to/from the contact on the relay that will drive the Clutch.

The Fuses should be blowing before the relay gets toasted. - this includes the coil of the the relay AND the power wire for the Clutch.


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Update - I found some schematics - I'm checking and will advise

While I peruse the prints - the following will be helpful
Check the Coil to see if it's burned/open? If possible open it (even if a highly calibrated hammer is required) and inspect to see if the points or coils are burned /shorted??

 

I found some 2006 schematics. "IF" these are accurate I see the following.

There is one fuse for the Clutch relay AND the AC clutch. I see a 10 A fuse IG1 #2. WE need to find out (as cliffyk said) - what burned out on the relay. Out from fuse looks like a "LG" wire (Light green?). This goes to pin 2 (coil) and pin 5 (pwr for clutch). Pin one (G / Green?) goes to the AC amplifier (Module?) - this is the coil for the relay to pull in. Pin 3 (V / Violet?) goes to the Compressor Mag Clutch. There is a GROUND on the compressor shown. IT may be internal or a separate wire. Since you "Moved" the compressor be sure all wires/grounds and contacts are OK at the compressor.

Now - Did the Relay coil fry = or did the contacts blow? You need to get the relay apart and let me know .....

 

What are you calling the A/C Relay? I know that sounds stupid bit there are two relays associated with the A/C System. As far as I know ( looking at the schematics ) there is no relay labeled as an A/C Relay...

1.) Heater Relay - Provides power to the Blower motor, And the AC Amplifier Black Wire with a Yellow stripe that controls the three servomotors through a 10 ampere fuse labeled " A/C ".

2.) MG CLT Relay - Provides power to the Magnetic Clutch Coil and the Clutch Lock Sensor through a Violet Wire.

We need to know what your symptoms are before any detailed assistance can be given.

When the relay goes out does the Blower in the cab run? If the answer is no then we must be talking about the Heater Relay circuit.

When the relay goes out does the clutch on the A/C Compressor energize? If the answer is no then we must be talking about the MG CLT Relay Circuit.

 

I also think your issue may be related to the famous blower connector and resistor issue stated in this post: https://www.tacomaworld.com/threads/fan-speed-switch-not-working.70275/

Maybe not, but it gives you some more information. If this is your issue this is what you need to fix it:

You may have a burned resistor connector and may need these:

Plug Number

$32 82141-04M40

82141-04M40
Resistor Number 87138-04052




Part number

$13 90980-10916 6" 12ga Harness NEW

90980-10916 Connector

Part Number

$11 82998-12380 90980-10916, 6"es 12 Gauge Wire Harness

82998-12380 Wire and terminal

Not sold as a kit, sold as each.

Connector:





Terminals:

 

As Always - Jimmyh thanks for the clarification ...

 

Your description of the Magnetic Clutch circuit was spot on. I was a just bit confused by his description... I still am a bit. I was wondering what made him think it was a clutch issue other than the fact that it was disturbed in recent history. It would be good to know what his exact symptoms are however. It is hard to imagine burning out a relay in 5 minutes without blowing a fuse somewhere.

I am leaning towards the blower motor connector, resistor more so than a compressor clutch problem. Without any more facts it is very difficult to say with any accuracy. I hope he reports back soon.

 

Agreed - we need clarification on which relay .... But if it is the clutch relay .... then - maybe a Stupid thought .... OP said he messed with the Compressor to replace the water pump. Is is possible to "Force" the connector to the compressor on backwards??? SG White (signal ground for the AC Amp module) possible to get shorted to Violet (clutch on). "If" the relay contacts blow at less than 10 amps it "kinda" fits the problem. Just conjecture at this point - but fun to guess .....

 

With my 40+ years working with electrical and electronics I have learned anything is possible. HA!

 

first thanks all for your help, it's the mg clutch relay, all fuses are good the a/c worked fine for 6-8- weeks after moving comp. have a service manual with wire diagrams my update is i put a fused connector between the post of the relay that go to the clutch ( relay removed) the fuse used is a 3 amp and did not blow and a/c working fine so i figure if there was short between fuse box or the clutch or anywhere a 3 amp fuse would blow so am now going see if i can check the a/c amp. circuit , not sure how a blower motor resistor could be the problem ( have replaced many for motor speed prob.like a 100) but like was said over the years yep anything is possible,, bad grounds a major issue in many, many cases like turning on the lights and the wipers take off

 

oh and the coil side is what goes out the point contacts are fine get no ohms on coil pins of relay

 

The clutch relay coil is supplied with +12V on one side, and grounded by the AC Amplifier (control module) to activate. The FSM states the voltage at the MGC terminal of the module (pin 21, a green wire) should be 10-14 V with the clutch off and < 1.0 V (grounded) with the clutch energised..

Have you monitored your system voltage? As the relay coil is seemingly rated for 10-14 V I would check that the system voltage is not too high and overloading the relay coil--it's a long shot however I cannot see how the relay coil would burn out otherwise?

 

thanks looks like a/c amp. does the grounding to excite the relay to close circuit checked that side for ground got nothing have pos. to both coil and clutch side s i'm thinking maybe a/c amp. not grounding properly and relay is finding ground via other devices but that is not sufficient enough so, to much power for not a good ground. all voltage seems good ,, not sure where the amp. is located though

 

I assume you checked the MGC pin on the amplifier when the system was (supposed to be) calling for the clutch to be engaged--that is of course when it would be pulled low. If not calling for the compressor to run then + system V would be read--though the coil with no current flow...