A/C Woes

[HtownManche]

Hello,

 

Updating my 1991 Comanche to have working AC once more. Having trouble with the classical AC compressor won’t engage problem while trying to fill with r134a. Tons of searching here, elsewhere, etc have not solved my problem. Perhaps I am

not searching correctly or using the wrong tags.

 

-all new parts throughout system (evap/compressor/condenser/drier/lines.

 

-attempted to fill with 134. Noticed compressor not engaging.

 

-went straight 12 v from

battery to compressor, verified clutch engages.

 

-jumped across coolant temp sensor in thermostat housing, no effect 

 

-jumped low pressure switch,

non effect.

 

-new relay. 
 

-removed relay, jumped across pins 30 and 87. No clutch engagement.

 

-Measured voltage at terminal 30-only getting 2.4 bolts, not 12. 
 

-Verified compressor feed line sees same voltage at terminal 30-2.4 volts.

 

-Voltage at pin 30 drops to 0 when I turn ac off in cab, and comes back when I turn it on

 

Where am I going wrong? 

[Ωhm]

909761367__JEEP1991SequentialFuelInjectionManual_1.pdf

 

Check out pages 38 & 39. Talks about A/C Select and A/C Request. Includes circuit drawing.

[Andy in Pa]

17 hours ago, Ωhm said:

909761367__JEEP1991SequentialFuelInjectionManual_1.pdf

 

Check out pages 38 & 39. Talks about A/C Select and A/C Request. Includes circuit drawing.

Yes, sounds like you need to start (as you have done) and keep going back until you locate the problem.  These attached schematics should help.  Although, remember the relay is energized by a signal, but the power going to the compressor comes from the set of contacts on the relay.  Maybe the relay is energizing, but the feed power to the N/O contacts on the relay is not getting power.  Is there a fuse for the AC comp?