Help Diagnosing AC Not Working

New to the forum... although I have found a lot of helpful information already.

I recently picked up a 2006 Tacoma and I know very little about it's history. However, the AC does not work. I am trying to troubleshoot and this is what I know so far...

• New in cabin air filter
• Blower fan works
• Heater works
• AC switch LED illuminates when engaged
• Fuses are good
• AC relay works (tested outside of vehicle)

I honestly can't tell if the compressor clutch is engaging or not. I can't see any change in behavior at the compressor. When I flip the switch, the engine idle does not change at all. (if that helps)

Can anybody clear up for me how the relay under the hood is supposed to be switched on? It seems to me like the ground is switched on and off when the AC dash switch is engaged, but I can't get the pin in question to ground with switch on or off. The pin in question does nothing... no 12v or ground regardless of key or switch position.

Pin in question is the one I have not marked.

If this pin is supposed to ground when switch is engaged... any ideas where to start looking for the solution?

Thanks.

 

You are probably low on R134a Charge which will prevent the compressor from energizing to protect the compressor.

1st step have the coolant charge checked.

 

Thanks for the feedback Jimmyh...

I got one of those R134a kits in a can with a gauge on top. Once connected to the low pressure side with engine running it read 0 psi. This was with engine running, AC on MAX. Per instructions on the can, I added enough R134a to get PSI to read in the green range (about 45 psi on can guage).

I noticed a change in idle, indicating the compressor kicked on... but only lasted for a few seconds. Then AC dash indicator light then began to flash. Still no cold air. This would repeat every time I turned the AC switch off and then back on again. Steady AC light and idle comes up for a few seconds, then idle drops with flashing AC light.

I ran a voltmeter from the connection in the relay box I could not get a ground on. Sure enough, when I hit the AC switch, ground is made but just for a few seconds... then AC light flashes, ground goes away.

My guess is there is not enough R134a in the system, so the compressor is only running for a few seconds before the pressure switch turns the compressor off. Thing is, I am not sure how to get the R134a pulled through the system without the compressor running.

Should I just keep adding more R134a until there is enough pressure to keep the AC pressure switch on, and thus compressor running? I don't want to put to much R134a (high PSI) and risk damaging the system, causing a leak. Directions suggest adding "half the can" if compressor is not running... but there is no real way to measure that amount.

 

Do not buy those suicide cans!! Take it to a shop and get the system properly evacuated and recharged. I need 4 things to diagnose your ac system
High side pressure
Low side pressure
Ambient air temperature
Duct temperature

 

Odds are high, if all electrical is in order and compressor in good shape, you already have a leak. It's why there's no refrigerant.

The system has to be vacuumed and hold a vacuum. Removing the air and moisture in it. You can't compress the air that has replaced the leaked out refrigerant enough to hold enough refrigerant.

Then, if there is a leak, it won't hold the vacuum you pulled; it will refill with air.

Also, refrigerant is the 'carrier' for much of the lubrication. So a fair amount of it has leaked and needs to be refreshed. And if the system really has been fully discharged, a new accumulator is in order, AFTER the leak is found and repaired. Once it will hold a vacumn, then it can be charged.

At this point I'm 'assuming' the electrical bits are all working and the compressor is actually functioning.

Lots of potential leak points, but unless you can see a blatantly obvious hole in something like the condenser or a hose line, you're not likely to find it w/o a sniffer or dye tester. Even then, if the leak is under dash in the expansion valve or evaporator it can be tricky to find.

@Bebop is right. This one requires, at a DIY minimum, someone with the right tools and diagnostic skills. Or most likely a regular shop.

 

This is the right answer ^^^. Sorry If you interpreted that I meant this was a do it yourself job with one of those suicide cans of 134a.

Take it to a good shop and have it repaired right.