Is there a cabin temperature sensor on my '99 E250 and where ? Just trying to narrow things down. Just curious.

I think the problem may be the blower door actuator. AC runs good. I just put my yearly can of freon in about 3 weeks ago. I think the output temp is in the 50's - near 60 deg.

Every few minutes when on Max AC the vents go to low air flow and warm for about 20 sec. Then the AC returns to normal.

Any insight would be helpful.

 

Hi Steve,
Low freon (OK, refrigerant). The evaporator is probably freezing the moisture on the coils and limiting airflow. Once the evaporator floods with freon and warms up, the ice melts, airflow returns and the temps go cool. You will probably notice a lot of water when you park. You can look for frost under the hood on the AC tubing leading into the evaporator.

Your yearly leak may have gotten worse requiring a couple of cans to top the system off.
jim

 

Yes I have noticed more water under the vehicle. Today it caught my eye more so.

I'll look at the ac components under the hood tomorrow.

May try a can of stop leak or a dye charge ??? Its near 100 deg here this, and next week.

I'm researching pulling a vac and how that works. I really don't want to spend $200 on a vac unit. I had a 93 E150 I replaced all the AC parts - did not pull a vac. Just charged it up - ran fine. I'd like to do it right this time if I need too. I need AC.

Thanks for taking time out of your busy day to post.

 

Glad to help. I'm retired so except for keeping a 27 year old E-150 running (28 hour a day job) so I have spare time. :-)

If you have an air compressor, these work well enough for the price:
Vacuum Pump - AC Vacuum Pump w/ R134A & R12 Connectors

Sometimes you can get it all sealed up, purge with gas, then take it to a shop that will pull a vacuum for a fair price.

If it is just a bit low for now, I would add a can with the stop leak in it and that should make it through the summer. Autumn is a great time to do AC work, not summer.
jim

 

Will do. I didn't know HF had that. I saw their other vac units last week. I have air comp.

 

Here's a YT on using the HF vac you mentioned above.

 

The fitting he cut was for a gauge set, not the can adapter. Without a gauge set, working on AC is just hit and mostly miss.

One important item that many folks miss is the importance of holding a vacuum for 2 hours, minimum. The vacuum removes the air but it is the moisture in the system that causes the problems. Water, R12, and heat created acids that eroded the needle on the expansion valve causing AC failure.

I would run the compressor for 30 minutes until the vacuum bottomed out, usually 25 inches on a venturi block is good. Shut off the compressor, watch the gauge, if it creeps up, it could be residual gas from the purge building pressure, not necessarily a leak. Run the compressor a bit more and recheck. When it holds for 15 minutes, let it sit the 2 hours. Be careful to avoid letting any air back into the system before recharging the gas.

It ain't tough, just tedious (and LOUD from all that air exiting the venturi block!).
jim

 

Here's some pics of the AC lines just a few minutes ago. AC on MAX - blower Max - output temp I'd say ~55 deg - ambient air 85 deg

There's definitely a water build up on the lines. Don't know if it is normal. I didn't see any icing. Just finished about a 10 min drive.

 

Condensate water on the metal lines is OK. With the medium temps and high humidity in your area, water will collect on any cold surface.

Have you got access to a gauge set to check high and low side pressures? That would nail down a low gas level quickly. The key is the sudden reduced airflow from the vents and after a while the airflow returns. When that happens, if you switch to medium heat on the selector for a minute, then back to Max AC, the airflow and cooling should return quicker.

Another item that can be the problem is the pressure sensor on the evaporator input that switches the compressor clutch on/off. If that sensor is stuck on, the pressure into the evaporator drops below the point where ice forms on the evaporator, blocking airflow. A gauge set will quickly point out that problem.

The cheapest thing at this point would be to button up the vehicle, run the system at MAX AC with the engine at higher than normal idle, then start adding a can of gas. It the compressor starts cycling ON/OFF at about 10 second intervals, that should do it. Again, a gauge set is invaluable in testing the system but this is the next best option.
jim

 

Let me play the crabby old man a short while here---best part is I'll step away immediately after!

This sounds more like a vacuum air flow control situation rather than the A/C system having issues. This of course assumes there are no other symptoms such as the same air flow un-commanded changes even when in heating or vent mode?

I fully and completely agree with Jim all this fiddling about on that system without knowledge and/or tools is a shot in the dark, potentially more harmful than helpful. While I understand budgets simply dumping refrigerant into a system can cause more expensive issues, sooner rather than later.

If A/C is important finding the source of your refrigerant leak should become a priority----IMHO anyway.

So there ya go----proceed as you will and best of luck shooting in the dark!

 

Yep, I'm looking into the blower door actuator and related vac hoses - operation, cracks.

Looks like I'm going to get some gauges pretty soon.

During my look yesterday, the AC clutch at Max AC runs continuously at least at the curb for the 5 min or so I was looking. Maybe I need to put on Norm to see if it cycles off ?

I recall in previous years the clutch cycling off - too much - and less so when I added gas.

 

Rapid cycling of the clutch is the first sign of low gas. Low side pressures after the system has stablized are roughly 22 to 40 PSI. MAX AC recycles the air in the cabin allowing for quicker cool down; no hot outside air coming in. NORM brings in outside fresh air but it has to be cooled so the system works harder.

Always run MAX AC and max blower speed when charging refrigerant. Measure the temp at the vent closest to the evaporator, and run the engine at high idle. I usually have a water hose handy to spray the condenser and a coffee can full of 100 degree water to put the refrigerant can into as it cools off from the gas being drawn into the system. Pull the can out and shake it to speed the gas going into the system, you will see the low side gauge peak when ever the can is shaken. That is normal.

When the can is empty (shake it and put it in the water, the gauge won't move), wait for the low side pressure to get as low as possible, then close the valve on the can. With luck, you will only have 22 PSI in the can to waste.

Good luck.