Hello, I'm trying to repair an AC system on a friends 2004 accord and need some suggestion.

Problem: Turn on AC and compressor nor the fan engages.

Investigation result: Unplugged the AC pressure switch, shorted the plug, and both compressor and the condenser fan kicked on. AC blows cold but didn't measure the temp with a thermometer. Unshort the plug disengages the compressor and the fan. Hooked up my manifold gauges and they read 70 psi on the low side and 100 psi on the high side. Evacuated the system follow by a recharge resulted the same; high side is pegged at 100 psi. Compressor does not make weird noises while the plug is shorted.

From what I understand, this sounds like the compressor is failing even thou it does engage if shorted and makes no nasty noises.

Could there be anything else that's causing this?

I do not have 2004 Honda accord service manual so I have no idea how to fully diagnose this problem.

Suggestions are welcomed. Thank you so much.

Oh btw, I actually had a hard time recharging it. Even if I force the compressor to kick on, it does not like to take a charge. I think I can only get 8 to 10 oz of 134a in there.

 

You say that AC gets cold when you jumpered the hi/lo pressure switch. To get cold requires more compression and lower pressures than 100/70 psi. Are you sure your gauges are measuring correct pressures?

There is enough pressure to cause the hi/lo pressure switch to close and actuate the compressor. Since it does not, I would check that hi/lo pressure switch is showing open circuit. If yes, it's faulty and must be replaced.

Low system pressures are another issue IMO. This could be a failed expansion valve (stuck almost open). I had this happen once on my 94Ex. New expansion valve (actually bought used evaporator) fixed problem.

I would fix the hi/lo pressure switch and check my manifold gauges to be sure there is no issue there. I once had a blockage in the low pressure connection valve that caused strange pressures.

good luck

 

The manifold gauges I have are working properly.

A working AC system from a 2008 Acura TL



This one below is from the 2004 Accord after I force the compressor to engage by jumping the ac pressure switch.



When I disengage the compressor while the engine is still running, low side pressure rises to 50 psi. High side pressure never moves and pegs at 100 psi.

I honestly don't know what is going on. I feel that the compressor is doing its job but at the same time don't want to tell my friend to spend the money to find out. I know the low side pressure may look low but the freaking thing just don't want to take a charge whether I force the compressor to turn on or not.

 

I just want to be clear that prior me trying to recharge it, the first pressure reading I got from this AC system is 100 psi on the high side. No matter if the compressor is forced to engage or not, the high side pressure hardly changes. What would cause the high side pressure to be pegged like this?

 

Did you check the hi/lo pressure switch? It apparently is inoperative from your earlier checks.

It now appears the low side is going quite low, < 20 psi w/ hi side at 100 psi. These pressures suggest a low charge.

The equilibrium pressure of a static system (compressor off) is about equal to air temp in degF, unless the engine is fully warmed which will elevate the static pressure to perhaps 150psi or higher.

When compressor goes off, pressures should equalize w/i a few mins to same hi and lo pressures. Is this happening?

good luck

 

I did not check the hi/lo pressure switch yet because 1) I have to take the bumper off 2) Jumping the switch did not solve the problem so I did not focus on that. I will do so tomorrow when there is light.

When compressor is disengaged, pressure does not equalize.

 

Not equalizing (make sure pressure gauges are both zero'd) suggest a blockage in the expansion valve or possibly the receiver/drier. Any history of leak sealants or multiple re-charges?

However, w/ a blockage the compressor should go very high and low side very low. Since it only gets to 100 psi, the system charge may be low.

Strange behavior. I think you'll need to open system and investigate to resolve.

good luck

 

Thank TexasHonda for your suggestion. Just a quick update here.

The static pressure does equalize, it takes 10 to 15 min.

I measured the ac pressure switch with my multimeter and the circuit is definitely open. (There is enough pressure in the high side to close the circuit)

I was able to recharge the ac by jumping the ac pressure switch to engage the compressor and rev up the engine. The more I rev, the higher the high side pressure went, and the more charge it was willing to take. I maintained 40 psi on the low side while charging and stopped the charge when the high side reached 210 psi.

I guess there are now two problems:

1. Ac pressure switch failed
2. Ac compressor internal is failing

Errrrrr

 

Taking 15 mins to equalize is positive for blockage somwhere. Not sure if compressor is scroll unit or piston, probably scroll. They seem to have a few more problems than the older piston compressors. Some 2004 TSX's have had significant problems w/ scroll compressors. Your Accord may have same unit (TSX also has 2.4L 4-cyl).

Suggest discharging and removing receiver/drier to look for blockage (check ability to pass air). You may need to `remove/replace the expansion valve to clear the blockage. I don't know how difficult this job is on late model Accords, hopefully not too bad.

good luck