Another A/C Question

[Striker 85]

Got my system charged, it was almost empty. The compressor will not kick in. Bypassed the low pressure line sensor and the system blows fine out the bottom vents, but barley a trickle out the top vents. So 2 questions for the masses

1. Bad Low Pressure Switch? That what I think, but I hate to evacuate all that R12$$$$ again to replace the switch.

2. Is there a vacuum relay that opens the ducting to the upper vents, or something else?

Thanks in advance. Gotta get this fixed before the drive to MAM funfest.

 

[vigman]

I'm with you

Question #1
Yes there are vac motors that control the ducting/ routing
and an electric motor to control temp ( in the Climate Control version )

Check to make sure that when you change modes.. ALL the other ducts work
EG defrost.. so you might have A broken line or motor( vac servo )

OR you have NO vac to the control head telling the servos what to do.


Question #2
I believe the port that the switch is on has a schrader valve.. you MIGHT be able to replace the switch with out losing the WHOLE charge. but someone else will have to chime in on that one. However if the system is exchanging ~ 15 to 20 degrees of heat ( eg the air in the cab is 60 by the AIR INTAKE for the coils and the discharge from the vents is ~ 34 degrees ) your doing fine.

Also check the drier bottle.. that should have a PILE of condensation dripping off it when it working properly.

The possible drawback from jumping the switch is pumping NO FREON when your low or out.. and the OIL for the compressor guts is suspended in the freon.. so no gas.. no lube.

All that being said.. gauges tell the WHOLE STORY.. the other info is rule of thumb.

Hope this helps

Vig~

 

[badabing9]

the blend door serves to regulate temperature. there is a vacuum check valve that is located behind the distributor (L98) that if bad, will give you the same symptoms as you are experiencing. 1 line goes to the plenum, 1 line goes to the cruise control, 1 line goes to the ac programmer module located under the drivers side dash and is about the size of a large pack of smokes. if the lines are loose, broken, detacked or if the ck valve is cracked or defective, you'll experience what you now have.**i am a bit unsure if this write up will apply to your 85 but, worth considering.

 

[badabing9]

Question #1
Yes there are vac motors that control the ducting/ routing
and an electric motor to control temp ( in the Climate Control version )

Check to make sure that when you change modes.. ALL the other ducts work
EG defrost.. so you might have A broken line or motor( vac servo )

OR you have NO vac to the control head telling the servos what to do.


Question #2
I believe the port that the switch is on has a schrader valve.. you MIGHT be able to replace the switch with out losing the WHOLE charge. but someone else will have to chime in on that one. However if the system is exchanging ~ 15 to 20 degrees of heat ( eg the air in the cab is 60 by the AIR INTAKE for the coils and the discharge from the vents is ~ 34 degrees ) your doing fine.

Also check the drier bottle.. that should have a PILE of condensation dripping off it when it working properly.

The possible drawback from jumping the switch is pumping NO FREON when your low or out.. and the OIL for the compressor guts is suspended in the freon.. so no gas.. no lube.

All that being said.. gauges tell the WHOLE STORY.. the other info is rule of thumb.

Hope this helps

Vig~

^^^^^^^^^^^^^^^^^^^^^^^^

"Question #2
I believe the port that the switch is on has a schrader valve.. you MIGHT be able to replace the switch with out losing the WHOLE charge."
***yes, it can be done. simply unscrew the lp switch as there is a schrader valve beneath it. then, simply screw on the new switch. if you have a bad schrader valve, THAT would require a special extractor tool to replace it w/o losing the charge.

However if the system is exchanging ~ 15 to 20 degrees of heat ( eg the air in the cab is 60 by the AIR INTAKE for the coils and the discharge from the vents is ~ 34 degrees ) your doing fine.
***as a point of maintenance, i would remove whatever cowling you have and clean all the crapola (leaves, bags, etc) from between the condensor and the radiator and then apter applying some simply green and letting it sit for a while, back flush it with a moderate but gentle stream of water.

Also check the drier bottle.. that should have a PILE of condensation dripping off it when it working properly.
***not necessarily but possible. it is wise to check the condensation drain hole beneath the heater/ac box and be sure it is clear for drainage.

The possible drawback from jumping the switch is pumping NO FREON when your low or out.. and the OIL for the compressor guts is suspended in the freon.. so no gas.. no lube.
***jumping the compressor is usually only done while troubleshooting and for a VERY brief period of time. it is also done while introducing refrigerant into the system while recharging. doing this (as above) will grenade your compressor and send it's internal parts throughout the system requiring each component to be flushed and dismantled.