Vacuum leak

[KJoeZ61]

Over the summer I had the heater box rebuilt professionally and I replaced the a/c & heater switch on my 71 Scamp. Actually the whole car is being redone and rewired. Anyway I have no vacuum which I'm looking for the leak now. My question is do I need vacuum for the switch to energize the a/c system. When switched to a/c I have no power going out to the compressor. And no there is no a/c system yet under the hood. I'm still in trouble shooting mode, just trying to figure some stuff out.

 

[340duster340]

if your system isn't charged there is a pressure safety switch so you don't burn out your ac clutch. at least that's how it works on the newer cars.

 

[KJoeZ61]

Just to clarify there is no a/c system yet installed. I am not getting power to the safety switch wire. In other words I have no power going out to under the hood. Just trying to figure out why not.

 

[krazykuda]

Have you tried tracing the power wire to the switch to see if it's got power?

Was the car originally heater only or A/C from the factory???

For the blower motor power, the heater only gets the power into the blower switch directly... With A/C the main power wire goes into the vacuum unit first, then to the blower switch... Make sure that the power in/supply wire has power...

 

[KJoeZ61]

Have you tried tracing the power wire to the switch to see if it's got power?

Was the car originally heater only or A/C from the factory???

For the blower motor power, the heater only gets the power into the blower switch directly... With A/C the main power wire goes into the vacuum unit first, then to the blower switch... Make sure that the power in/supply wire has power...

Yes its a factory a/c car.

I have heat and the blower motor is working. But there is a open vacuum leak that I'm trying to find. When I test the hose going from the engine compartment back to the firewall under vacuum there is none! The engine runs fine and creates vacuum, that's not the issue. My question is that why I have no power going out for the a/c? Dose the a/c heater vacuum switch need vacuum to allow power to go to the compressor? If so that's probably my problem.

 

[krazykuda]

Yes its a factory a/c car.

I have heat and the blower motor is working. But there is a open vacuum leak that I'm trying to find. When I test the hose going from the engine compartment back to the firewall under vacuum there is none! The engine runs fine and creates vacuum, that's not the issue. My question is that why I have no power going out for the a/c? Dose the a/c heater vacuum switch need vacuum to allow power to go to the compressor? If so that's probably my problem.

I'm not sure... We just got ours started recently and now must finish more work to get it on the road again... We haven't gotten to the point to run/check the blower motor...

We ordered a new heater only harness for our original A/C car, but then decided to keep the A/C duct box as we didn't want to fill in the holes for the evap lines...

I had to convert the heater only harness to fit the A/C set-up, but it wasn't too bad once you figured out the wiring...

 

[krazykuda]

Are you getting vacuum on the main vacuum supply line into the harness/switch???

 

[KJoeZ61]

I didn't get the engine running until late fall and there was a bad vacuum leak. At that time I disconnected the line leaving the intake and capped it off to solve that problem. With that said I knew there was a vacuum issue under the dash. So what I did yesterday using a hand held vacuum pump with gauge attaching it to the line going into the dash and after pumping it I get nothing. to be honest I'm not overly concerned about the heat, I need the a/c here in eastern Pennsylvania. I did replace the vacuum switch with one from Classic Industries. It's not easy getting to that switch, guess ill be pulling the ash tray, radio and looking closer.