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A/C Control Head & Fuse #9 Problem

Heating and Ventilation

Vehicle Information: Year: 1981; Engine (size, modifications): 4.4? no mods; Total Mileage: 57345; Transmission type: Manual;

About 8 weeks ago FUSE #9 began failing routinely. The devices affected are back-up lamps, rear window wiper, and A/C (disabled the remote mirror adjustment a while ago). The Fuse would not blow immediately when replaced, but would behave normally for a distance of one block to several miles. My mechanic could not find any problems with either the back-up lamps or rear window wiper circuitry. So we removed the A/C control head. I drove the car for four weeks and almost 400 miles and Fuse #9 never failed in that time. Now thinking that the control head needed replacement, I bought a remanufactured unit from 928 International. We installed that, operations normal for about six blocks and the fuse failed! I called 928 Int'l and they suggested measuring the current draw by the compressor clutch, as excessive current draw could fry other things in the circuit, such as the fuse or control head. I'll follow up with our findings, but there's no reason to expect other than the normal 2-3 amperes.Is this a known problem, and someone has a fix? Are there other diagnostic steps that I should take? What are your suggestions for eliminating this frustrating problem?

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