1991 Ford F-150 ac issues, advice please

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1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Mon Aug 22, 2016 4:16 am

I have a 1991 Ford F-150 lariat, with the 4.9l inline six and automatic transmission. I bought the truck not running and have been getting it back in good order. The HVAC system is giving me fits and I need advice. I had originally replaced the compressor with a remanufactured one, new dryer and red ford orifice tube, the entire system was solvent flushed, vac'ed down and charged with r-134a. It never worked well and I tried adjusting the charge from lower pressures (35 low, 200 high) up to (45 low, 250 high). I was never able to get good cold air at the vents. I have made sure that the vacuum system and all blend doors are working properly. The system was filled with 10 ounces of ester oil. I began to get curious about other refrigerants so I pulled the system down and flushed it again, I found a little debris in the orifice tube so I replaced the compressor, dryer and orifice tube with new. I flushed the system, vac'ed it down and then charged with 10 ounces of PAG 46 and industrial enviro safe which is a hydrocarbon refrigerant. It blows coolish at idle and the pressures are about what the company recommends at 35 low and 175-200 high. I feel like the charge may be wrong but I'm hoping someone has dealt with this before and may have some advice. The truck has dual electric pusher fans in addition to the engine driven fan. I also note that the compressor cycles fairly frequently at interstate speed, which I would think indicates a low charge, but adding more refrigerant would push the pressures up too high. I'm about at my wits end and am considering paying to have it charged with r12.
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Mon Aug 22, 2016 9:12 am

Go easy messing with assorted refrigerants and forge the lie about "enviro safe" crap. If those were any good they would be use in something new and never have been.

IDK - This set up isn't even difficult so something changed isn't working out. Rebuilt compressors usually stink and you've found debris so that's high on you problem list.

It's old - what is still OE about it? Condenser? Pusher fan - why? This should have a perfectly good fan and fan clutch that worked fine and small cab to cool.

It's cycling and meant to for certain situations.

Pressures mean nothing if you don't observe temps exactly and conditions at the time.

Real temps needed. Incoming air temp thru grille and real center vent temp at what RPM or observations mean little.

Did you add pusher fans and leave belt driven fan? They could fight with each other and mess it up. IDK - one style or the other not both is my suggestion.

R-12 scares everybody about cost of it still available. Why oh why does perhaps at full cost $150 bucks if that much make everyone rethink some other type of anything now when this was meant for R-12?

BTW - you could be off quite a bit with R-12 on charge on this if all was right and get good performance. You wont with alternatives and at best get 80% BTU cooling power of R-12 without jumping more hoops not needed in this vehicle with a small cab IMO.

It's old - so be it but leaks around parts/components probably messing things up?

T
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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Mon Aug 22, 2016 1:15 pm

The currently installed compressor is a new one, as far as what's OE on the truck only the condenser and evaporator are original. I always thought more fans were better for ac but maybe not? I'm going to call around and get a price on an r12 charge, can PAG be used with r12? Or would I have to flush it again and change oil? Is the red orifice tube sufficient?

Thank you
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Re: 1991 Ford F-150 ac issues, advice please

Postby jas88 » Mon Aug 22, 2016 4:04 pm

If you are seeing 35 low and 200 high that might be optimal as far as pressures go, but there are other factors you left out. What is ambient temp? What is fan speed set on?

Are you sure about your heat/cool blend door? On your truck, if you slide the temp bar from hot to all the way cold quickly, you should hear the blend door slamming shut if it is set correctly.

What are hose temps (by feel) on high, low side and liquid line? If you are 35 low, your evap return line should be cold. If it is, I suspect your blend door is not operating correctly. If it is not cold, then your gauges are lying to you I think, or you are undercharged, although 200 high would say no to that.

