Engine Bay heat when A/C is running

[55trucker]

This might be a question for those of you who are southern based where you use the A/C on a regular basis......

 

if you drive a W that was originally an R-12 car but has been converted to 134 have any of you noticed an excessive amount of heat build-up in the engine bay when the A/C is in use?

 

Last year I did the conversion seeing as the R12 compressor gave me headaches where the control valve was not sealing.....there's nothing wrong with the compressor I just could not get the control valve out to service it.

 

I installed a new 134a compressor & a new condenser as well as a fresh accumulator & an orifice tube for good measure. Everything with the exception of the evaporator core came out of the car & all components including the evap core that went back in were flushed clean of the mineral oil & PAG replaced the mineral oil. All went back together with no issue, the system drew a vacuum & I recharged it, the system cools but I notice that the center vent temp will NOT drop below 50F regardless of what the ambient temp outside is. The fans cut in as should do & I've been driving the car this way for just about 12 months now.

 

What IS unusual is the amount of heat build up in the engine bay now when the A/C is running. It's so hot under the hood that in the right side electrical center the fan relays are roasting as well the other fuses in there, the 2 engine bay support struts are too hot too touch & the rad header is the same. One can feel the intense heat coming thru the cores when the fans are on.

 

Before the conversion I never had this sort of issue, and I'm wondering if anyone else is seeing this same situation........

 

 

 

 

Steve

[jman093]

I really doubt there's any issue with too much heat. It's how any car I've seen is. If you think about it, on a hot summer day after everything is fully heat soaked, the coolant itself is going to be in the 215-220 degree range, and anything metal in the engine bay is going to be warmer than that, so yeah, stuff may be too hot too touch. Only thing to check is to make sure the coolant operating temp is normal and the fans are both working.

 

As far as the AC not working well, it's kind of the nature of conversions. R134 is simply a crappier refrigerant compared to R12 (and fwiw, R134 is now being phased out by even crapper R1234-yf). The system ideally needs upgraded with more efficient components, but there are a couple things that might help.

 

First off, you may be overcharged. Less refrigerant is specified on a conversion. GM's formula is: (R12 amount x 0.9) - 0.25lbs.

Secondly it's common to switch the factory orifice tube with the "Ford blue" one on a conversion. The orifice is slightly smaller and supposedly helps get more cooling. IIRC, I've done it on both my TGP's and both cool decently. Not R12 good, but good enough.

[RobertISaar]

I think with a V5 compressor(which is going to be what's on most 1st gens), the low-side pressure is used to modify stroke length, so instead of a more significant pressure drop(and the lower temperature that would come with it) due to a smaller orifice, stroke will increase to keep it the ~35PSI or so it targets by raising high-side pressure further.

 

with enough airflow over the condenser, it might not cool that much worse, but the compressor and everything on the high-pressure side is going to experience more stress.

[Schurkey]

What are the high- and low-side pressures?

 

What is the coolant temperature sensor showing for coolant temp?

[55trucker]

Doing the test *by the book* on the given day

 

ambient is approx. 74F, humidity approx 50% ....engine has run for 10 mins, windows closed, A/C set to norm, blower on high, engine rpm 2000....

 

center vent temp is at 58F (will NOT drop below that), suction side pressure is floating at 45psi, discharge pressure is floating at 270psi.

 

with the scanner running at the same time the engine temp is fluctuating at 199-201 degrees, primary fan is engaged almost constantly (as it should be where no vehicle motion is detected)

 

according to my 91 R-12 diagnostic charts the system IS in the *white area* of the graphic chart, the discharge side is getting close to the border, but that is an R-12 chart, I would like to see what the later R134a for 95 or 96 has to display.

 

The manual would suggest that under these conditions the air handling system is at fault but all the necessary doors have been checked to make sure they are closed. The only other item stated would be the compressor control valve, (suction side pressure is well above 35psi)

 

The system was charged with approx 10% less volume for the 134a refrigerant.

 

according to a sourced 134a pressure/temp chart at 270psi the refrigerant temp is at near 155 degrees ( that would be thru the condenser)

[Schurkey]

I have some concerns about the high low-side pressure.  45 psi seems excessive.  270 psi on the high side also seems high given the ambient temperature.

 

High high side, high low side might indicate over-charged refrigerant.  But don't take my word for it.  I suppose it could also be a result of an ineffective (plugged) condenser not transferring heat properly.

 

What happens to the low-side pressure and duct temperature if you spray the condenser with a garden hose?

 

 

 

 

For the record, I had to change the fan clutch on my Trailblazer a couple of weeks ago.  While I had the fan and shroud out, I blew compressed air through the air-fins of the radiator and condenser.  HOLY CRAP what a dust-storm that created.  And now the A/C seems to work better.  The funny thing is, I never noticed that the condenser was plugged with dirt.   It looked fine--until the compressed air hit it and pushed all the dust out.

[Imp558]

I know it's not a fix, but for the sake of not baking all the vacuum lines and wiring maybe you should remove the rear rubber Hood seal buy the cowl until you get everything sorted out.I haven't had a seal on that in a long time and it brought my underhood temperatures down considerably.

[Schurkey]

...which is strange since the rear hood seal is intended to keep air from entering the engine compartment.

 

Think about all the "cowl induction" hood scoops, that bring high-pressure air from the base of the windshield into the engine compartment.   Then consider that EVERY GM OEM application used rubber or foam seals to prevent that high-pressure air from escaping the carburetor/air cleaner and getting into the engine compartment.

 

The OTHER advantage of that hood seal is that it keeps engine compartment fumes from entering the HVAC system--because the HVAC system also takes advantage of the high-pressure area at the base of the windshield.  You got oil from an oil leak onto the exhaust manifold smoldering and smoking?  You'll be more likely to smell it in the car if the seal at the back of the hood is removed.

[Imp558]

Daily driving in stop and go traffic there has to be far less time where that is actually a high pressure area. Before I took it off it was hot under the hood, it was uncomfortable to touch even the strut towers. After the hood seal came off they are barely warm. I know the passenger fresh air intake is there in the cowl, and why but my car not being total smoldering shit pile under the hood I don't have anything burning off.

I did it in 2009 or 2010.

[Joee]

Hello, is there any update for this prob? Im having the same prob now. And i belive that is not normal. Maybe someting wrong with the ac compressor or clutch.