Aftermarket Radiator & Electric Fans

[SCOTI]

Originally Posted by hatzie

With the larger than stock fan you are moving enough air through the stack at idle and sedate cruising but the compressor cuts out when you get in it. Over 30mph the fan is not moving more air than the road speed is pushing through the stack.

At WOT the ECM on a TBI engine should kill the AC compressor til you back off the go pedal. Not sure if all of them do. It gives you a temporary HP boost for passing etc. My 76 has a WOT compressor kill switch on the 6.5L diesel. I installed it on purpose.

If this is not a WOT kill switch... you are describing an overcharged AC system or a failed or incorrectly sized HPCO switch.

This rings a bell. Are the HPCO switches adjustable? I seem to recall reading some info on something being adjustable.

[hatzie]

WOT is Wide Open Throttle...

I don't recall reading anything about the HPCO switches being adjustable. You need one set for R134a not R12.
Some older LPCO switches are adjustable.

[gmachinz]

I have some aftermarket R134 "retro-fit" LPCO switches and they are adjustable much like an aftermarket vacuum advance or a TH350 modulator.

I remember one time after converting a friends system over we flushed it out, blew thru it all with compressed air, ect. and it had some weird high side readings too-turned out after taking it all back apart and inspecting everything we must have missed a couple things-most notably was a bees' head and thorax stuck to the inlet of the orifice tube screen. My buddy suddenly remembered he did leave the system open for a few weeks-never did he think a bug would somehow get inside the AC line.

[SCOTI]

My evap was not connected to the remainder of the system for an extended period but was capped & taped off immediately after disconnecting.

The evap & lower line were flushed prior to reassembling the system. The disharge was relatively clean.

I'll look up the specifics of the pressure switch & will share what I find.

[SCOTI]

Still haven't dug into the pressure switch.

I did play w/the Aux Fan tonight. I looked through the schematic that I have & compared it to notes I had recorded during the build. I made a notation of all the switches that were installed on the motor & their location during the motors disassembly/reassembly. One of the temp switches is in the PASS side head & is for the Aux Fan. That got me wondering so tonight I disconnected the wire going to it @ the block & connected 12v power to that wire. I then checked the plug that connects to the fan motor & now have 12v power.

So it seems that temp switch & whatever it connects to is my issue for the Aux Fan (I could hear something else clicking under the hood when I put 12v HOT power to the wire). My schematic doesn't really indicate much for the A/C comp circuit.

Also noteworthy is the fitting we replaced last Thursday was the source of the leak. When I moved the truck today the air was coming out of the vent @ ~60°F so it hasn't lost the charge.

[nekkidhillbilly]

word of advice on flex a lite. I had one of there fan controllers on my 01 Silverado with lt1 fans. it kinda melted the ground. I use derale since then no problems. dad has had the controller for 10 years.

[SCOTI]

So I want to test out if the Aux electric cooling fan makes an impact. Would I be ok wiring it up like so:

Ign switch power source to a toggle switch.
Toggle switch to a 30amp/4-pin relay.
30amp relay (Batt hot; ground; on signal from toggle switch).
Batt power from relay to Aux fan.
Chassis ground to fan.

I don't know & haven't been able to find the tech info on these GM spec'd aux cooling fans. I don't want to worry about having a wiring meltdown but would like to just toggle the Aux fan on when the a/c is active.

Thoughts?

[hatzie]

I think that's the only time they ran em but don't quote me on it.

[SCOTI]

Still @ it....

I purchased the pieces necessary to run a manual toggle switch for the Aux fan. While looking @ the engine compartment layout on where I could mount the relay w/o adding clutter, I noticed (remembered) there was a factory GM weatherpak style relay already mounted on the driver side inner fender w/room for another.

I googled the part # for that relay & sure enough one of the results said it's for the Aux cooling fan on GM vehicles. I went back through the wiring schematic again & got my buddy involved that's a little more up to date on GM's wiring & relays. We came to the conclusion the relay is not seeing a ground to complete the switched loop through it. So I tested the theory out.

With the truck running & everything plugged in like factory, the fan doesn't run even w/the engine obviously hot & a/c switched on.
With the lead to the temp switch for the Aux Cooling circuit disconnect from the switch & grounded to the chassis, the fan runs. So the temp switch is not opening the ground circuit when the engine is @ temp.

I'm not sure if the switch is bad (it was replaced w/all the other sending units before the motor went back in after rebuild). Or, is something else @ fault (Teflon tape on the threads??)?

Not sure if others have experienced this so I thought I would share my findings.