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Compressor / Blower Wiring Upgrade

Muad'Dib

Muad'Dib

NAXJA Forum User
Location
Bend, Oregon
I haven't looked at a schematic yet... but i would like to upgrade the wiring to the AC Compressor and the blower motor. This will not only save OEM wiring loads (i think both of these run through the ignition switch...), the replacement large gauge wire will help lower voltage drop from using these devices.

For the AC compressor I'm sure its as easy as cutting the 12v supply and turning it into a trigger for a relay. Then just running a fused 10 gauge through the relay to the compressor.

I'm just not to sure about the blower motor though. Should i do something similar as i am thinking for the compressor to the blower motor before the resistor pack? I'm guessing that is the way it will have to be done in order to keep the different fan speeds working properly.

I have searched, and have read people hinting around the idea.. but i havent found anything solid yet as to someone who has done it and documented it in some way or the other.

Any comments on either task would be extremely appreciated.

Thanks for your time.
 
The 90 Renix blower does not go through a relay. It goes through the ignition switch, Red wire in, brown wire out, which also runs the turn signals, wipers, and radio. I forget what else is loaded on it. Electric windows too on mine I think.
I ran a new 10 gauge wire from the back of the fuse box, with a 30 amp fuse to a dash mount toggle switch on my 87, 3 years ago. I have a 10 gauge wire that runs straight from the blower to the battery with a big battery clamp running the blower on 85 currently. It has a 30 amp fuse too.

OH, the OEM line was on a 25 amp fuse. Got tired of buying them.

AC clutch has a hidden diode to ground on the positive feed wire near the compressor clutch!
 
Last edited:
Ecomike said:
The 90 Renix blower does not go through a relay. It goes through the ignition switch, Red wire in, brown wire out, which also runs the turn signals, wipers, and radio. I forget what else is loaded on it. Electric windows too on mine I think.
I ran a new 10 gauge wire from the back of the fuse box, with a 30 amp fuse to a dash mount toggle switch on my 87, 3 years ago. I have a 10 gauge wire that runs straight from the blower to the battery with a big battery clamp running the blower on 85 currently. It has a 30 amp fuse too.

OH, the OEM line was on a 25 amp fuse. Got tired of buying them.

AC clutch has a hidden diode to ground on the positive feed wire near the compressor clutch!
Click to expand...

I was pretty sure the blower was ran through the ignition switch without a relay. I was talking about the compresser.

Since it has a hidden diode.. im guessing its not as simple as upgrading the wiring...
 
Muad'Dib said:
I was pretty sure the blower was ran through the ignition switch without a relay. I was talking about the compresser.

Since it has a hidden diode.. im guessing its not as simple as upgrading the wiring...
Click to expand...

Right, it also goes through a realy IIRC. I would leave the compressor wiring alone, and focus on the blower wiring, which has real, serious issues for sure.

Nothing like loosing the wipers, and blower power on a coldfront, humid rainy day when the WS fogs up on a nice long highway drive home!:eek:
 
As for the compressor this is my idea...

The compressor has what i would call "Y" wiring on it. Where the two wires join into one there is a male "bullet" that is easily disconnected. The female end is the 12v supply from the AC relay. Looking at wiring diagrams, this runs a few different places including the OEM fan relay (and diode cluster for the oem fan didnt know that)... so it would make since to me that there would be a considerable voltage drop through this circuit.

Last night i was checking resistance across wires to see if any were bad and everything checked out well below 1 ohm except for the AC clutch power wire. I checked resistance between the relay socket and the female bullet. I cant remember now off hand how much it was... but it was definetly more than 1 ohm. I have the feeling though that this is because of all the different places that one wire runs to...

Anyway my plan was to use this female bullet to power the coil side of a relay to send 10 gauge 25 amp fused 12v directly to the male bullet (which goes to the compressor) This way we would not be eliminating any of the existing wiring, and having to deal with the diode that is near the compressor. We would be just giving it a direct feed of power.
 
Not to hijack your tread but you seem to have the wiring figured out for the ac system...

