Rear A/C Question...

[MonTex]

I discovered that my van (with rear A/C) has previously been converted to R-134A <sniff>. That said, my van's A/C turns on, and the compressor clutch engages OK. So, I set-out to re-charge the A/C after discovering that it was just barely cooling. I have a set of gauges that initially read that the system was 'low.' I vacuumed/evacuated the system, all held vacuum all night. Re-charged with two cans of R-134A into the system, watching my A/C guages and the thermometer in the center air vent, the system slowly took its charge. High-side settled at 220 psi, low side at about 35. Cooling efficiency was below par, and would only cool to about 60-Deg. F. out of the front vents. The rear A/C was ON, the fan continued to blow only ambient temperature air while the front was cooling somewhat OK (but at only 60 F). Initially, I figure that my compressor is compromised and in need of replacement (and parhaps some other A/C parts. My system took only about 1/2 normal freon quantity for high-side pressure to get to 210~230...with low-side pressure at about 35. I did not use any freon that had sealant in it, and do not know if it had any sealant installed prior to my owning the van.

My reach-out to the forum members concerns the fact that my rear A/C is not blowing 'cool' air as the front vents are. I opened the rear A/C access panel - the fan was blowing, yet no cool air coming from the vents - the air was ambient warm. In this rear access panel, I saw the "expansion valve" and what looks like a 'high' pressure port. Consulting the A/C schematic in my Toyota manual, I do not see this 'high' side pressure port, nor do I see any troubleshooting verbiage pertaining to the rear A/C not blowing cool air.

I could guess that the expansion valve for the rear A/C may be bad, and/or this 'high' side port may need to be purged <?>. I initially drew a vacuum at -30 Hg and it held overnight.

Can anyone offer a suggestion(s) here? I am perplexed as to why the front is blowing cool, but not the rear. Aren't the front and rear A/C all the same cooling circuit?

[Burntboot]

MT - Hopefully Tim will chime in with some useful info.
Meantime, here is what little I know---

But both evaporators run off the same compressor, so if you have cooling in the front and not the back, it is likely due to a blockage
in the system rather than ability of the compressor to pump.
In the world of Jags, expansion valves were notorious for getting plugged up.
I was also taught that any time the system was opened the rec-drier should also be replaced.

That said, if it were me, I would probably evacuate the system and replace the rear expansion valve, then refill and retest.
A/M exp valves are cheap and while their quality is likely comparable to their price, when you are trying to evaluate a system of
unknown condition, that was converted by someone else, it only makes sense to go cheap until you know what you have.

Once you determine whether the system is viable, then you can plan on replacing the appropriate parts to bring it up to snuff.

I did notice the manual recommends pulling the condenser to replace the rec/drier but that just sounds like asking for trouble.
When I had my rad out, it all looked very accessible at that point, so I would be tempted to get at it that way rather than disturb
lines and mounts at the condenser.

R134 does not cool as well as R12.
But if you can restore proper function, it should be adequate.

[timsrv]

[MonTex]

Thanks, BB & Tim for weighing-in on this. Radiator coming out tonight for inspection, cleaning/rodding-out, pressure testing, paint. It looks OK from the outside, but am running at 1/2 temp gauge scale when idling and 3/4+ scale, but still in the normal/white zone) when pulling a long hill (with A/C off). My A/C sight glass is dark brown, so I am unable to see any bubbles. I will replace the receiver/dryer, sight-glass and the rear expansion valve as soon as the parts arrive. There seems to be quite a price range with A/M A/C components. Denso (OEM vendor?) seems to be the most costly.

Regarding the radiator, mine has factory foam weatherstripping (?) on top and bottom length of the radiator core. Has anyone replaced these foam strips? Any suggestions for a suitable substitute? I assume that these foam strips are in place as dust/engine compartment shields.

[MonTex]

Got my radiator back from the shop today. It was in relatively good shape - no leaks and good flow. They repainted it too.

I asked about a re-core from the current 3-row high-efficiency core to a 4-row high-efficiency "desert radiator" core (which is the exact same core that you may have read about in other places/forums on this topic). Turns out that the existing high-efficiency 3-row core is the best way to go. Here's why, according to the owner/operator of my local radiator shop who has been in business for 20+ years and is consistently rated with 5-stars on Yelp!:

The 'desert radiator' 4-row high-efficiency core can be installed using the existing radiator tanks. However, these cores do not permit the use of the same amount of solder on the tanks as the original configuration. As a result, the 4-row 'desert radiator' is less reliable and often leaks - due to the reduced amount of solder that can be used around the tanks.

Also, the recommendation is to use ONLY pure water under 'high-pressure' to flush the radiator/cooling system. Use of the citric-acid-based commercial 'flush' loosens the material in the cooling system that will/does get caught in the radiator's cooling tubes. The recommended coolant is Prestone brand "all-makes/all models" ethylene glycol (yellow) because it is the latest new formula and works best with aluminum and cast iron engine components.

If anyone is interested in the 4-row core 'desert radiator' using the exact same core that you have read about elsewhere - PM me. The radiator shop local to me can/will make the same radiator for over $100 less than the 'other' radiator shop. I called the 'other' referenced shop in Northern California and got a (rather pricey) quote.

See the attached paper regarding cooling fans....and standard vs. heavy-duty/super-duty fan clutches...