First thing to do is pinch off the hot water supply to figure out if a/c is underperforming or heater is overperforming.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

Thought about it but I don't like to pinch those off because replacement of them is difficult with the M120 in place. May try to disconnect and plug.

__________________
To see my 129 parts for sale visit:
http://stores.ebay.com/The-Mercedes-SL-Store
John Roncallo

Tomorrow/today I will test my stock 560SL that had a new Bosch monovalve installed 3 years ago to see if I get the same level of heat bypassing in the hose.

__________________
To see my 129 parts for sale visit:
http://stores.ebay.com/The-Mercedes-SL-Store
John Roncallo

Well whatever it is its getting worse Like 64° today. I wasn't able to try my stock 107 because my wife had a list of chores for me to do. But I am leaning towards the monovalve because even the outlet of the heater core is hot which should be being cooled by the evaporator. I even did try to pinch it off but my pinch pliers are really too short for the hoes diameter.

I did order a new monovalve, Its not MTC but a company allegedly as bad. Vollig - Heavy Duty But who knows, maybe they got this part right.

__________________
To see my 129 parts for sale visit:
http://stores.ebay.com/The-Mercedes-SL-Store
John Roncallo

Results are in for the moment. It is not the monovalve because I completely blocked it off. I took the line off and plugged it. 60° duct temp with the monovalve blocked off.

Interesting results with a stock 560SL this morning. The stock 560SL with R12 charged 3 years ago. I turned it on high blower temp came down to 46°, low blower temp down to 36°. Checked the monovalve hose and it was cool. Turned the heat on full to open the monovalve. Monovalve hose got hot. Tuned the AC back on again high blower, couldn't get the temperature below 54° and about 44° with low blower. Monovalve hose remained reasonably warm. It might have gotten better if I let it run for a while but it takes a long time to cool down that heater core. Apparently monovalves do have some leakage, at least 3 year old ones do.

So the modified 560SL also is a little cooler with the system plugged but not much.

I'm getting a little concerned that possibly I did damage to the system when I installed the aux fan. My first install had the fan spinning backwards canceling out what the radiator fan was doing. I drove the car about 5 miles before I realized something was very wrong. AC would not work at all, coolant temp was running high. High side pressure probably tripped the 390PSI pressure limit, assuming the switch worked. They are new Behr switches but I am able to tell that the fan pressure switch, is supposed to turn on the low speed aux fan at 290PSI is turning it on at 230PSI, so maybe the compressor cutout switch is also off. The system has been compromised ever since I ran with the aux fan backwards.

In any case I will leave the mono valve plugged to take it out of the system until I get this sorted. I will have to wait until my recovery system comes in to do any more with charge.

__________________
To see my 129 parts for sale visit:
http://stores.ebay.com/The-Mercedes-SL-Store
John Roncallo