I became interested in heater and A/C blower motor resistor networks for late model Corvairs recently, mostly because I wanted to find one that worked well with the higher-output heater blower motor installed in one of my Corvairs. (I found that the stock resistor network produced output that was anemic, especially on the Low fan speed. The network is bypassed on High.) Corvairs with A/C use a second blower motor, with higher output, but began sharing the resistor network with the heater blower motor beginning in 1965. (This higher-output blower motor is similar to what is available now to replace the heater blower motor.)
Note: I use the word “network” to denote that they contain more than one resistor and they are sometimes used together. (EMs have separate resistor networks for the A/C blower. FCs with a gasoline heater also use a resistor network.)
I conducted some parts book research and scoured the Interwebz to purchase a few networks that might be applicable for LM Corvairs. Some electrical testing was clearly in order, following in the footsteps of Cliff Tibbits from an article in the Fall 2007 Cool Air newsletter. (Many thanks to my friend Chris Henkel for setting up the test configuration.) The load applied to each resistor was a replacement high-volume motor (Four Season 35383, aka PM134) with plastic fan. Also, I allowed each resistor to warm up before measuring, so that the values were relatively stable.
Informal testing rig. Note two meters so that volts and amps could be measured simultaneously.
The attached screenshot below from Excel shows the testing results. Note that I tested two examples of one of the networks.
Below is a summary of my research. But first, two implications that jumped out at me:
- If you want a new LM Corvair w/o A/C resistor network (3866429 / 3929053), Four Seasons 20446 or Standard Motor Products RU776 is likely a good choice, but only if you have an original-type motor rather than a high-volume replacement.
- If you want a substitute for the usually-unobtainium resistor network for Corvairs with A/C (and also good for Corvairs with a high-volume heater blower motor), you could try 3929055 to improve performance on Low, at the cost of making Medium much worse). You’d need to fabricate an adapter for this resistor network though because the board is too short to fit properly.
Group 8.855 (P&A 34, November, 1967, p505)
P/N 3866429
1965-68 Corvair w/o A/C
Group 8.855 (P&A 34, February, 1969, p8-22)
P/N 3929053
1965-69 Corvair w/o A/C
3866429 entry (P&A 30H, January, 1973, p145)
USE 03929053 07-68
Group 9.275 (P&A 34, February, 1969, p9-23)
P/N 3866430
1966 [FS] Chevy w/ C.A.C. [Car Air Cond.]; 1966 Chevelle w/Acc. Air Cond.; 1965-68 Corvair w/Air Cond.
P/N 3929051
1967-68 ALL w/Acc. Air Cond. (exc Corvair)
P/N 3929055
1967-68 [-72] Chevelle, Camaro, [FS] Chevy, [Truck] w/C.A.C. [Car Air Cond.] (exc. Corvair)
Notes
Parts & Accessories (P&A) 34 catalogs initially covered just Corvair but grew to include Chevy II, then Chevelle, and then Camaro. P&A 30H is a Parts History index of part number changes, substitutions, and discontinuances.
3929053, the part that replaced 3866429 for the ’69 model year, does indeed have similar characteristics and is likely to be indistinguishable in real-world use. 3929053 is available as Four Seasons 20466 and Standard Motor Products RU776. However, I have not yet tested either of them to verify that their values are in-line with the NOS part.
3866430 is essentially unobtanium and I haven’t found an available part that has resistance values that are even somewhat close.
3929055 is available as an exact repro from OER / Classic Industries. However, the backing board is not as big so would need some sort of adapter to fit a LM Corvair properly. Also, its behavior is similar to the LM A/C resistor network on Low but is similar to the LM non-A/C network on Medium, so caveat emptor.
Photos
Used 3866429 on left and used 3866430 on right
Four Seasons 20485 (repro of 3929051)
3929053 NOS
3929055 exact repro (note shorter-width backing board)