BTW I also have a '91 F150 I converted to R134a about 10 years ago, and I agree with Tom, this is a very simple system. Your use of the pusher fans should alleviate the need for an R134a condensor, which my truck has.
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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Mon Aug 22, 2016 4:41 pm

I actually disassembled the air handling portion this morning to verify the foam seals are in good shape and the blend door and fresh air doors are operating properly. Oddly enough I pulled the pusher fans off and am getting better temps idling and at speed, I'm still concerned about the orifice tube size as I have a red one installed but this refrigerant is supposed to behave similar to r12 so I'm wondering if I should switch back to the blue orifice tube that the system would have had from the factory?
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Mon Aug 22, 2016 6:14 pm

This was out of order for a while - sorry folks - think fixed now.

Just some notes for now:

*No you can't use R-12 with PAG oil, use mineral with R-12.

*Yes you can have too many fans or they fight with each other and get LESS flow not more.

Think - if always more fans pulled more air propeller airplanes would line them up - doesn't work that way.

Some blades are variable pitch and some not the same pitch so you get a messed up area even a vacuum perhaps in between.

Also remember what air comes in thru a grill must also exit not just move around in engine bays. Air dams - the things under front bumpers create a vacuum at some speed even not that fast so flow is down and out back. Sitting still if not right some could push hot air up front again!

Question anything altered from OE designs. If new they failed you really hope it was caught but some things get by that could have done better always know the cheapest way to make something work will rule if it works,

T
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Re: 1991 Ford F-150 ac issues, advice please

Postby jas88 » Mon Aug 22, 2016 10:17 pm

If you were getting insufficient air flow across the condensor, I would expect higher pressure than 200, tho, unless you were undercharged, then all bets are off.

Fans do not always fight each other, I used to have a 1990 F150 that had an electric puller fan hooked up to run only when the a/c was on, in addition to the factory fan, and it worked fine. The puller made the a/c work better when the truck was in traffic and idling a lot in the Texas summer heat.

Those pusher fans could be a problem, but I don't think that is the problem. I need more info (see my previous post) to help any further.

WRT orifice tubes, use red for R134a and blue for R12.
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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Mon Aug 22, 2016 11:10 pm

Changed to a blue orifice tube, recharged and I'm getting pretty good performance. I suspect that a switch to dual puller fans instead of the factory setup will provide the best result. During recharge with the blue tube I was at 38 and 215 pressures, 95 ambient. The tube immediately after the orifice was getting down to 46-47 from what I could measure with a non contact thermometer. I'm not sure the thermometer that I have stuck in my vent is the most accurate, what would be recommended for vent temp measurements?

I have something like this:
http://www.webstaurantstore.com/5-probe ... 3T220.html
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Tue Aug 23, 2016 12:54 am

Image

If that shows says it's for food. Just smaller than some like it for A/C.

What should vent temps be you ask? It can vary by all conditions at the exact time you check.

I like faster digital wired remotes you can put down inside a center vent. Almost anything should get you low to mid 40sF depending on fan speed requested from actual air temps outside of about 75 - 100F or so. Humidity, sun light and how long you've run it all count.

Some very large vehicles or some just lousy designs (not too many) you'll only see 50sF. If you can't get into the 40s with some regularity something isn't right. This is a 1991 which just age you can forgive some efficiency loss of plain dirty exterior of parts and some air leakage around items that should seal tighter.

Converting doesn't really change output temps but does change the BTU or volume it can continue to put out lower temps when stressed as it's only 80% the caloric value of R-12 from the beginning. Components are made to exchange heat that 20% more to compensate if all correct.

In a small cab of a truck the original was most likely overkill so shouldn't notice much difference except I notice converted vehicles are a bit slow to achieve max performance.