The problem I'm having is that I can't get any power to the clutch. I ran a code reader and it came back that the ac relay and aux fan relay is bad I tested both of them and they work just fine. I do know the fan will not kick on when the motor is hot are even when you turn the ac on. The po hooked a jumper wire with a switch to get the ac clutch to work, but I do not want to do that. I used a voltage tester and there is voltage at the low pressure switch.

I'm lost checked all fuses and relays
 
Muad'Dib said:
Huge hijack!!

Anyway, what year are you dealing with? It sounds like you may have two seperate issues. One being a bad fan motor. The other possibly being a bad low pressure switch which is a common problem.
Click to expand...

Gotta love troubleshooting multiple electrical problems. Only thing more fun, is troubleshooting multiple INTERMITTENT problems!:D
 
I just tried disconecting the harness from the clutch and with the engine running and ac system on full blast I was only getting .06 volts from the wire... would theis be enough to switch a relay on.
 
You two guys (Muad'Dib and recycledxj ) are pulling my leg right?

No 0.06, 0.6, and even 6 volts will not turn on the compressor clutch. It takes about 8-9 volts minimum (I actually tested it once, but it varies with the plate gap, which is adjustable). Not sure what the minimal voltage is on the relays, but they designed for 12-14 volts.

Muad'Dib, I am SHOCKED at you! It takes voltage to get shocked! :laugh3: All joking aside, with out voltage, there is no current.

I (current) varies with V voltage

I also varies with R, Resistance.

V = I*R

Given a fixed, constant resistance (or impedance), the voltage is proportional to the current. No voltage, means no current, no current means no voltage.

And 550 ma is .55 amps, the small relays we use probably pull about 30 to 50 ma at most. If you don't supply enough voltage, you don't get enough current to pull in the relay, or clutch.
 
;)

Ecomike .. i understand ohms law and watts law very well.. but the question was asked if a given voltage would trigger a relay. That question could not be answered because there are too many variables. But what we do know is that a relay requires approx .5 amps to be triggered. So thats the answer i gave ;)


Now that this thread has been hijacked.. i still havent gotten an answer to my question on the previous page....

Muad'Dib said:
As for the compressor this is my idea...

The compressor has what i would call "Y" wiring on it. Where the two wires join into one there is a male "bullet" that is easily disconnected. The female end is the 12v supply from the AC relay. Looking at wiring diagrams, this runs a few different places including the OEM fan relay (and diode cluster for the oem fan didnt know that)... so it would make since to me that there would be a considerable voltage drop through this circuit.

Last night i was checking resistance across wires to see if any were bad and everything checked out well below 1 ohm except for the AC clutch power wire. I checked resistance between the relay socket and the female bullet. I cant remember now off hand how much it was... but it was definetly more than 1 ohm. I have the feeling though that this is because of all the different places that one wire runs to...

Anyway my plan was to use this female bullet to power the coil side of a relay to send 10 gauge 25 amp fused 12v directly to the male bullet (which goes to the compressor) This way we would not be eliminating any of the existing wiring, and having to deal with the diode that is near the compressor. We would be just giving it a direct feed of power.
Click to expand...
 
Last edited:
Muad'Dib said:
;)

Ecomike .. i understand ohms law and watts law very well.. but the question was asked if a given voltage would trigger a relay. That question could not be answered because there are too many variables. But what we do know is that a relay requires approx .5 amps to be triggered. So thats the answer i gave ;)


Now that this thread has been hijacked.. i still havent gotten an answer to my question on the previous page....
Click to expand...


.06 volts wont do shit on any electronics or relays I have ever seen. If V (.06 V) and R (resistance, or impedance of the relay) are fixed, I is fixed. There are no more variables.

I still say it is more like 0.05 amps, not .5 amps on our relays.

Anyway I get your point, we now return to the nolongerhijacked OP question, for which I don't the answer.:laugh:
But I think the diode is in that wire you are talking about, and it runs to ground, to bleed off the reverse pulse caused by the collapse of the magnetic field of the clutch when it is powered down. It might be affecting your ohm reading too.
 
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