The idle up system has not been functional on my 87 Brat since the day I bought it in 1993 with @63K miles; has 145K miles now. It has the dealer installed AC setup with the idle up vacuum motor mounted with three relays on the right strut mount. If I remember correctly, one of the tubes to the idle up motor was connected to the vacuum line going into the firewall via a Y-connector (there may be a check valve to this line as well). However, I am not sure, it has been several years since I took the Y connector off etc. I need to hook the vacuum motor back up and get the idle speed compensated when the AC runs. Would someone have the plumbing diagram for the vacuum motor connections. My vacuum motor and/or the diaphragm (with an arm that pulls the throttle when the AC is turned on) might also be bad, and I will have to source these components as necessary. However, I want to plumb everything correctly and test it out prior to throwing new parts blindly. TIA.

PS. Is there a simple way to check the vacuum motor?

Edited June 5, 20205 yr by aba4430
Minor add.

Pick one of the manifold vacuum ports.  Put a T in the line.  Connect it to the vacuum motor.  see if it pulls.  Notice if it changes the idle once it has stabilized.  Pull it off, and block the hose [kink the hose] to keep the vacuum, see if it holds position.  If it isn't leaking, it should stay still.

Over here in Oz they used a vacuum switch - only operates when the AC compressor is engaged. 

There is a vacuum line from the manifold to this switch device, then another one from the switch to the diaphragm to up the idle revs. It’s that simple. 

There will be two ports on the vacuum switch device, I’m not 100% sure if they’re specific to which side needing to go to which part.

Cheers 

Bennie

Thank you DaveT and Bennie. Will troubleshoot and provide an update.

Here is a decent troubleshooting guide from Auckland.

Testing Vacuum Solenoid Valve

OK, my vacuum switch checks out OK. However, when I pull vacuum on the diaphragm with a hand pump (loan-a-tool at Autozone) I hear a hissing leak every stroke. I will pull it out and play around with some adjustments, but believe I will have to source a replacement. Any leads (Toyo, Nissan, Mitsu, Suzuki equivalents) appreciated.