I'd get a thermos that's larger and meant more for A/C than the one shown just because. Touchless or infrared can be funky with checking non solid items probably best to really get used to each one and their quirks first. Compare readings of equipment to something known if possible - even gauges for pressures can be way off, some adjustable some not,

T
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Re: 1991 Ford F-150 ac issues, advice please

Postby ACProf » Tue Aug 23, 2016 1:54 am

MAKE SURE the pusher fans are indeed PUSHING air in the correct direction! I've had cases where the pusher wires were hooked up backwards and were actually blowing air toward the front of the vehicle. In this case they impede the air flow through the condenser and the system works better with them disconnected. Sound familiar??

If the direction is wrong, just reverse the wires on the plug.
Sometimes you just have to accept things at faith value!
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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Tue Aug 23, 2016 2:02 am

They were definitely pushing, i suspect they probably created more obstruction then the added cooling could overcome. What I did do is seal up the gap between the condenser and radiator so it will be forced to pull air through the condenser rather than around it. The temp gauge didn't run any hotter idling in the sun so I suspect my cooling system Is healthy. I'm going to order a better thermometer tomorrow so I can get better temp readings.
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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Tue Aug 23, 2016 11:51 am

Well, it was cooling great. Idling in the garage this morning it blew a line, very exciting. It looks like the push in fitting separated, I have no idea how, I'm guessing the auto parts store quality isn't as good as motorcraft? I did notice that the spring is now missing, but wasn't when assembled. I heard it click as it always has. Back to square one...
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Tue Aug 23, 2016 12:08 pm

Hmmm - 1991 - I think all used a lot of "Spring Lock" connections relying on a spring to hold it. NEW they should have had a U type clamp as a safety such that they wouldn't separate. You can probably find those used on assorted real Ford products or ask for new ones.

I don't think it can separate with those in place. Maybe leak but not come apart.

Should be easy enough to fix, add some oil guessing by mess it made, vac and charge per specs and be all fine again with new O ring always suggested.

Bad luck - should be relatively easy to take care of,

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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Tue Aug 23, 2016 12:18 pm

Scared the hell out of me I can tell you that much! I just pushed the line back in for now to save the dryer, it was new.
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Tue Aug 23, 2016 12:44 pm

If exposed just cover it with plastic, foil or something on open ends with twisty ties. That should do.

Wish I could find a picture of those "u" holder things that don't allow enough movement for a separation.

It's like a double horseshoe type thing you might think was for a brake part or something.

Not funny and yes scary - refrigerant let loose all at once can be quite the display if witnessed,

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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Tue Aug 23, 2016 12:50 pm

See if I can make the thing show I'm talking about..........

https://encrypted-tbn1.gstatic.com/imag ... eYniDhnE4Q

Not direct but should show if you click on that........


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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Tue Aug 23, 2016 1:09 pm

Yes, that would have saved me from this mornings display, luckily no one was around when it happened.
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Tue Aug 23, 2016 1:30 pm

Glad that showed and would have been OE but may have broken along the way over the years. Just a back up so that doesn't happen in your hands or face while working on a system.

Ford used these for years and many redone under warranty when new for the "O" ring probably not lubricated well enough as they can twist and hold refrigerant so a wear spot.

Have them on my own and now and then lube with plain silicone spray as if that helps - it might as it's older than this and they don't leak.

Have had a crimped sealed cap on small can of refrigerant part pull off just tapping it and tossed it and tap in one dang hurry out of my way spinning around like nuts, frosting the pavement while releasing gas in seconds. That would be a serious freeze burn up to a skin graft if in my hands!

Watch out for this stuff like a lot of things,

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Re: 1991 Ford F-150 ac issues, advice please

Postby mtrosclair » Tue Aug 23, 2016 2:06 pm

I was looking at the end of the tube where the orifice tube goes in and it looks kinda buggered up, I wonder if it was damaged when the hose blew off? I guess I'm going to have to change the evaporator because its part of that assembly?
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Re: 1991 Ford F-150 ac issues, advice please

Postby Tom Greenleaf » Tue Aug 23, 2016 3:02 pm

Sure could have been. Replace if damaged or it will probably leak even with clip thing now,

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