I just did a weber carb install. Got the new kit and it works great. However, now the AC clutch wont kick in. I unplugged and removed a bunch of emissions stuff over on the battery side of the engine compartment. I did not remove any wiring but just tucked it in front of battery behind the headlight. Is there anything over there related to the AC system operation that I need to plug back in? I also unplugged and removed the computer under the kick panel. Is it possible the AC relay was accidentally removed? Where is it supposed to be located?

 

The AC relay is on the evaporator case, under the dash on the passenger side. For now I would concentrate on an electrical issue, and not even bother to check refrigerant "static" pressure (static pressure must be high enough to "close" the pressure switch and complete the circuit). I also have a Weber on my B2200 (since back in 2005) and AC, and I also just disconnected the wiring harnesses on passenger side fender area and wrapped those up. The computer under the kick panel should not be involved, but mine is still in place and plugged in.

Does the blower fan operate in ALL speeds? Because the blower resistor is involved in the compressor clutch circuit. History has shown that the little push-in switch on the dash can go bad.

There's at least one 10-amp fuse and one 15-amp fuse in the AC circuit (see below), check those.

I doubt that you removed/knocked off a wire off the drier pressure switch, as that's somewhat hidden by the truck body. Also doubt that you disconnected the wire to the compressor itself.

Normally, I would work backward from the AC clutch on the compressor, which most likely is NOT getting 12 volts positive or AC clutch would engage; so work backwards from there and find out where the 12 volts positive is NOT getting through. Don't panic, and don't fret, you can figure this out.

NEVER ADD ANY SEALANT OR REFRIGERANT CONTAINING SEALANT, YOU CAN RUIN THE SYSTEM PERMANENTLY !!!! Note bold and CAPITALS !!!

 

Thanks for the reply Cusser. I previously had the issue with the blower resistor and it’s been replaced already so yes, the blower works in all speeds. I’ll go through the check points you suggest and report back.

 

Ok I wiggled the connections at the low pressure switch on the drier and it started working. I’ll get the grill off for good access and clean those contacts up.

it blows cool but kinda weak. I think it may need a shot of Freon. A previous owner must have already converted to 134a because those fittings are already on the charging ports.

I could do a complete evacuate and recharge by weight but I’d rather just carefully add a little and see if it responds. What type of low side line pressure should I be looking for on a fully charged system while I’m running mode? I have full gauge set and a big tank of 134

 

That's what I would do.


I assume that you mean weak to be not as cool, not that less air is coming out the vents, correct? Yes, your system would now be R134a. Technically, an underhood sticker should've been applied to the underside of the hood stating this.


"If" I was topping off (and I've done so on my Frontiers), I would not rely on low side pressure for this. I would shoot for high side pressure of 230 to 260 psi at about 1800 rpm if the outside temperature is maybe about 90F. Never add any sealer or refrigerant containing sealer, and I've seen pure R134a at $5 a can at Home Depot and at Walmart. Note that newer R134a cans have a government-mandated no-leak valve now, so a special adapter must be purchased (about $3, parts stores like Autozone or O'Reilly). I wouldn't add more than 6 ounces refrigerant to start, and remember to purge the service gauge lines of air.

Yes, a "tad" of refrigerant will leak past any compressor seal, so even a "real good system" can need a few ounces of refrigerant a decade.

 

Great info Cusser, thank you. I'll post back with some pre and post charging measurements

 

Also discovered the AC relay behind the glove box is randomly sticking. AC wasn’t coming on and I tapped the relay with a wrench and it came on.

 

Well this little truck is forcing me to get familiar with every little part of it. I think I've nailed the culprit. Its the dash mounted switch. The way i read the wiring diagram, this switch when pushed in is supposed to close the circuit and create a ground that triggers the AC relay to send power to the compressor clutch. Well, after removing and bench testing Im getting no continuity through this switch whatsoever in any position. Ill run a jumper across the connector tomorrow and see what happens.

Can this switch be disassembled and possibly repaired?

Otherwise i suppose i could put a standard toggle in

 

Yes, this push-in switch is a weak spot. 5 of the 6 I pulled at the parts yard a decade ago tested bad, wonder how many B-trucks were junked because a "mechanic" told the owner that the compressor needed replacement? Anyway, I fixed those 5 bad switches, and sold them.So these can be cleaned out/repaired. AC push-in switch repair (Mazda # UB39-61-550)
http://www.partsbase.org/parts/mazda-ub3961550/

http://www.jimellismazdaparts.com/products/Mazda/SWITCH--AIR-CONDITIONING-AC/1917301/UB3961550.html

http://www.atlantamazdaparts.com/p/SWITCH--AIR-CONDITIONING-AC/42724390/UB3961550.html

The test is that there should be continuity between the LY and LW wires (blue/yellow and blue/white) when the switch is pushed in. I figured out (again) how to take these apart. I think the key is to remove the two tiny bulbs first, then push in the two little tabs, then gently pull/pry out. Inside, not too complicated; if one takes apart the switch carefully with the light bulb side down, then pretty straightforward to see how everything should go. There are two metal contacts which might have some old grease on them. On the switch part itself is a little U-shaped piece of metal that completes the circuit between those contacts when the switch is pushed in. There's a spring which pushed the button rearwards; there's also a little spring which operates the push-in-push out mechanism. So once it's cleaned, put back together, slide the housing over it, put the bulbs back in place, test for continuity between LY and LW wires again when the switch is clicked down. I also cleaned the contacts for the bulbs with a little steel wool, some were dirty, others nice. So 30 minutes to do the first one, then 5 minutes each to repair the other four, typical for stuff like this. And one OK as well initially, and I cleaned/fixed the one I kept for myself while I was at it.

I took both bulbs out of the switch I retained here, and the switch still worked fine. The 1991 Wiring Manual (Diagram G on page Z-68) actually shows the switch without the two bulbs and with only 3 wires, guess Mazda figured those should be in a lighting circuit diagram or something. My '88 Service Manual shows 5 wires and two 1.4 watt bulbs. So I think that although a switch failure can cause a clue by having the light not illuminate (like when mine was bad in 1995), a burnt out or missing bulb is not enough to cause the system not to operate.

 

Fantastic information Cusser. I’ll try and repair this switch. Thanks again!