Compressor coil won't trigger

[CO MJ]

I am currently converting my AC system over to r134 and trying to tell if my compressor is good. I currently have empty lines, so have a jumper on my low pressure switch. I thought by jumping the switch, I'd be able to see if my compressor clutch engages or not, and alas, it does not. If I jump the compressor coil wire straight to the battery, it kicks on just fine. My coil resistance is a hair low at 3.4, but within spec I believe. I did notice I am reading 14.5v on my battery, but only 11.5 at the clutch coil when the engine is on.

According to the diagram, it looks like the voltage path is battery, to the fuse box, c120, c100, through the low pressure switch, to the clutch relay, c309, to the coil. I've checked all these connections and they seem pretty clean. I suppose I could be getting some voltage drop from the original harness itself, in which case, big bummer because that's not getting replaced any time soon. 

I've tried various combos of climate control settings and that doesn't not appear to have any effect. Another note is my rad temp switch is jumped so the fan always runs, but that doesn't seem to me that it would cause issue. 

Anyone know of some other magic that might be the reason I'm getting that low voltage at the clutch, or if that's normal at any point?

Edit: I also just noticed the blower fuse is getting very hot while the engine is on

Edit Edit: If I set the blower to minimum the fuse doesn't get as hot and I can get the compressor clutch to kick in

[Ωhm]

51 minutes ago, CO MJ said:

I currently have empty lines, so have a jumper on my low pressure switch. I thought by jumping the switch, I'd be able to see if my compressor clutch engages or not, and alas, it does not.

 

AC Clutch Relay coil side (C241_5) is supplied voltage from the Fuel Pump Relay (FPR). At KEY ON the FPR will time out within 2-3 seconds causing NO VOLTAGE at C241_5 causing NO CONTROL for the AC Clutch Relay. Could be your problem.

[CO MJ]

22 minutes ago, Ωhm said:

 

AC Clutch Relay coil side (C241_5) is supplied voltage from the Fuel Pump Relay (FPR). At KEY ON the FPR will time out within 2-3 seconds causing NO VOLTAGE at C241_5 causing NO CONTROL for the AC Clutch Relay. Could be your problem.

My relay is on and I do have voltage at the clutch coil though, if that was is I shouldn't have any power to the coil. I think something is causing my blower to draw excess current, bad ground or a blockage in the vents maybe, making the voltage sag too low for the coil to pull in the clutch.

[Ωhm]

All of this is being performed with the ENGINE RUNNING?

[CO MJ]

3 minutes ago, Ωhm said:

All of this is being performed with the ENGINE RUNNING?

Correct

[Ωhm]

Known issues with the Blower Motor circuit is overheating at the IGN SW.

 

 

 

[CO MJ]

3 minutes ago, Ωhm said:

Known issues with the Blower Motor circuit is overheating at the IGN SW.

 

 

 

That's a good one, I'll check that as well. Would you expect the turn and radio fuses also to get hot in that case? Mine are not

[Ωhm]

High current draw (amps) would be the Blower Motor and the Cigar Lighter while low current draw would be on the lights and radio.

[Eagle_SX4]

Sounds like your blower motor may be on the way out. I had a problem with blowing the thermal fuse on the blower motor resistor. Couldn't figure it out went through 3 blower motor resistors before I checked the blower motor draw. It also did not sound bad (wasn't squealing or grinding). Just something else to check.

[CO MJ]

On 3/10/2023 at 10:06 AM, Eagle_SX4 said:

Sounds like your blower motor may be on the way out. I had a problem with blowing the thermal fuse on the blower motor resistor. Couldn't figure it out went through 3 blower motor resistors before I checked the blower motor draw. It also did not sound bad (wasn't squealing or grinding). Just something else to check.

 

Good call. I will have to pick up a current clamp. Any idea what normal draw for the blower would be?