Mikailhaq

Hey Guys - Picked up a 96 4.9 XLT a few weeks back. Not sure what to make of it, all in all looks like a beauty minus a few little dings - paint is beautiful... undercarriage is pretty rust free, but there has definitely been some jimmy-rigging, i.e. the oil cooler that was hanging in the grile, and by hanging I mean, a the bolt on a clamp was wedged holding it in place.. both hoses disconnected.

It was running decent until the Alternator went earlier in the week. I swapped it out and it was back to running fine. Yesterday I hopped on the highway and felt like it didn't have the pickup it should. When I would hit the gas I'd still hear the blower, but the AC seemed to switch to the defrost vents, and stop coming out the vents. All in all it wasn't quite as cold as it usually is. The AC is frigid typically.

I just gave it a complete tune-up (Oil/Filter, fuel filter, plugs/wires/rotor/cap) and a quick flush with new coolant as I replaced the lower hose.

I haven't started her back up since I am fussing with the oil pan gasket, but while I am down here is there anything else worth checking/replacing?

My ODB II wasn't working - Cig lighter/charger was, but I swapped the fuse which was blown so i should be able to get it scanned at advance auto parts once I am rolling about again... but anyone familiar with these types of hickups?

Brandon587

The ac thing is a vaccum leak somewhere, it could also be your power problem. As far as the obd port, the only time mine hasn't worked is when the fuse was blown.

Mikailhaq

Thank you kind sir. Im gonna spray some starter fluid around the elbows and such that have rotted into dust once shes running again (if she is running again, gasket!!!)

Mikailhaq

Swapped fuse, port still not reading.. AC still cutting back when accelerating. Truck is running dramatically better, but still seems to be a draw with AC on blast.

I am noticing that the MAX AC fan or whatever the little bell looking thing is by the heater hoses is actually disconnected - my heater lines have water running through them, as I see the return pour back into the radiator, but I most definitely do NOT have heat

memoniz

Brandon587 is correct about the vacuum leak for the a/c. The white vacuum line under the hood, passenger side firewall, is generally the culprit for that. The white vacuum hose which controls the air flow on mine is brittle and had a leak. I cut it shorter, added a new connector, and now works fine.

If that " bell looking thing" is on your heater box, then that is the actuator that controls a/c flow and that needs to be connected to the vacuum.

When I use my a/c, it draws a lot of amps from the alternator. I have replaced my alternator several times. I just realized that is the way it will be unless I buy a more powerful one.

fltdriver

With multiple problems like this anything not in person is just a guess.........

Follow the wires from the OBD port and look for damaged wires or bad connections, could be computer related as well.

Not sure what you mean by the bell looking thing, would go out and look at mine but it's raining pretty hard here, if it's the blend air module (which is the only thing I can think of that is right there) it needs to be hooked up. I believe this could also be the cause of the switching to vents at highway speed and your no heat issue.

Make sure the temp selector is working properly and that the blend air door is functioning. If both are working as they should and still no luck, you can remove the heater core hoses and flush it out to ensure there is no blockage, I did this when I replaced the water pump but am sure you can do it with the pump still attached.

As for the power loss at higher RPM's, which is counter intuitive, only thing I can think of is the alternator that you put in is either faulty or doesn't supply enough power. Check grounds and connections first. Clean up the grounds with emery cloth (frame, eyelet, get the bolt with wire brush), get the connector with QD electronic clean, and ensure all wires are corrosion and wear free with good solid/clean connections. OR... did you put the correct amp alt in? If you have a lot of electronic draw the 130 amp would almost be mandatory.

I'm starting to wonder, as I'm typing, if you don't have belt slippage or even a bad ac compressor. It could be one of many things causing your issues. Start be repairing what you know to be wrong, once you have done that, pull your codes. Get a voltmeter and google the specs for your truck, start with the alt and ac and ensure they have proper signals.

Mikailhaq

Thanks for all your input brother. I should have clarified its not so much a power loss as it sounds bogged down when the AC cut off.

The compressor is cold, that I know as it pools out underneath and blows frigid. The belt seems fine... I imagine this all originates from that region of the engine by the AC blower... its clearly been tampered with.




I can hear the blend door or what have u move when i push the arm of this "pump" back and forth... question is, when I put the hose on this.. where does it run to?!?!!?

fltdriver

That's what controls the blend door, runs on vacuum. I will get a picture of where the lines go in a few minutes.

fltdriver

Connected to blend door actuator




Enters wire loom




wire loom is closest to actuator, goes through grommet/firewall.




View through glove box, white hose dead center of screen, behind everything else




Connects to plastic piece directly below ash tray.




Then to the back of your climate control center.

Mikailhaq

I love you...

Let me relax and soak this in, then grab an exacto knife to carve out all the silicone someone caked over those hoses.

Im assuming 7/64th vac hose works in palce of those plastic hoses, but how do you manage the connections/t's and such.

I just had something break off the top of the blower assemply, I shoved it inside a piece of hose then connected it.

Will grab pics when I drag my *** back outside