Guidance on Testing Relays per FSM

[Farrell Martin]

I hate and don't understand electricity, so want to make sure I understand what the FSM is saying. I am in the process of following the FSM steps to troubleshooting my AC not blowing cold air and the first step is to test the magnetic clutch relay. The FSM says to do it the same way as it describes for the Blower High Relay. The diagram in the FSM is below. Can someone please explain in laymen terms how I would do what is described below before I fry, blow up or burn down something? Thank you F-

 

[mct75]

Connect a 9v battery (or 12v source if you have it) to terminals one and three. Listen for a click and see if continuity on two and four (ohms setting on meter) changes with the click.

 

[SmokingRocks]

This ^.

Don't be intimidated by electricity it takes some time to understand what the fsm is showing you but if you keep at it you'll figure it out. And once you do you'll be able to fix anything on your rig.

 

[Farrell Martin]

great, thanks for the info. F -

 

[LINUS]

Also, that chart reads like an English book - left to right, then next condition is next line down.

Also pay attention to 'constant' 'condition'/(switched) & not there but earth/ground.

Unless something is wrong, or weak, - these 3 states are all any wire will be.

I'll add that other makes of FSM / EWD are harder to understand, so really you are learning practical app in a good book.

Some EWD's (non-Yota) that you see with vertical circuits start with constant/hot at the top of the page & vert circuit paths flow to bottom of page.

 

[bicycleagent003]

As an electrical idiot, I would just like to say that I have learned a lot from the EWD with patience and a multimeter. I would just say really take your time and try to be curious. I've also watched a few YouTube videos about automotive electrical stuff, and those have been very helpful.
Electrical stuff is very logical and can be figured out, it just takes time.
Good luck.

 

[SmokingRocks]

Search for then save and print a copy of toyotas symbol key. Also remember that the double arrows do not denote current flow..

And the notes regarding voltages at certain pinnouts is very important this is usually last page of each section

 

[Farrell Martin]

Before I get any further with questions, let me go and say it is a '92 FJ80 with 73k miles.

Slowly getting my feet wet (and hopefully cold eventually)......tested what I believe to be the magnetic clutch relay. Following the diagram in the FSM there is potentially 2 relays next to each other - the magnetic clutch relay and a starter cut relay. I found two sockets, but only one had a relay in it, so I tested per the guidance above assuming it is the MCR. Put a 9 volt battery on it and it clicked and resistance changed in conjunction So, I reinstalled it.

EDIT: FURTHER READING IN THE FSM INDICATES STARTER CUT RELAYS ARE APPLICABLE TO 'H SERIES ENGINE'. BEING MINE IS A 3FE, IA M READING THIS AS I WONT HAVE THE STARTER CUT RELAY, SO THE RELAY I FOUND MUST HAVE BEEN THE MAGNETIC CLUTCH RELAY.

Next, I checked power at the 10A Air Conditioner fuse in the fuse panel - I get right at 12 volts when the AC is on so I know I am getting power there.

I decided next to run 12v direct from battery to the compressor and the compressor clutch immediately kicked on so I know the AC has the potential to return to its former cooling glory.

Next, I removed the trinary pressure switch and tried jumping it to see if the compressor clutch would kick on - no luck. So, my research continues.....

 

[Farrell Martin]

More observations.....

Step 3 in the troubleshooting section of the FSM says to Inspect Volume of Refrigerant using the site glass. Obviously this is pointless unless the compressor is kicking on, so I ran 12v direct from the battery again to get the compressor going just long enough to observe the site glass. There were a ton of bubbles in there telling me Freon is low. This being the case, my thought is the triple pressure switch may have shot down the compressor due to low pressure. If this happens to be the case, wouldn't the compressor kick on when I jumper the pressure switch?

Thanks