Jim Lane

Augie Dog,

Shutting off the coolant would defiantly make a difference, checking NAPA for your truck shows there should be a vacuum operated valve there already.

Make sure your vacuum system is working properly also if the blend doors do not work it will suck in the outside air instead of recirculating the cold inside air.
I forgot to reconnect the vacuum line and it would not get below 40* but after I realized what I did and reconnected it the temperature now gets down to 25*.

http://napaonline.com/masterpages/NO...n=Heater+Valve

Tinting your windows would help somewhat with the heat but it is not a cure-all, the closed up truck is still a big oven with the door closed.
What color is the interior? Is there a headliner? You could completely insulate the cab from roof to floorboard like I did.

If your truck was a gasser then you probably would not have had the extra heat shielding that belongs on the firewall unless you took it from the donor truck there is also shielding on the floorboard for the heat radiated by the exhaust.

What did you use to recharge your air conditioner R-12, R134a?
Cool air in the morning or when it is cool out and then having problems once it starts getting hot out is also a symptom of having moisture in your AC system.
Do you remember about how long was it evaporated or pumped down?

Jim

BearKiller

I plumbed in a standard (metal, not plastic) 1/2" ball-valve, in the top heater-hose, for positive control of the hot coolant to the interior.

I noticed a huge difference, as soon as I next drove it.



Another A/C robbing culprit is the sometimes-work/sometimes-not fan-clutches on these engines.

A direct-drive, or pinned, clutch will really cool down the A/C, especially when the truck is still, or moving slow.

After wearing out my tools, taking back bad clutches, I pinned the clutch on the wife's truck; now, it cools like it should, and there have been no ill effects from the loss of the clutch.

BearKiller

I am definitely a dummy , when it comes to A/C.

Should an A/C system be evacuated/vacuumed and recharged on a regular basis, even when all the mechanicals work fine??

If so, how often should this be done??

When the A/C shop sucks out the old, is it just put back in, or disposed of??

Thanks.

wannadiesel

One thing to keep in mind about the factory valve is that it only shuts off coolant flow to the heater core in "off" and "max A/C" modes. In all other modes coolant is flowing through the heater core.

AUGIE DOG

Thanks for the reply Jim, the vac valve you speak of in the line has been removed. I am also having a problem getting heat in the cooler months. I installed a new t-stat. and all that works properly. I am guessing the blend doors are not working the way they should. The system was serviced about a year ago and they used R134a. I had the a/c installed from donor truck since my truck was non a/c. The technician did have a problem with a valve in the system but they repaired it and all is well. I do need insulation as you spoke of and that is one of the things that will be added as i continue to rebuild this truck.

BC847

Should an A/C system be evacuated/vacuumed and recharged on a regular basis, even when all the mechanicals work fine?? No

If so, how often should this be done?? Only when the refrigerant circuit is opened.

When the A/C shop sucks out the old, is it just put back in, or disposed of?? If the refrigerant is contaminated, it is sent off for recycling. Most shops are of the attitude that refrigerant is always replaced as that's more money to be made.

AUGIE DOG

Bearkiller, Where did you get the valve? Is that a Lowe's or Home Depot thing? As far as my fan clutch working ......WELL i don't think it is. I have never heard it cycle like people on here talk about. Thanks

BearKiller

Any plumbing/hardware store should have it.

I bought a bunch of them, real good looking, at HarborFreight one time, on sale for next to nothing; they were superior to the much more expensive ones that came from the local plumbing supply for about five times the money.

Jim Lane

Re. Compressor cycling.
After checking the wiring diagram for out trucks there is no way of modulating the temperature by cycling the compressor on and off by a thermostatic setting, it is all done by blending the hot air with the cold.
If working properly the cycling switch only will cycle the compressor to off if it senses an evaporator freeze up, and this in not user adjustable.
So we should never hear the compressor cycling on our 1st. Gen trucks.

I am also having a problem getting heat in the cooler months. I installed a new t-stat. and all that works properly. I am guessing the blend doors are not working the way they should.

