1993 f150 A/C compressor doesn't cycle, no voltage at plug

Moderator: Mod Squad

Humming
Registered User
Posts: 24
Joined: Sat Jul 15, 2017 11:52 am

1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #1 by Humming » Tue Sep 18, 2018 5:33 pm

Hello, I have a 1993 f150 that does not appear to have been converted to r134 yet. When I turn on the AC, air comes out the vent but it is not cold. I popped the hood and the compressor doesn't cycle. I pressed a valve and not much pressure came out. I pulled the plug on the compressor clutch and couldn't measure any voltage across the pins or from either pin to ground with the engine running and AC on.

Where do I go next isolating the problem? Add refrigerant and try again? Or is it definitely electrical and I need to keep teaching back from the connector to see when I finally get voltage?

User avatar
bubba22349
Global Moderator
Posts: 8326
Joined: Sun Jan 03, 2010 4:46 pm
Location: Flagstaff, Az. 86005 near the old Route 66

Re: 1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #2 by bubba22349 » Tue Sep 18, 2018 6:28 pm

If there isn't any freon in the system due to a leak or leaks the compressor won't work until that's taken care of, or its refilled. Ie it has a pressure switch in the system to protect it. Good luck :thumbup: :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

Humming
Registered User
Posts: 24
Joined: Sat Jul 15, 2017 11:52 am

Re: 1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #3 by Humming » Tue Sep 18, 2018 8:44 pm

bubba22349 wrote:If there isn't any freon in the system due to a leak or leaks the compressor won't work until that's taken care of, or its refilled. Ie it has a pressure switch in the system to protect it. Good luck :thumbup: :nod:


I was hoping this would be the case. I'll drain and fill tonight. If it then works awesome, I'll let it be until it leaks out, then I'll replace all the o-rings and the receiver dryer.

Humming
Registered User
Posts: 24
Joined: Sat Jul 15, 2017 11:52 am

Re: 1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #4 by Humming » Tue Sep 18, 2018 11:23 pm

Well, i pulled vacuum down to about 27 inHg, closed the valves and it held it steady for twenty minutes. I added in r134a(the system is still an r12 system but if it's broke I'm converting it anyways) with the engine running, the compressor would cycle but it really wouldn't take more than about half a can, it just wouldn't flow in anymore. At that point the gauges were reading about 140psi on the high pressure side and 30 psi on the low pressure side, and the air wasn't getting any cooler at all. Compressor was ticking like mad too, so I figure it's about to go.

So it seems like my ac system is toast. One other curious note, if I turn the AC to anything other than high, it quits blowing at all. Doesn't get cool on max or norm.

I should also add, this truck is new to me so I'm still learning all the quirks and each issue I mention is not necessarily a new development.

So, inadequate pressure difference, noisy compressor, doagnosis: new system required?

Thanks in advance

User avatar
B RON CO
VIP Member
Posts: 688
Joined: Tue Apr 05, 2016 7:02 pm
Location: Long Island, NY
Contact:

Re: 1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #5 by B RON CO » Sat Sep 22, 2018 8:21 am

Hi, did you add the 134A with the engine off? If so, run the engine, a/c on, and you should get the most of 2 cans in on the LOW side ( I can never get the cans to completely empty). Stay away from the HIGH side. I would only hook up the LOW side when you try it again. In the driveway the HIGH side is only for diagnosis and can be a real danger if you add 134A.
Is the ticking noise the clutch cycling, or is the clutch locked on and the noise is internal? If the noise is internal the compressor is toast. If the clutch is cycling try another can of 134A. Maybe a can of 134A with oil is better.
If the system is in good shape it should work with 134A.
The easiest way to look for leaks is to check every connections for oil and the dirt the oil attracts. If the connection is clean the connection is good.
I don't know why the controls inside are not working. How does it blow with the heater? There is a resistor for the blower motor.
Good luck
B RON CO. Still workin' on it!

1933 Ford Pickup - 59A Flathead V8
1966 Ford Bronco - U14 - 170/200 Straight 6
1966 Ford Mustang - 289 V8

Humming
Registered User
Posts: 24
Joined: Sat Jul 15, 2017 11:52 am

Re: 1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #6 by Humming » Sun Sep 23, 2018 5:15 pm

Thanks B RON CO, I have full gauges with valves so it let's me read hi side pressure without connecting the hi side to the can.

I could only add 3/4 of a can with the car running, maybe if be able to add more when it's off?

Heater works fine but does the same thing, blows great on full blast, shuts off entirely once you turn the speed down at all.

Had a few people suggest the blend door as a culprit so i'll check that out.

Definitely the compressor itself that's ticking. Just hoping to get another month or two of service out of it and then replace it all in the spring.

B RON CO wrote:Hi, did you add the 134A with the engine off? If so, run the engine, a/c on, and you should get the most of 2 cans in on the LOW side ( I can never get the cans to completely empty). Stay away from the HIGH side. I would only hook up the LOW side when you try it again. In the driveway the HIGH side is only for diagnosis and can be a real danger if you add 134A.
Is the ticking noise the clutch cycling, or is the clutch locked on and the noise is internal? If the noise is internal the compressor is toast. If the clutch is cycling try another can of 134A. Maybe a can of 134A with oil is better.
If the system is in good shape it should work with 134A.
The easiest way to look for leaks is to check every connections for oil and the dirt the oil attracts. If the connection is clean the connection is good.
I don't know why the controls inside are not working. How does it blow with the heater? There is a resistor for the blower motor.
Good luck

User avatar
B RON CO
VIP Member
Posts: 688
Joined: Tue Apr 05, 2016 7:02 pm
Location: Long Island, NY
Contact:

Re: 1993 f150 A/C compressor doesn't cycle, no voltage at plug

Post #7 by B RON CO » Sun Sep 23, 2018 8:12 pm

Hi, yes, I use an a/c manifold gauge set too. Just wanted to make sure you know the high side can lead to danger and damage.
Look for the blower motor resistor. It could be under the hood into the heater box. Just a plug and a small rectangular deal in the air flow.
Fords usually last forever, but I have seen them packed with leaves and all kinds of debris.
Good luck
B RON CO. Still workin' on it!

1933 Ford Pickup - 59A Flathead V8
1966 Ford Bronco - U14 - 170/200 Straight 6
1966 Ford Mustang - 289 V8

Who is online

Users browsing this forum: No registered users and 3 guests