Doc279

Anybody got any idea where the A/C amplifier is located on a 1990 4 runner ?

My A/c has been charged this year and works good when it decides to work.
I am having an electrical problem where the clutch does not lock up. Sometimes I can shut the ignition switch off and restart the runner with the A/c switch on and it will then work. Someday's it will not come on no matter what. - when it does work it is cold as can be.

I've already replaced the A/c cut off relay - The shop that charged the unit told me that the amplifier was probably defective.

A picture would be GREAT !!!

eric-the-red

The manual says it's located either on top or in front of the evaporator housing, behind the glove box. If you give me an eamil address I can send you the entire section from the factory manual. It has testing instructions for the amplifier.

Doc279

Eric - thanks
dstaley@searay.com

4Crawler

iTrader: (3)

Yep, usually behind the glove box. Has a knob labelled "RPM". Adjust the cut out RPM to be below your normal idle speed and that should do it. And then make sure the idle up valve on the engine is being kicked in with the A/C. There is usually a VSV that passes vacuum from the intake to the idle up valve, which will have an adjustment knob to turn the extra air up or down as needed.

Doc279

Thanks Roger

Do you think that this could be the problem ? Some days it works fine and then it will not come on for several day's no matter what. It is an electrical problem - I have no voltage on the wire that turns the compressor clutch on. It is weird because it works fine when it works.

Sometimes I can just shut the runner off and re-start the engine and it will come on. This thing is hard to figure out !

4Crawler

iTrader: (3)

One way to tell, turn the RPM knob down and see if it comes one the next time it won't work. Might also be the low pressure cutoff switch.

Doc279

I'll have to check this tonight - prior to replacing the A/c cut off relay
I jumped the low pressure switch with a jumper wire. no dice on the compressor working. I gave up and took the runner to a A/c specilist shop
and they added R-12 freon. I know the system has pressure.

I found a trouble shooting guide from a 1993 on-line service manual - I will check all this tonight. I am still looking for the A/c amplifier.
The local dealer tells me that the amplifier is slid into a slot on the blower/ heater housing - no mention of a knob - I'll try and post a picture tomorrow. A/C amplifier cost $60.00 at Toyota of Knoxville - sister works there - nice discount !

Bigblock

whats your idle speed and engine temp?