Hi All, need to replace heater core on my '77 F150 no A/C 351m. Looking at parts online I'm seeing choices with High Output heaters...how do I tell if I have High Output option or not?

Thanks.

 

The only output difference I have seen was embossed into the plastic dash bezel. It said "HIGH OUTPUT HEATER" and the one I had in a 78 was way more out put than the non high output. As far as telling, if the dash bezel doesn't say, then I guess you have to dig deeper. Mine had all same appearance as the standard just performed better, no noticeable difference. I know the actual heater core dimension is bigger on the high out put but to tell you have to disassemble to measure. You might runn it on high and compare to another truck, Mine was noticeably more air and heat, Other than that maybe the blower motor on the firewall would tell you something, keep digging.