Is your engine vacuum pump working properly?

Jim

andyr354

Got ya, understand why you need the two now.

I tried a jumper on mine last night and it speed up some. I only had a 16g wire for my jumper and wow, it got hot fast just supplementing the existing power wire. Doing this mod should take allot of load off the ignition switch and the interior wiring.

speaking of doing away with the resistors and going to a PWM found this in a quick ebay search.
http://www.ebay.com.my/viItem?ItemId=120134403643

AUGIE DOG

Jim, I'll be honest about the vacum pump and say I DON"T KNOW !! I've been concentrating on getting the front end swapped out ,trans. upgraded and switching rearends i've not paid attention. It doesn't get real cold here in the winter so i have just been dealing with it for now. Also is there a way to check if blend doors work? When i turn heat on vent and then to floor or defrost there is a delay but it does switch. It also does it with a/c.

Jim Lane

That is great that you can see what I am talking about. Now imagine all of that current being supplied by the tiny contacts in the ignition switch and you can now see why they are always melting down to a puddle on the floor.

My blower on Hi speed is drawing around 17 amperes through the 10ga. & 12ga. wiring straight from the battery, the actual current will also be dependant on how much backpressure there is on the blower. This is also why you need to upgrade the ground path for the motor because if you don't do it then all of your work could cause it to burn out the weakest link, which would be the ground connection.

That is a good link for the PWM controller; most people do not even have a clue what you are talking about when you start using acronyms, PWM, PB&J.

I currently have a few I got from this company; I use them for some robotic controls on a project I had built. I had shorted out a Hexfet on one and she overnighted me a new controller the next day 3 days before Christmas.

http://www.diverseelectronicservices.com/html/mc7.html

This is a link to the home page, they are real nice people.
http://www.diverseelectronicservices.com/


I used the MC-7 although this one is bi-directional it would work fine for our blower motor and the speed could be controlled from Zero to full speed with a small 5K linear taper potentiometer.

For those who do not understand PWM, the motor always has 12 volts supplied to it but the speed is controlled by how fast the 12 volts is pulsed from off to on state hence the name Pulse Width Modulation, this is a very over simplified explanation of course.
With PWM the motor has full torque available at its first revolution up to full speed.
This is why it is so good for robotics control.

Sorry getting carried away again.
Jim.

BearKiller

This is way out in left-field; but, could one simply wire in a BIG ground, then run a relayed HOT that is triggered by the fast speed wire at the fan-speed control (or a toggle-switch), thus giving relayed full speed, when the switch is on HIGH??

Not the best set-up, but would get most of the load off the ignition switch, until time could be found to do your wonderful modification.

Would this work??

Thanks.

Jim Lane

AUGIE DOG,

How are your power brakes? Do they seem to assist properly? You could connect a vacuum gauge to the line and see if it will hold a vacuum. The vacuum for the AC controls is the small 1/8" tube that exits the firewall where I drilled the hole for the wire and connects to the brake booster. You might have a check valve leaking or something, without seeing it this would be a guess. Which vacuum pump do you have? Your engine is a 91.5 so you have the rotary pump correct?
When I get a chance I will check and see which servos move when the controls are switched.
Jim

Jim Lane

BK
Yes this would work but if you follow the wiring diagram you will see that there are also fan connections for the regular AC and heater, which is where the feedback was coming from.

A simple toggle switch would work but you would need to turn it off when you stopped the truck or at least trigger it from the ignition circuit.
But you would only have HI speed when it was on.
The reason I did it the way I did was so it would mimic the intended controls yet remove the full load from the ignition switch and internal wiring.

until time could be found to do your wonderful modification.

But for a temporary fix I think it would be ok, you could just mount a FUSED 30 amp relay by the blower and trigger it from the ignition circuit through a toggle switch in the cab.
I would make a check on the wiring and be sure it was sound enough to handle all of this new current back fed to it.

Jim