searcher

I'm sorry to bring this post back up, but I have to correct my earlier post. Only the '89 doesn't use the cycling switch. The '90 has it. I should have checked instead of assuming they were the same.

Silver

After replacing all the switches, draining the compressor, and vacuuming the system for hours the AC was tested again. The pressure still went high. The question of the fan clutch kept coming up so we got a new one. Put it in, started it up, and presto... the **** thing worked like it should. It cycled on and off perfectly. My buddie was overjoyed... I know he was getting tired of working on it.

Being fairly good at being the "Devil's Advocate", I revved the engine a few times and told my buddie to watch (I knew what would happen)... the engine was not hot enough to keep the fan clutch locked and the couple revs were enough to free it up and make it "coast". Immediately the pressure started climbing. He looked at me like I had shot him. It got to about 400-450 psi, but it did finally cycle. I don't know if this is the way it's supposed to work, but it does blow cold air and it cycles normally when driving down the road. I will be very cautious for a while when idling with it on, but it is a heck of a lot better than it was.

Some parts of this project are still a mystery. If anyone has the answers, I am definitely interested.

dpuckett

So, you mean I just need to jump the Blu/Wt and Brown wires and it will bypass the bad cycling switch? It CANT be that easy.

But, what will this do to my selecting a temp other than ice cold? Or will I just have to put it on A/C for a while, then vent, then A/C, then vent? This is of course, to keep my cooler natured girlfriend from freezing (she cant snuggle up to me, as I dont have a bench seat), and not for my personal comfort

Daniel

NoSparkplugs

Yeah Dave it can't be that easy can it? Wait I guess it can be, I got my A/C system to work decently with a new relay on the drivers side fender. It just doesn't to want to cycle the compressor from what I can see. How long does it take for the compressor to cycle on then off? Maybe I'm not waiting long enough?

wannadiesel

It is that easy.

The temp is still controlled by the temp lever. Just slide it a little to the right if things get too cold, that will make some of the air blow through the heater core.

The compressor shouldn't be cycling unless - 1: you are low on refrigerant, causing the low pressure switch to stop the compressor. 2: the cycling switch determines that the evaporator is in danger of freezing up. Otherwise the compressor ought to run whenever A/C or defrost is selected on the control panel.

frostie

Yes folks its that easy. I just did it to my truck last week. I bypassed the computor box and the cycling switch. Grounding the little blue and orange wire at the relay kicked my A/C on and worked good. That blue and orange wire goes to the computor box and comes out brown and goes to cycling switch. I soldered the blue and orange to the brown near the relay, then soldered the blue and white to brown at the cycling switch. It is so nice. One time in the past week I had to move my heat lever to hot for just a moment to thaw out my evaporator and back to cold.

92red

--So, you mean I just need to jump the Blu/Wt and Brown wires and it will bypass the bad cycling switch? It CANT be that easy.--

Well, I tried this tonight by running a jumper between the wires but without cutting them. Is that where I went wrong? Do I need to cut so that the jumper completes the circuit before the wires go into the switch?

Thanks,
Mike

Jim5870

Will I achieve the same result if I pull the probe out of the hose?
(assuming that my cycling switch is working)

QIK2D

i have had 2 brand new aftermarket driers cause very similar problem. somethine inside the drier acts as a reed and holds freon in the drier. one of my techs says he's seen it on several occasions. he evacuated the system and disconnected the hoses on each side of the drier and then struck the drier with a wrench and freon came flying out. damnest thing i've ever seen. new drier fixed it right up. not saying thats your problem but if you have your system pulled down again, try it.

daryl

schamran

Jim: This is off-topic, but what would cause my AC to freeze up. it only happens when the truck isn't moving, and the fan clutch, etc, is good. It starts making a whistling noise, and there is an awful smell. I turn it off now every time I stop, but I don't know how to fix this. Thanks.

whosdunit

jim, if i can still get the origional cycling sw., (for 91 non/ ic) w/ the probe where & how much???whosdunit.

Jim Lane

This was about 2 years ago from my local Dodge Dealer however I do not know if they are still available.

Temp Sensing Switch P.N.#56005783 (mounted on H block) $64.88
Jim

whosdunit

I tried my local parts house, no luck,your relay fix sounds good to me. Again thanks to folks like you & Faith,& this forum we can keep these old trks., going. thanks Whosdunit.

whosdunit

JIM, I have 2-wires(1-solid brn 1- solid blue) that come from a/c comp. they tie into plug w/2 # 10's (1-alter-1-batt)
the solid blue & brn. are beside the blue /white they are the one's that plug into the cycling plug.
of the 3 blk wire's on the up side of cycling plug (this is w/clip side up).
I tied the out side (brn) to the rt. side (blue/white stripe - wham! a/c came on - stayed unit I pushed off in cab.
what's wrong with this set up? Should I use fuse between brn & blue/white? Say 20 amp???

Jim Lane

Buried deep inside the cycling switch there is a relay that switches the compressor clutch, on a non-intercooled model there is no external relay and all of the current and arcing would be handled through the contacts of the inside controls.

The relay would greatly extend its life.

If yours were intercooled there should be an external relay on the fender that handles the compressor cycling.
I think.

Faith?

Jim